Neuroscience Test Iii

Front 1

1. What are the functions of the cerebellum?

Back 1

Guardian Angel (or the busy manager)
Cerebellum occupies 10% of the brain’s total volume—yet it contains >50% of all the neurons in the brain.
Participates in all classes of volitional movement—skilled reach/grasp, locomotion, and balance postural control--through its outputs to the thalamuscortex and to brainstem nuclei that modulate the activity of upper motor neurons and motor planning regions.
Cerebellum learns from mistakes: Motor learning by adaptation--learning from errors in order to make the next movement correct.
Also involved in non-movement functions: cognition/executive functions, language, emotion/affective function, and visual-spatial processing.
General tonic output from the cerebellar pathways is excitatory to both thalamic and brainstem targets (compared to the basal ganglia which has a tonic inhibitory output to its thalamic and brainstem targets). Regardless of where pathways cross—cerebellum will have ipsilateral effe

Front 2

General function: Guardian Angel /The busy Manager—
The role of the cerebellum is to make it possible for us to adapt the ______ coordination of our movements quickly to the context in which the movement is occurring

Back 2

General function: Guardian Angel /The busy Manager—
The role of the cerebellum is to make it possible for us to adapt the spatial/temporal coordination of our movements quickly to the context in which the movement is occurring—the prism lens and the scooter board experiment.

The cerebellum watches over or monitors your every move to see if you make a mistake like losing your balance or missing the target with a throw. It may implement a correction during the movement (if there is time) but more importantly, it makes sure the next move is better than the first by using the information from the mistake to provide predictive feedforward control to help you to adjust the next movement. This function allows you to adapt the movement to any situation/context. You end up making less mistakes the next time because the adaption is triggered by the mistakes/errors. With the prism experiment--observed adaptation to the visual stimuli of the prisms and de-adaptation when the lens were remo

Front 3

While it most likely is not correcting your movement while it is going on (other regions will do this such as the spinal cord and brainstem) the cerebellum is using that info gathered to influence

Back 3

While it most likely is not correcting your movement while it is going on (other regions will do this such as the spinal cord and brainstem) the cerebellum is using that info gathered to influence the next movement and its outputs to the upper motorneurons in the cortex and brainstem sets the gain of those systems which can be viewed as the bandwidth of accuracy for effective performance.

Sets the gain for reflexes and automatic reactions so that they are matched to the environmental context (for example, balance reactions to repeated perturbations will become modulated to the amount of perturbation--think of Nora on the skateboard/longboard). Sends that output to premotor and motor cortex and brainstem centers to tune or set the bandwidth of responses thus modulating their direct influence on the alpha motor neurons and interneurons. The Cerebellum modulates volitional movements Postural control, distal limb, locomotion, eyes (this list is the same for the basal ganglia).

Front 4

General motor control/movement functions of the Cerebellum: Involved in ____ _____ ____ __ in all volitional movements (____...)

Back 4

General motor control/movement functions of the Cerebellum: Involved in motor planning, movement execution, and motor learning in all volitional movements (balance/postural control, limb movements, locomotion, eye movements)

Front 5

Motor Planning function of the cerebellum

Back 5

Motor Planning function: Coordinationfine tune the execution of movement and putting those movements in context of the state of the individual at a moment in time. Makes movement accurate in time and space across joints. Fine tune the movements within a selected movement sequence providing timing signals to the motor areas that control the contraction of muscles acting across a joint.

Front 6

Movement execution function of the cerebellum:

Back 6

Movement execution function: Comparator/corrections Comparator—compares what you intended to happen vs what is really happeningadjusts the ongoing start/stop movement such as reach/grasp or modulates/adapts a repetitive/continuous motion such as gait . Gets a copy of a central motor command (efference copy) and predicts the sensory consequence of that act during its execution—sends its output to cortex via thalamus and brainstem centers to correct a movement and to, adapt it for the next movement. Feedback correction online.

Front 7

Motor learning function of the cerebellum

Back 7

Motor learning function: Corrector Adaptation/predictive feedforward control defined: compares intended with actual, adaptive responses that lead to immediate adjustments in performance and eventual long term learning motor skills, gait, and balance/postural control. Intrinsic circuitry modifies immediately/short term changeseventually long term changes. Trial and error learning of figuring out how to do a motion that was selected based upon feedback received during the motion.

Front 8

Signs and symptoms of Cerebellar motor dysfunction are classified as “____ ______”

Back 8

Signs and symptoms of Cerebellar motor dysfunction are classified as “movement disorders”
The cerebellum is “one step removed” from the motor output—they regulate the activity of upper motorneurons; however, there are no cerebellar origin of upper motor neuron descending tracts to spinal or cranial motor neurons. Therefore, cerebellar dysfunction does not change sensation (i.e., no numbness, loss of sensation) or strength (i.e., no paresis/paralysis)

Front 9

Impairments/changes to body structure/body function with cerebellar damage

Back 9

Impairments/changes to body structure/body function:
Ataxia: abnormal execution of multi-joint motions, lack of coordination (dysmetria, disdiadochokinesia, dysarthria) but with normal strength
Movement decomposition--loss of coordination across multiple joints for one smooth, simultaneous movement (see hip, knee, ankle move separately from each other rather than simulataneous)
Intention Tremor or action tremor
Nystagmus
Activities:
Impaired balance/postural control, gait, eye motions, and limb motions

Front 10

2. What are the anatomical divisions and structures of the cerebellum? overview

Back 10

3 Lobes
3 Regions of the cerebellar hemispheres (Comparisons to the cerebral hemispheres):
Outer gray matter layer
Inner white matter tracts
Deep nucleii

3 Cortical Layers

3 pairs of Peduncles
3 pairs of Output nuclei
3 functional regions

Front 11

Cerebellar Lobes

Back 11

Cerebellar Lobes (Horizontal Divisions from rostral to caudal):
3 Lobes unlike the cerebral cortex, the anatomical lobes are not functionally distinct (except for the floccularnodualr lobe) .
Anterior lobe
Posterior lobe
Flocularnodularlobe - vestibulocerebellum

The Anterior and Posterior lobes contain both vertical functional divisions of cerebrocerebellum and spinocerebellum with a somatotopic organization. Note that the axial structures for balance and postural control are medial and the limbs are lateral

Front 12

Anatomical organization: 3 regions Comparisons to the cerebral hemispheres: Like a mini cerebrum cortex aka small brain:

Back 12

Anatomical organization: 3 regions Comparisons to the cerebral hemispheres: Like a mini cerebrum cortex aka small brain:
cerebellar cortex outer cellular layer divided into 3 cellular layers (see bottom right)
Cerebellar Cortex: like the cerebral cortex, is a single continuous sheet folded onto of itself in a rostral/caudal direction, divided into 3 lobes—which are subdivided into lobules—and then individual folia which makes it looks like an intricate leaf. The folds are much more intricate that those found in the cerebral cortex.
inner white matter axon tracts going to and from the cerebellar cortex
deep nucleioutput source from cerebellum to thalamus and brainstem centers.

TRANSVERSE PLANE CUT: identify the nuclei and the peduncle. Note the white matter relative to the darker cortical layers. Also note the intricacy of the folia folds.

Front 13

3 Peduncles of the cerebellum

Back 13

3 Peduncles: 3 pairs of white matter fiber bundles
Superior—main efferent/output pathway to thalamus and brainstem, with 1 afferent/input from spinal cord low-fidelity spinocerebellar tracts that provide info about motor plan “efference copy”
Middle—afferent/input from cortex via corticopontinepontocerebellar
Inferior—afferent/input from spinal cord, brainstem, olive, with 1 efferent/output to vestibular nucleii and reticular formation from vestibulocerebellum (does not synapse on a cerebellar nucleus first).

Front 14

3 pairs of deep Output Nuclei—source of output/efference from cerebellum:

Back 14

3 pairs of deep Output Nuclei—source of output/efference from cerebellum:
All outputs from the nuclei use superior cerebellar peduncle to leave the cerebellum (except for vestibulocerebellum)
Dentateinputs from cerebrocerebellum
Interposed (emboliform, globose)inputs from intermediate spinocerebellum
Fastigal inputs from medial spinocerebellum (vermis)

Even though the vestibular nuclei are not in the cerebellum, they receive direct inputs from the vestibulocerebellum and even some directly from the vermis/medial spinocerebellum.

 Deep nuceli receive inhibitory input from purkinje cells and excitatory input from collaterals of mossy fibers and climbing fibers.

Front 15

Cortical Layers: 3 Layers of the cerebellum
Granule cell layer

Back 15

Cortical Layers: 3 Layers (see next slide for figure)
Granule cell layer: deepest layer input layer
Cell bodies of granule cells—lots of little pebbly granules cells and a few local interneurons (golgi cells). Granule cell axons extend up to the superficial molecular layer to then lay out the parallel fibers.
Receive inputs from mossy fibers which are axons from spinocerebellar tracts, pontocerebellar inputs, vestibular inputs, reticular formation.
100’s of mossy fibers synapse on 1 granule cell (convergence of inputs)

Front 16

Cortical Layers: 3 Layers of the cerebellum; Purkinje cell layer

Back 16

Purkinje cell layer: middle layer contains output cells for the cerebellar cortex
Cell bodies of Purkinje cells—big guys. Dendrites project out and up into molecular layer, Axons descend into the white matter of the cerebellum to all of the different output nuclei (specific nuclei depend upon the functional region of the cerebellum)
Receive excitatory inputs from 200,000 to 1million parallel fibers and from 1 climbing fiber that originates from the inferior olive in the brainstem.
Send inhibitory output from the cerebellar cortex to the deep cerebellar nuclei

Front 17

Cortical Layers: 3 Layers of the cerebellum: Molecular layer

Back 17

Molecular layer: most superficial integration layer
Cell bodies of local interneurons (stellate and basket cells)
Vertical dendrites of Purkinje cells and excitatory axons of the granule cells which run horizontally long the folia to become the parallel fibers. Each parallel fiber synapses with 250-750 Purkinje cells (divergence of information). Provide a constant chatter of excitatory inputs to Purkinje cells. The axons of the inferior olive cells climbing fibers wrap around the Purkinje cell bodies and dendrite trees—send a strong error message to Purkinje cell. Each purkinje cell receives input from 1 climbing fiber and 200,000 parallel fibers.
Parallel fibers and Purkinje cells dendrites create a grid—Purkinje cells in sagital plane vertical stripes and parallel fibers in transverse plane. Horizontal lines connecting the vertical stripes to each other. Purkinje cells like telephone poles and parallel fibers are the lines between.

Front 18

Cerebellar cortex--3 fibers and 1 axon output from cerebellar cortex

Back 18

2 fibers are inputs/ EXCITATORY afference
1 fiber is internal to the cerebellum and EXCITATORY
1 axon output from the cerebellar cortex /INHIBITORY efference to the deep nuclei

Mossy Fibers: excitatory inputs

Climbing fibers: excitatory inputs from the inferior olive. Synapse on purkinje send a collateral to the output nucleii

Parallel fibers--internal to cerebellum--the axons of the granule cells that will project into the molecular layer to synapse on the purkinje cell.
Purkinje cell axons: inhibitory output to the cerebellar nucleii
cerebellar nuclei then send the output for the cerebellum as a whole

Front 19

Mossy Fibers:

Back 19

Mossy Fibers: excitatory inputs from axons from spinal cord (spinocerebellar tracts), cranial nucleii, cortex (corticopontine pontocerebellar tracts), vestibular inputs, reticular formation.
Enter through all three cerebellar peduncles. Synapse on multiple granule cells and send a collateral to the output nucleii.

Front 20

Climbing fibers:

Back 20

Climbing fibers: excitatory inputs from the inferior olive. Synapse on up to 10 purkinje cells and send a collateral to the output nucleii
Enter through the inferior cerebellar peduncle.

Front 21

Parallel fibers-- of cerebellum

Back 21

Parallel fibers--internal to the cerebellum--the axons of the granule cells that will project into the molecular layer to synapse on the purkinje cell.

Front 22

Purkinje cell axons in the cerebellum

Back 22

Purkinje cell axons: inhibitory output to the cerebellar nucleii
cerebellar nuclei then send the output for the cerebellum as a whole through the superior and inferior cerebellar peduncle.

Front 23

3. What is the cellular circuitry within the cerebellum?
PATHWAY BASIS FOR CEREBELLAR FUNCTIONS: COORDINATION PLANNING AND ADAPTATION:
Cerebellar circuitry functionselective disfacilitation of cerebellar nuclei cells by...

Back 23

PATHWAY BASIS FOR CEREBELLAR FUNCTIONS: COORDINATION PLANNING AND ADAPTATION:
Cerebellar circuitry functionselective disfacilitation of cerebellar nuclei cells by purkinje cell inhibitory input so that the population of outputs from the cerebellar nuclei can tune or sculpt and coordinate timing of actions within a movement. (like the basal ganglia, except there is a network of cells sending out a collection of messages to sculpt a collective output affecting several actions within a movement sequence)

Front 24

3. What is the cellular circuitry within the cerebellum?
PATHWAY BASIS FOR CEREBELLAR FUNCTIONS: COORDINATION PLANNING AND ADAPTATION:
Tonic output from the cerebellum is excitation—to change movement—to make an adaptation like we did during the Prism experiment—the olive detects an error in the movement produced. Through its activation of the ____ cell

Back 24

Tonic output from the cerebellum is excitation—to change movement—to make an adaptation like we did during the Prism experiment—the olive detects an error in the movement produced. Through its activation of the purkinje cell via the climbing fiber synapse, works to tune or sculpt the collective output of the cerebellar cortex network. This then changes the outputs of the cerebellar cortex to the cerebellar nucleiiand thus changes the activation patterns of the cerebellar nucleii to their targets.

Front 25

3. What is the cellular circuitry within the cerebellum?
PATHWAY BASIS FOR CEREBELLAR FUNCTIONS: COORDINATION PLANNING AND ADAPTATION: Focuses the system on the change in on/off of a muscle action within a movement so that the movement is accurate. Sets the gain of the motor system with ___

Back 25

Focuses the system on the change in on/off of a muscle action within a movement so that the movement is accurate. Sets the gain of the motor system with predictive feedforward behavior which is reinforced with accurate performance, and it becomes a new/official behavior.

Front 26

4. What are the functional divisions of the cerebellum?
CEREBELLUM: Vertical (medial-lateral) FUNCTIONAL organization: 3 functional regions

Back 26

Spinocerebellum—Medial portion vermis/vermal region:
monitor/correct motor execution axial postural set and gaze stabilize during movement
Spinocerebellum—Intermediate portion paravermal region:
monitor/correct motor execution and distal limb movement set
MOTOR EXECUTION

Cerebrocerebellum—Lateral Hemispheres:
motor planning and motor learning
MOTOR PLANNING

Vestibulocerebellum—flocular-nodular lobe:
balance/postural control, head/eye movements
BALANCE AND EYE MOVEMENT

Front 27

4. What are the functional divisions of the cerebellum?

What are the output targets?

Back 27

DESCENDING PATHWAYS MODULATION OVERVIEW:



Vestibulocerebellum & vermis/medial zone of spinocerebellummedial descending pathways in brainstem and cortex



Intermediate zone of spinocerebellum & Cerebrocerebellumlateral descending pathways of brainstem and cortex

Front 28

4. What are the functional divisions of the cerebellum?
What are the input sources to the different functional divisions?

Back 28

INPUTS OVERVIEW

Vestibulocerebellumvestibular , visual from brainstem

Vermis/medial zone of spinocerebellum visual, auditory, vestibular from brainstem, spinocerebellar trunk/axial limb tracts

Paravermis/intermediate zone of spinocerebellumspinocerebellar inputs only from limbs

Note: ventral(anterior) spinocerebellar and rostral spinocerebellar tracts provide an efference copy or info about the descending commands sent to the spinal cord circuits.

Cerebrocerebellumcorticopontine pontocerebellar

Front 29

VESTIBULOCEREBELLUM and VERMIS OF SPINOCEREBELLUM: to

Back 29

VESTIBULOCEREBELLUM and VERMIS OF SPINOCEREBELLUM: to medial descending system for balance and head motions

Front 30

VESTIBULOCEREBELLUM : FUNCTIONAL OUTPUTS EYE CONTROL

Back 30

Connections of the vestibulocerebellum in the floccularnodular lobe involved in the control of eye movements.

Outputs project to the vestibular nuclei which will use the MLF to connect to the oculomotor nuclei in CN III, IV and VI for visual reflexes and smooth pursuit motions of the eyes.

Front 31

VERMIS OF SPINOCEREBELLUM--medial zone of the spinocerebellum: FUNCTIONAL PATHWAYS for

Back 31

VERMIS OF SPINOCEREBELLUM--medial zone of the spinocerebellum: FUNCTIONAL PATHWAYS for balance and postural control to medial descending systems.

The main input to the vermis/medial spinocerebellum is
from spinocerebellar pathways as well as vestibular nuclei, reticular formation, and contralateral motor cortex.
The
medial vermis projects, via the fastigial nucleus, to the reticular formation and the vestibular nucleus as well as to the thalamus to the motor cortex.

Front 32

CEREBROCEREBELLUM and INTERMEDIATE ZONE OF SPINOCEREBELLUM: FUNCTIONAL OUTPUTS

Neurons in the intermediate zone and lateral parts of the cerebellar hemisphere project to the

Back 32

CEREBROCEREBELLUM and INTERMEDIATE ZONE OF SPINOCEREBELLUM: FUNCTIONAL OUTPUTS

Neurons in the intermediate zone and lateral parts of the cerebellar hemisphere project to the contralateral red nucleus and cerebral cortex. The intermediate zone (spinocerebellum) receives sensory information from the limbs and controls the dorsolateral descending systems (rubrospinal and corticospinal tracts) acting on the ipsilateral limbs. The lateral zone (cerebrocerebellum) receives cortical input via the pontine nuclei and influences the motor and premotor cortices via the ventrolateral nucleus of the thalamus

Front 33

INTERMEDIATE ZONE OF SPINOCEREBELLUM: FUNCTIONAL OUTPUTS

Back 33

The intermediate portion of the hemispheres (paravermis) receives cortical input via the contralateral pontine nuclei and spinocerebellar input from the ipsilateral spinal cord.

The paravermis projects to the globose and emboliform nuclei, which project to the contralateral motor cortex (by way of the thalamus) and to the red nucleus (origin of the rubrospinal tract).

Front 34

Cerebrocerebellum inputs and outputs

Back 34

The lateral portion of the cerebral hemispheres receives, via the pontine nuclei, input from widespread areas of the cerebral cortex.

The outputs from the cerebrocerebellum projects to the dentate nucleus,
which then projects to the contralateral thalamus. The cerebellar territory of the contralateral thalamus is the ventral
lateral nucleus.

Front 35

5. What the impairments associated with cerebellar lesions and how are they clinically tested?
List of impairments

Back 35

Limb movement:
Dyssynnergia
Dysmetria
Tremor
-Kinetic
-Intention
-Postural
Disdiadochokinesia
Asthenia and hypotonia

Balance and gait dysfunction:

Occulomotor:
Nystagmus
Saccadic smooth pursuit
Poor vestibulo-occular reflex cancellation
Dysmetric saccades
Reduced velocity of divergent eye movement
Abnormal vestibulo-occular reflex and optokinetic response

Dysarthria

Front 36

Dyssynnergia
Clinical tests:
Assess:

Back 36

Finger to nose
Heel to shin

Assess ability to move joints independently and dissect multijoint movement

Front 37

Dysmetria
Clinical tests:
Assess:

Back 37

Clinical tests: finger to finger, finger to great toe (support trunk to isolate limbs)
Assess:
speed of motion
variability of path
over/undershoot

Front 38

Tremor
Clinical tests:
Assess:

Back 38

Clinical tests: holding a position, e.g. 1. arms outstretched with palms down 2. index to index (hold fingers medially)
Move to/from target
Assess writing/spiriography
Assess:
Tremor amplitude/frequency
Assess for titubation ~3Hz tremor of the head

Front 39

Disdiadochokinesia
Clinical tests:
Assess:

Back 39

Clinical tests:
alternating pronation-supination
wrist flexion/extension while tapping the thigh
dorsi/plantarflexion
Assess:
Rate of movement

Front 40

Asthenia and hypotonia
Clinical tests:
Assess:

Back 40

Clinical tests:
Passive motion of the limb
Test muscle strength
Assess:
Resistance to motion
Strength

Front 41

Balance and gait dysfunction:
Clinical tests:
Assess:

Back 41

Clinical tests:
Stand with eyes open/closed
Stand in tandem/on one foot
Balance in response to perturbation, volitional upper/lower limb
Walking
Assess:
Rate, direction and amplitude of sway (+- vision) and phase between upper and lower body
Size of response to postural perturbation
Walking- accuracy of foot placement/degree of sway/time in double stance/stride length/base of support

Front 42

The basal ganglia are involved in the motor control of

Back 42

The basal ganglia are involved in the motor control of volitional, automatic and oculomotor movements as well as trial/error (i.e., reinforcement) motor learning. They are also involved in sensorimotor processing for accurate self-monitoring of movement, as well as cognition including working memory, shifting attentional focus and emotion.

Front 43

As Goldilocks—the basal ganglia

Back 43

As Goldilocks—the basal ganglia select the right behavior and simultaneously prevent the wrong behaviors.

The basal ganglia acts as a filter by looping information from the cortex back to the cortex and the brainstem. The striatum (input nuclei) integrate a variety of info from several different cortical regions to detect specific patterns of activity that warrant a response such as a movement, or attention, emotion, or cognitive process. They send their output back to the cortex (via the thalamus) or to the brainstem. The function of the basal ganglia is to select and facilitate the right response to occur, that is the right amplitude, at the right time relative to other movements (or thoughts, emotions) and in the right order—it’s “just right” as in the goldilocks principle.

Front 44

As Otto the Auto-Pilot the basal ganglia

Back 44

As Otto the Auto-Pilot the basal ganglia
Facilitate the automatic execution of selected sequential motor programs while simultaneously suppressing all other potentially competing and interfering motor programs.

Regulate initiation and termination of motor sequences, cognitive processes, emotional responses/reactions.

Interrupt behavior to favor/permit a response to a novel/behaviorally significant stimulus.

Scale amplitude/duration/force of postures and movements during the execution of a motor plan and generate the internal cues necessary to self-monitor and correct movement.

Front 45

Therefore, in motor control, the basal ganglia have a role in:

Back 45

Therefore, in motor control, the basal ganglia have a role in:

Motor Planning: Selection and Sequencing of movements especially the access of automatic, well learned movement (Otto) which frees the cortex to do other activities (necessary for dual tasking).

Motor Execution: Initiation/Termination and Scale amplitude of motions (volitional and automatic) including the generation of internal cues for self-monitoring and correction.

Motor Learning: Reinforcement learning (i.e., associative learning)

Front 46

Signs and symptoms of Basal Ganglia motor function are classified as

Back 46

Signs and symptoms of Basal Ganglia motor function are classified as “movement disorders”
The basal ganglia are “one step removed” from the motor output—they regulate the activity of upper motorneurons; however, there are no basal ganglia origin of upper motor neuron descending tracts to spinal or cranial motor neurons. Therefore, basal ganglia dysfunction does not change sensation (i.e., no numbness, loss of sensation) or strength (i.e., no paresis/paralysis)

Front 47

Impairments/changes to body structure/body function with basal ganglia damage

Back 47

Impairments/changes to body structure/body function:
Hypokinesias, Hyperkinesias and Dyskinesias
Loss of automaticity—leads to difficulty with dual tasking (i.e., walk/talk, maintain balance postural control while doing a task with the UE’s).
Impaired somatosensory/proprioceptive processing to inform motion (i.e., inaccurate perception of movement amplitude)
Activities:
Impaired balance/postural control, gait, eye motions, and limb motions

Front 48

2. What are the basal ganglia and where are they located?

Back 48

The basal ganglia are large interconnected subcortical nuclei found in three anatomical regions: deep in the cerebral hemispheres, the diencephalon, and the midbrain.

The striatum receives input from the cortex and thalamus and the globus pallidus internus send outputs to the thalamus nuclei to the cortex and the substantia nigra pars reticulata sends outputs to brainstem nuclei. The subthalamic nucleus also receives cortical input. Dopamine is projected to the striatum from the substania nigra pars compacta.

Front 49

Basal ganglia nuclei in the Cerebral hemispheres:

Back 49

Cerebral hemispheres:

Striatum: input nuclei
- Putamen (put)
- Caudate nucleus (cn)
- Nucleus Accumens/ventral striatum
receives input from the cortex and thalamus

Globus pallidus
-Globus pallidus externus (gpe)
-Globus pallidus internus (gpi)
globus pallidus internus send outputs to the thalamus nuclei to the cortex

Front 50

Basal ganglia nuclei in the Diencephalon:

Back 50

Diencephalon:

Subthalamic nucleus (stn):
globus pallidus internus send outputs to the thalamus nuclei to the cortex
STN also receives cortical input.

Front 51

Basal ganglia nuclei in the Midbrain:

Back 51

Midbrain:

Substantia nigra.
-Substantia nigra pars compacta (SNpc) output dopamine to the striatum
-Substantia nigra pars reticulata (SNpr)
sends outputs to brainstem

Front 52

2. Where are the basal-ganglia located?

Back 52

The caudate nucleus is a big C shape“tucked” into the inferior and lateral surface of the two big lateral ventricles—it has a “head” “body” and “tail.” the ventral striatum is the inferior portion of the head. The putamen is the egg shape tucked in the C of the caudate.
The globus pallidus is medial to the putamen.
Medial to the basal ganglia are the two thalami.

Front 53

At rest, the output nuclei of the basal ganglia maintain _____ output on their targets—the ____and the ____ nuclei.

Back 53

At rest, the output nuclei of the basal ganglia maintain chronic inhibitory output on their targets—the thalamus and the brainstem nuclei.

Front 54

When we want to move, for the basal ganglia to achieve their Goldilocks function:

#1: The direct pathway

#2: The indirect pathway

Back 54

When we want to move, for the basal ganglia to achieve their Goldilocks function:

#1: The direct pathway functions as a pause button on the otherwise tonic inhibition of the thalamus and brainstem to permit initiation of selected motor programs. Direct =Disinhibition of wanted motor programs

#2: The indirect pathway suppresses unwanted motor programs or even stops/interrupts ongoing motor programs to allow a new program wanted by the direct pathway. Indirect=enhances inhibition of unwanted programs.

Front 55

Basal ganglia - DIRECT PATHWAY

Back 55

DIRECT PATHWAY—disinhibition—facilitates movement
Cortex -> putamen ->GPi ->thalamus ->Cortex
Inhibition of GPi by putamen stops GPi from sending inhibitory output to thalamus

Front 56

Basal ganglia - INDIRECT PATHWAY

Back 56

INDIRECT PATHWAY—inhibition—suppresses movement
Cortex -> putamen -> GPe ->GPi ->Thalamus ->Cortex
STN
Cortex activation of STN activates GPi, combined with inhibition of GPe by putamen which stops GPe inhibition of GPi and the STN allows GPi to send its inhibitory output to the thalamus.

Front 57

Dopamine's role in basal ganglia pathways

Back 57

DOPAMINE From SNc (substantia nigra pars compacta), influences both pathways using D1 excitatory and D2 inhibitory receptors.
Therefore dopamine facilitates the direct pathway and inhibits the indirect pathway to permit movement to occur.

Front 58

3. What is the cellular circuitry within the basal ganglia and what is the functional significance?
Graphs of activity during monkey eye movement

Back 58

(1) Recorded activity in the head of the caudate when input from the frontal eye fields is received.
(2) Neurons in the substantia nigra pars reticulata maintain a steady tonic firing rate that inhibits the superior colliculus—the (3) superior colliculus is quiet when the substantia nigra is active.


However when the caudate receives excitatory input, it inhibits the substantia nigra pars reticulata which then ceases firing, leading to disinhibition of the superior colliculus—the eye muscles are then are activated and the eyes move (4) in the selected direction.

Front 59

4. What are the 3 categories of functional loops of the basal ganglia?

Back 59

A. Sensory/Motor
B. Cognitive: Executive/Behavioral
C. Limbic (emotional)

Front 60

4. What is the Sensory/motor functional loop of the basal ganglia?

Back 60

Scale movement amplitude and speed, generates internal cues for initiation of and building of sequential and simultaneous movements/actions, proprioceptive processing allows for online accurate self monitoring and correction of movement

Cortical regions sending input and receiving output:
Somatosensory cortex
Supplementary motor area
Premotor cortex
Primary motor cortex
Striatal Input regions:
Putamen

Information flows through the BG in distinct parallel circuits. Each circuit originates from functionally distinct regions of the cerebral cortex, passes through distinct regions of the basal ganglia (striatum and output nuclei) and thalamus, and return to modulate their functionally distinct cortical regions. The also BG have a strong connection to the brainstem nuclei as well for automatic control.

Front 61

4. What is the Cognitive: Executive/Behavioral functional loop of the basal ganglia?

Back 61

Goal selection, sequencing, preparation for movement, Attention to action and context for quick adaptation and selection of most effective response, working memory, perceptions of space/time

Cortical regions sending input and receiving output:
Lateral orbitofrontal
Posterior parietal cortex
Lateral prefrontal cortex
Striatal Input regions:
Caudate

Information flows through the BG in distinct parallel circuits. Each circuit originates from functionally distinct regions of the cerebral cortex, passes through distinct regions of the basal ganglia (striatum and output nuclei) and thalamus, and return to modulate their functionally distinct cortical regions. The BG also have a strong connection to the brainstem nuclei for automatic control.

Front 62

4. What is the limbic functional loop of the basal ganglia?

Back 62

Reward, habit formation, motivation, mood, vigor

Cortical regions sending input and receiving output:
Anterior cingulate
Medial orbitofrontal cortex
Striatal Input regions:
n. Accumbens/
Ventral striatum

Information flows through the BG in distinct parallel circuits. Each circuit originates from functionally distinct regions of the cerebral cortex, passes through distinct regions of the basal ganglia (striatum and output nuclei) and thalamus, and return to modulate their functionally distinct cortical regions. The BG also have a strong connection to the brainstem nuclei for automatic control.

Front 63

What are the 5 specific parallel BG loops within the 3 categories.

Back 63

There are 5 specific parallel BG loops within the 3 categories.

A. Sensory/Motor:
Voluntary motor
Oculomotor

B. Cognition:
Executive function—plan, choose
Behavioral flexibility—social appropriate

C. Limbic:
Emotional, mood—reward, motivation


This slide emphasizes the thalamo-cortical connection. See next slide for brainstem output concept.

Front 64

General outputs for the basal ganglia loops.

Back 64

Basal ganglia outputs to cortex and brainstem
Black arrows = inhibitory synapses
White arrows = excitatory synapses

VOLITIONAL CONTROL - Cortico-BG loop

BG-> Thalamocortical output functions:
Volitional movement
Cognition—executive function, social behavior
Emotion—mood, motivation

AUTOMATIC CONTROL - BG/BS system

BG -> Brainstem output functions:
Locomotion
Postural control
Muscle tone
Eye saccades
Automatic emotional responses/behaviors

Front 65

A. Sensory/Motor Behavior loops (1&2): Volitional and Automatic motor behaviors

Back 65

Volitional Loop 1:
In: Sensorimotor areas of cortex->putamen
Out: Gpi-VA/VL of thalamus->motor cortex
Auto Loop 2:
In: Sensorimotor areas of cortex or frontal eye fields->putamen/body of caudate->
Out: SNpr to brainstem locomotor region (MLR: midbrain locomotor region), postural region (PPN), or oculomotor (superior colliculus)
Cortical inputs and thalamic inputs and then outputs—lets basal ganglia link automatic movement sequences embedded throughout nervous system (brainstem, spinal cord) into volitional goals/behavioral salience/choice completion.
Links intentional act with automatic—selects/tunes automatic to fulfill volitional intent, so it is appropriate choice, useful to goals wanted by cortex.
Occulomotor Saccade: spontaneous & visually guided rapid eye movements directed towards contralateral visual field. permit scanning in specific direction. movement towards target in space. Inputs from frontal eye fields can output to superior colliculus & back to eye fields

Front 66

Note: The effect of the BG on the PPN is to have it be able to inhibit the

Back 66

Note: The effect of the BG on the PPN is to have it be able to inhibit the reticulospinal tracts which reduces the amount of muscle tone which permits movement to occur.

Front 67

Fill in whether the connections between each structure are excitatory or inhibitory

BG - motor thalamus - motor cortex - corticospinal tracts - LMNs - voluntary muscles

Back 67

BG - (inhibitory) - motor thalamus - (excitatory) - motor cortex - corticospinal tracts - LMNs - voluntary muscles

Basal Ganglia inhibit the motor thalamus, everything else is excitatory

Front 68

Fill in whether the connections between each structure are excitatory or inhibitory

BG - - Pedunculopontine nucleus VL -- Reticulospinal tracts -- LMNs - postural and girdle muscles

Back 68

BG -(inhibitory) - Pedunculopontine nucleus VL -inhibit- Reticulospinal tracts -excite- LMNs -excite- postural and girdle muscles

Front 69

Fill in whether the connections between each structure are excitatory or inhibitory

BG -- Midbrain locomotor region -- reticulospinal tracts -- stepping pattern generators -- LMNs -- walking

Back 69

BG -inhibit- Midbrain locomotor region -excite- reticulospinal tracts -excite- stepping pattern generators -excite- LMNs -excite- walking

Front 70

5 Functional Loops
Cognition loops (3&4):

Back 70

Cognition loops (3&4):
Association areas -> caudate-> VA or mediodorsal thalamus to prefrontal cortices

Examples:
Dorsolateral prefrontal circuit: Working memory, monitoring behaviors, organizing behavioral responses, verbal problem solving, Goal-directed behavior; makes perceptual decisions, plans, and decides upon actions in context
 
Lateral orbitofrontal circuit:—organizing empathetic and socially appropriate responses, Recognition of social disapproval, self-regulatory control, selecting relevant knowledge from irrelevant, maintaining attention, stimulus-response learning.

Front 71

5 Functional Loops
Mood/non motor behaviors (5):

Back 71

Mood/non motor behaviors (5):
Limbic areas -> n accumbens/ventral striatum -> mediodorsal thalamus to limbic cortices OR SNpr to brainstem automatic behavior centers for emotion, autonomic regulation
 
Emotional behavioral and motivated behavior regulate emotional behavior and motivation motivated behavior—reinforcing stimuli to multiple areas, involved in reward-guided behaviors; monitors errors in predictions; concerned with seeking pleasure

Front 72

5. What are the impairments and diagnoses associated with basal ganglia lesions/dysfunction? ?
Movement Disorders with non-motor symptoms—two ends of the spectrum: Hypokinesia

Back 72

Basal Ganglia Pathology—changes in movement, cognition, and mood/behavior that reflect an imbalance between direct and indirect pathways:

Movement Disorders with non-motor symptoms—two ends of the spectrum:


Hypokinesia - lack of movement Parkinson’s Disease characterized by:

Rigidity, apathy, flat affect, depression, delayed initation and termination of motor programs, lack of empathy, failure to respond to social cues

Front 73

5. What are the impairments and diagnoses associated with basal ganglia lesions/dysfunction? ?

Movement Disorders with non-motor symptoms—two ends of the spectrum:

Hyperkinesia

Back 73

Basal Ganglia Pathology—changes in movement, cognition, and mood/behavior that reflect an imbalance between direct and indirect pathways:

Movement Disorders with non-motor symptoms—two ends of the spectrum:

Hyperkinesia: too much movement Huntington’s Disease, hemiballismus - characterized by

Impulsivity, ballismus/chorea, involuntary motions/tics, outbursts, animation, OCD, Schizophrenia, mania, irritability, lability, premature/unintended activation of motor programs

Front 74

PARKINSON’S DISEASE - DOPAMINE from SNC ABSENT (see dotted arrows) - net effect is to

Back 74

PARKINSON’S DISEASE- DOPAMINE from SNC ABSENT (see dotted arrows)- net effect is to increase inhibitory output (see large red arrow)

Resting tremor in Parkinson's disease is associated with Rhythmic firing of neuron groups in the subthalamic nucleus.

Front 75

HUNTINGTON’S CHOREA: Degeneration of striatal neurons in the ___ pathway (see dotted red line) - net effect is _____________

Back 75

HUNTINGTON’S CHOREA: Degeneration of striatal neurons in the indirect pathway (see dotted red line) - net effect is unfocused direct pathway output.

Front 76

Note: the rigidity see in PD is due to

Back 76

Note: the rigidity see in PD is due to lack of inhibition of the PPN—this means the PPN is unable to inhibit the descending reticulospinal tracts. This means that the reticulospinal tracts will continue to activate all muscles thus increasing muscle tone causing rigidity. Increased inhibition of the PPN, disinhibits the reticulospinal tracts, producing excessive contraction of postural muscles—rigidity.

Front 77

The difficulty in Parkinson's with inititating and changing automatic movements like gait is due to

Back 77

The difficulty with inititating and changing automatic movements like gait is due to lack of inhibition of the MLR—this means that the MLR (much like the thalamus) is unable to activate the reticulospinal tracts, thus causing lack of gait, festination and freezing.

Front 78

Huntington's disease is characterized by ____ of the _____ by the ___ leading to chronic _____ of the thalamus and the pedunculopontine nucleus. This is due to degeneration of the _____ neurons.

This results in

Back 78

Huntington's disease is characterized by excessive direct pathway inhibition of the globus pallidus internus by the putamen leading to chronic disinhibition of the thalamus and the pedunculopontine nucleus. This is due to degeneration of the striatal indirect pathway neurons.

This results in excessive activity of the motor areas of the cerebral cortex by the thalamus, producing hyperkinesias, combined with excessive output from the pedunculopontine nucleus, causing insufficient activity in reticulospinal tracts inhibit the postural muscles. The midbrain locomotor region is omitted from this figure because no data are available on its function in Huntington's disease. Subthalamic nucleus output to inhibit the Gpi is decreased due to enhanced inhibition by globus pallidus externus (not shown).

Front 79

Clinical Diagnosis of PD based on motor symptoms

Back 79

Early Motor Symptoms: Need 2/3 for DX
Bradykinesia, Tremor, Rigidity
Insidious onset
Nonmotor and early motor symptoms
Asymmetrical distribution

Differential DX -No blood testing will show PD

Front 80

S/S at time of diagnosis of PD

Back 80

Time of Diagnosis
Bradykinesia
Gait hypokinesia
Resting tremor
Micrographia
Hypophonia
Stooped posture
Decreased dexterity
Masked Face
Rigidity

Front 81

S/S at time of referral to PT (usually)

Back 81

Time of Referral to PT:
Generalized hypokinesia
Akinesia (go problem- start hesitation)
Festination (no-go impairment)
“Freezing”episodes (no-go/go impairment)
Postural instability
Swallowing
Adaptive responses (e.g., weakness, contractures, decreased aerobic capacity

Related to inadequate scaling of motor output
Related to inadequate timing signals
Multifactorial

Front 82

PD Non-motor Symptoms

Back 82

Anxiety */ Depression:
25% major/17% minor
precedes motor symptoms
may contribute to dementia

Loss of higher cognitive functions:
Shifting cognitive set
Slow thinking
Retrieval
Self-cueing
Sustaining attention

Dementia:
30%-65%
occurs 6.6X as frequently than in elderly non-PD
shortens survival

Autonomic abnormalities:
hypotension, bowel * / bladder, sexual, blurry vision, short of breath

Sensory changes:
pain, tingling, burning *
Generalized decreased kinesthetic proprioceptive awareness
-Self-perception/monitoring
-Loss of smell *
Sleep Disorders*

*= signs prior to motor signs…lead to earlier diagnosis

Front 83

Hoehn and Yahr Scale for classifying staging severity of PD motor signs
(Hoehn and Yahr, 1967; Goetz et al, 2004)

Back 83

Stage 0: No signs of disease.
Stage 1: Unilateral symptoms only.
Stage 1.5: Unilateral and axial involvement.
Stage 2: Bilateral symptoms. No impairment of balance.
Stage 2.5: Mild bilateral disease with recovery on pull test. *
Stage 3: Balance impairment. Mild to moderate disease. Physically independent.
Stage 4: Severe disability, but still able to walk or stand unassisted.
Stage 5: Needing a wheelchair or bedridden unless assisted.

*Recovery is defined as "the patient recovers by himself and needs a maximum of two steps.“

Front 84

I. PRINCIPLES OF SYSTEMS NEUROSCIENCE:

Defining a system:

Back 84

I. PRINCIPLES OF SYSTEMS NEUROSCIENCE:

Defining a system: numerous interconnected structures throughout the brain and spinal cord that form synaptic relays between each other so that information travels between structures, through the system.

A system, anatomically, is comprised of both structures and pathways between the structures.
Structures are found in different levels or regions of the nervous system. The levels are labeled SUPRASPINAL—which is divided into CORTICAL and SUBCORTICAL—and SPINAL.

Pathways then connect the different levels to each other. Pathways also the different structures within a level.

Front 85

Analogy for the cortex as the “top” of the hierarchy: Cortex is the

Back 85

Analogy for the cortex as the “top” of the hierarchy: Cortex is the piano player—the subcortical regions are the piano. We all have the same keys/instrument  what makes us different is the experience of the player. The piano player can’t play without a piano—the cortex can’t perceive nor produce movement without the rest of the regions of the nervous system that are distributed from the periphery to the spinal cord, brainstem, and subcortical structures all the way up to the cortex. Each level as the instrument has certain innate capacity for sensation, movement, and learning/modification—experience dependent plasticity

Front 86

For motor system: cortex offers

For sensory system: cortex offers

Back 86

For motor systemcortex offers combination/complexity/control of volitional movements that the lower levels (brainstem, spinal cord) will implement (kind of like a leader for the troops but the cortex can’t do what the troops do).

For sensory systemcortex offers new dimensions of conscious analysis of sensory events and capacity. For example you all are gaining sensory skills in visual observation of movement dysfunction as well as somatosensory skills in palpation. Also the somatosensory feeling that can be recognized as “empty end feel” during passive motion of patient’s shoulder.

Front 87

HIERARCHY WITHIN SYSTEMS IN THE CORTEX

Back 87

HIERARCHY WITHIN SYSTEMS IN THE CORTEX—cortical processing across three adjacent regions with each one integrating information from the one before. PrimarySecondaryTeritiary Cortices
SEQUENTIAL or SERIAL PROCESSING figure A

Example: Motor—prefrontal association area (tertiary)  premotor cortex (secondary)  primary motor cortex (Primary)

Somatosensory processing in the parietal lobe from S1 (area 3,1,2)  PPC (Area 5,7)  an association cortex.

Front 88

DISTRIBUTED AND PARALLEL PROCESSING WITHIN AND BETWEEN SYSTEMS IN THE CORTEX—

Back 88

DISTRIBUTED AND PARALLEL PROCESSING WITHIN AND BETWEEN SYSTEMS IN THE CORTEX—what we know now to be true—one piece of information can be processed within its level and within its system but it can also be shared with other systems then to higher levels and even skip a level PARALLEL & SERIAL PROCESSING figure B

Example: integration of somatosensation and vision in the parietal lobe (Area 5,7). Distribution of pain information to the sensory cortex, the limbic cortex, and the brainstem.

Front 89

Functions of the posterior and anterior regions of the cortex

Back 89

The posterior regions (Parietal, Occipital, and Temporal lobes) understand the world as they receive sensory inputs and the anterior regions (Frontal Lobe) allow us to respond and to move around in that world and manipulate it to meet our needs/solve problems.

The cortex gives us the ability to make conscious, volitional choices about how to move and it gives us the ability to initiate specific actions to meet our needs.

Front 90

3. Somatotopic organization in systems—structures and pathways: Example using the Motor System

Back 90

Somatotopic map of the Primary motor cortex (top) reflects the density of connections between the brain and spinal cord motor pools. Therefore the size of the brain map is not the same as the anatomical size of the body.

(Right) This is what we might look like if the motor cortex got to make us—cute little human with ENORMOUS HANDS and MOUTHS. ??With such
wimpy little arms, how could we hold up our BIG hands??
The somatotopic map of the ventral horn (bottom)—this figure takes the cervical enlargement and squishes it down into one location to show the distribution of the motor pools between C4-T1
The pathway that will connect the motor cortex (cell body for the tract) to the motor pools (axon terminals for the tract) in the spinal cord will also have a somatotopic arrangement as it travels through the internal capsule in the subcortical region of the brain (left).

And then as the lateral corticospinal tract in the spinal cord (below).

Front 91

Motor System: supraspinal structures and descending pathways

Back 91

SUPRASPINAL STRUCTURES
CORTICAL- M1, PMA, SMA, broca’s, mirror neurons, opposite broca’s, cingulate motor area
SUBCORTICAL-Basal Ganglia, Cerebellum, Thalamus,
Brainstem Nucleii—Reticular Formation (PPN, MLR), M&L Vestibular Nucleii, Red Nucleus, Superior colliculus

DESCENDING PATHWAYS:
CORTICAL- Lateral CST, Anterior CST
SUBCORTICAL- LRST, MRST, RubroST, MVST, LVST, TST

Front 92

Motor System: SPINAL& BRAINSTEM LOCAL CIRCUITS AND EFFECTOR STRUCTURES

Back 92

(Spinal & Cranial nerves)
INTERNEURONS -local interneurons , propriospinal pathways for Synergies, CPGS, Automatic Reactions/Responses, Reflex loops
GAMMA motor neurons,
SENSORY neurons/axons
ALPHA Motor Neurons (lower motor neurons—final common pathway),

Front 93

5 CATEGORIES OF MOTOR ACTIONS:

Back 93

Reflex:

Synergy:

Stereotypical rhythmic, repetitive patterns or sequential patterns:

Stereotypical automatic reactions/responses:

Voluntary/volitional movements:

Front 94

5 CATEGORIES OF MOTOR ACTIONS: Reflex

Back 94

stereotypical and fast motor response to a specific sensory stimulus. The response is graded to the intensity of the stimulus—stronger stimulus, stronger response. The response can habituate—become less strong with repetitive exposure to the same stimulus.

Front 95

5 CATEGORIES OF MOTOR ACTIONS: Synergies

Back 95

Synergy: Neuronal circuit between interneurons and motorneurons from different muscles that produce a set of muscle activations that have the timing and amount of force needed to produce specific kinematic events. (see next slide). These synergies are recruited by descending inputs—as opposed to individual alpha motor neurons themselves. Synergies serve as the building blocks of movement/that which are recruited by descending pathways, CPGS, automatic responses, reflexes

Front 96

5 CATEGORIES OF MOTOR ACTIONS: Stereotypical rhythmic, repetitive patterns or sequential patterns:

Back 96

Stereotypical rhythmic, repetitive patterns or sequential patterns: Neuronal circuits that produce coordinated motor patterns across multiple segments of the spinal cord. Network of neurons that automatically generates an alternating, rhythmic pattern of activity. A CPG may recruit synergies. Examples include breathing, walking, chewing, swallowing. Turned “on” by descending inputs and maintained/modulated by incoming sensory afference.

Front 97

5 CATEGORIES OF MOTOR ACTIONS: Stereotypical automatic reactions/responses:

Back 97

Stereotypical automatic reactions/responses: Stereotypical patterns of movement across segments—recruited by descending brainstem pathways for automatic response like balance reactions, startle response, or triggered reactions for maintaining grip with something slips.

Front 98

5 CATEGORIES OF MOTOR ACTIONS: Voluntary/volitional movements:

Back 98

Voluntary/volitional movements: intention movement to accomplish a goal. Will incorporate all of the other categories of motor actions as they are performed.
Classes: Postural Control, Locomotion, Reach/Grasp/Manipulation
Phases: Before, During, After

Front 99

Category 2: Synergies are groups of motor neurons (from different muscles) that are activated as a unit by _______. the synergy module not only says which muscles will be used but also _____.

The synergy interneurons specify:
1)
2)

Back 99

Category 2: Synergies are groups of motor neurons (from different muscles) that are activated as a unit by an interneuron. the synergy module not only says which muscles will be used but also how much of a muscle will be used and when will it be used.

The synergy interneurons specify:
1)Amount of force for each individual muscle. The interneuron activates enough motor neurons in each muscle to produce a certain amount of force (see the bar graphs on the left: Red synergy has 3 muscles each activated a different amount, Green synergy has 2 muscles.
2) Timing for the amount of forces. The interneuron also determines the timing of the combined muscle activation (see the wave forms under the bar graphs).

The synergy interneuron activates the group to produce a certain force level (height of the arc) for a certain period of time (width of the arc) at different points in time during the motion (time point along the line).

Front 100

Therefore, different movements are due to a combination of synergies recruited by _____. The _____recruits the synergies or modules that together make the movement happen.
An analogy: if the muscles are the letters of the alphabet, synergies put the ____together to make ____. The brain figures out _____ where as the synergies/modules take the letters (which are the different ___) and make _____.

The current thought in motor control is that Brain is not trying to activate ____. It’s trying to activate a _____ to translate a goal into an action. The modules are recruited in a task specific way

Back 100

Thereforedifferent movements are due to a combination of synergies recruited by descending inputs. The descending info recruits the synergies or modules that together make the movement happen.
An analogy: if the muscles are the letters of the alphabet, synergies put the letters together to make words. The brain figures out sentences where as the synergeis/modules take the letters (which are the different muscles) and make words.

The current thought in motor control is that Brain is not trying to activate particular muscle. It’s trying to activate a particular motion to translate a goal into an action. The modules are recruited in a task specific way

Front 101

Movements are generated by dedicated networks of nerve cells that contain the information necessary to activate different motor neurons in the appropriate sequence and intensity to generate motor patterns. Such networks are referred to as

Back 101

Movements are generated by dedicated networks of nerve cells that contain the information necessary to activate different motor neurons in the appropriate sequence and intensity to generate motor patterns. Such networks are referred to as

Central pattern generators (CPGs)
Most basic CPGs coordinate protective reflexes, swallowing or coughing. Next level generate rhythmic movements. Respiratory CPGs are active throughout life but modulated with changing metabolic demands. Locomotor CPGs are inactive at rest, but turned on by signals from command centers.

Front 102

Category 4 Stereotypical Automatic responses or reactions: multisegmental (across the body) organized responses to ___ input for feedback based ____ and/or incorporated into ____ motion

Back 102

Category 4 Stereotypical Automatic responses or reactions: multisegmental (across the body) organized responses to sensory input for feedback based corrections and/or incorporated into volitional motion (automatic postural responses to orient eyes to horizon).

These responses save the movement--are tuned to achieve the goal of the movement. Example for balance--don’t fall down.
Also tuned to the context of the movement--won’t use an ankle strategy when standing on a balance beam. Instead you’ll use a hip strategy.

Front 103

MOTOR SYSTEMS/ ACTION SYSTEMS AND THE PHASES OF VOLITIONAL MOVEMENT overview of steps involved:

Back 103

MOTOR SYSTEMS/ ACTION SYSTEMS AND THE PHASES OF VOLITIONAL MOVEMENT overview of steps involved:
BEFORE you see the volitional movement appear/EMG in the muslce
Choose to move
Plan the movement
Send the plan via the tracts to the effectors in the spinal cord

DURING—motor execution. Recruit the spinal cord circuits and alpha/lower motor neurons
Motor units fire to execute the motion by muscle contractions
Error correction/monitor performanc

AFTER (not shown) Record/Learn to adjust and improve the next motion. Activity dependent synaptic changes.

Front 104

Where are different CPGs located?

Back 104

Spinal cord: locomotion and protective reflexes
Brainstem: breathing, chewing, swallowing, saccadic eye movments
Hypothalamus: eating and drinking areas that coordinate activation of different CPGs in a behaviorally relevant order. Fluid intake area - animal looks for water, walks towards it, positions itself, and starts drinking

Front 105

Synergies During movement execution

Back 105

Motor execution: interneurons that coordinate a combination of muscles in one limb, in the trunk, into a pattern of movement. These synergies are recruited by descending inputs rather than individual muscles themselves. Activations of muscles in space and time serve as the building blocks of movement/that which are recruited by descending pathways, CPGS, networks, reflexes

Front 106

CPGs During movement execution

Back 106

Network of neurons that automatically generates an alternating, rhythmic pattern of activity—can recruit synergies to alternate activity. Turned “on” by descending inputs and maintained/modulated by incoming sensory afference

Front 107

Reflexes DURING movement execution

Back 107

Involuntary motor acts elicted by incoming sensory stimuli.—cutaneous, muscle. Local responses—one sensory stimulus elicits a responses. Can be modulated/tuned by descending inputs. For example gamma biasing.

Front 108

Interneuronal networks for automatic responses DURING movement execution

Back 108

Stereotypical patterns of movement across segments—recruited by descending brainstem pathways for automatic response, triggered reactions, sequences of motions.

Front 109

Ventral horn: alpha motor neurons and gamma motor neurons DURING movement execution

Back 109

Organized with medial neurons projecting to axial limb and trunk muscles, lateral neuron pools project to distal limb muscles.

Gamma motor neurons to muscle spindle for muscle spindle sensitivity for movement feedback

Front 110

Sensory afferents DURING movement execution

Back 110

While not a motor structure, sensory afferents will influence motor output and can be modulated by presynatpic inputs from descdenidng pathways and interneours

Front 111

The key issue with the spinal cord:

Back 111

The key issue with the spinal cord: it has the capacity to select muscles to be used to accomplish the goal specified in the descending input . Sensory afference will modulate responses such that repeated exposure will lead to spinal cord learning/circuitry adaptations—the basis for treadmill training.

Front 112

The Spinal Cord is “smart” and can learn:
Muscle synergies—electrical activity in neurons recorded during frog swimming-

Back 112

The Spinal Cord is “smart” and can learn:
Muscle synergies—electrical activity in neurons recorded during frog swimming- muscle pattern is consistent and will change when a obstacle is present.

Experiment 2: RECORD SYNERGY BEHAVIOR IN ACTIVE ANIMAL:
Record EMG under both conditions—with and without an obstacle
Only hip flexors (SA, GR, RA) change activity in presence of obstacle—in order to clear the obstacle. The synergy can respond to sensory input.
CNS specifies movement which is created by the spinal cord sequences and linear summations of motor modules.
These modules/synergies can be used by reflex loops, CPGs, and automatic reactions.

Front 113

Associated motor functions of: M1,Brodman 4, precentral gyrus

Back 113

Motor planning & execution: Fine dexterity/precise postures of distal muscle groups—hand, face. Force code for direction of joint motion. Single joint motions. Home of the official motor homonculous.
Inputs from Premotor cortex, cingulate motor cortex, BG and CB via the thalamus

Motor execution: Origin for corticospinal and corticobulbar tracts

Front 114

Associated motor functions of:
PreMotor Area
Brodman 6
Middle frontal gyrus

Back 114

Motor planning: External driven—UE/head/neck postures, learning new motions, Anticipatory postures for proximal stability/distal mobility, Multi joint motions bringing target to body.
Inputs from sensory cortex and cerebrocerebllum

Motor execution: Origin for corticospinal and corticobulbar tracts

Front 115

Associated motor functions of:
Supple-mentary Motor Area
Brodman 6
Superior frontal gyrus

Back 115

Motor Planning: Internal driven—trunk/LE postures, bimanual, sequences, well learned. Movement initiation , Complex internal drive motions.
Inputs from BG

Motor execution: origin for corticospinal and corticobulbar tracts.

Front 116

Associated motor functions of:
Cingulate Motor Area
Brodman 23/24 Cingulate Gyrus

Back 116

Emotional/internal motivational aspect of motor planning—provides info to drive what need to meet
Inputs from limbic cortex
Output to corticospinal tract and M1

Front 117

Key Issue with the motor homonculous and the motor cortex: Based on the work by Graziano, the role of the motor cortex seems to be

Back 117

Key Issue with the motor homonculous and the motor cortex: Based on the work by Graziano, the role of the motor cortex seems to be selecting the combinations of movements that will achieve the intended volitional movement goal—get the food to your mouth—as opposed to specifying the particular muscles/muscle groups that will achieve the goal. It specifies the movements that will solve what Bernstein called the movement problem—control and intention of movements that can be elicited at brainstem and spinal cord levels.

Front 118

Associated motor functions of:
Broca’s Area Dominant side &
Non dominant side
Brodman 44,45
Inferior frontal gyrus

Back 118

Motor planning & execution: oral motor plan for facial, mouth and throat muscles for speech production (dominant side), facial control for nonverbal communication (non-dominant side)

Motor execution: Origin for corticobulbar tracts to cranial nerves

Front 119

Associated motor functions of:
Frontal eye fields
Brodman 8

Back 119

Motor planning and execution of volitional eye movements.

Motor execution: Origin for corticobulbar tracts

Front 120

Associated motor functions of:
Mirror Neuron Action system
Brodman 40, 44
Frontal operculum & Inteferior parietal lobule Supramarginal gyrus

Back 120

Motor Planning: Action observation—

Motor execution: motor imitation of goal directed movement with objects, with speech, with full body movements.

Front 121

DOES THE CORTEX CONTROL MUSCLES OR MOVEMENT?

Back 121

Stimulation of a single site for a ½ second specified a final posture for the upper extremity and the mouth, regardless of starting position for the upper extremity.

(pictures of monkey with different paths traced to his mouth)

Front 122

Key Points from:
Graziano, The Cortical Control of Movement Revisited Neuron 36:349-362, 2002
Scheiber Constraints on Somatotopic Organization in the Primary Motor Cortex Journal of Neurophysiology 86:2125-2143, 2001.

Back 122

Key Points:

Stimulation of the motor cortex (M1PMC) with .5sec duration stimulation trains evokes complex multijoint postures that are behaviorally significant/functionally relevant.
The motions observed take the animal’s limb from any starting position in space to a consistent final position.
There is a gradient of postures across the cortex with more precise hand grips and facial expressions located in M1 (consistent with the framework of the motor homonculous) and upper extremity reaching with grasp in the PMA region (consistent with external driven motions) and trunk lower extremity motions in the SMA region (consistent with internally driven motions). See next slides.

Front 123

Strict somatotopic organization of M1 would predict that the territory active during movements of multiple fingers should be larger than that during movement of a single digit. When this has been tested, however,

Back 123

Strict somatotopic organization of M1 would predict that the territory active during movements of multiple fingers should be larger than that during movement of a single digit. When this has been tested, however, the extent and amplitude of activation in the primary sensorimotor cortex as been significantly larger during movement of a single finger than during simultaneous movement of multiple fingers. Such results indicate that the process of moving multiple isn't simply the sum of activating multiple separate M1 territories (for each finger); rather, moving 1 finger w/o others requires more M1 activity. Presumably, such extra activation occurs because, besides controlling motion of one finger, M1 actively participates in stabilizing other parts of the upper extremity during the individuated movement of a particular finger.

Front 124

The brainstem has four motor centers that send efferent fibers to the spinal cord:
These motor centers give rise to the:

Back 124

red nucleus (midbrain), lateral vestibular nucleus, tectum, and reticular formation

rubrospinal, vestibulospinal, tectospinal, and reticulospinal tracts
pathways under control of sensorimotor cortex and cerebellum

Front 125

Associated motor functions of vestibular nuclei

Back 125

Automatic reactions/postural,
gaze stabilization/smooth pursuit, vestbular ocular reflex (VOR), vestbiulospinal reflex (VSR)

Motor execution: Origin vestibular spinal tracts—medial and lateral, Origin of MLF for eye muscle coordination

Front 126

Associated motor functions of reticular formation

Back 126

Postural tone, pain modulation, arousal, breathing, chewing, swallowing, gait onset, descending autonomic regulation between PNS/SNS activation i.e. cardiac, bowel/bladder sphincter control, emotional expressions

Motor execution: Origin for reticulospinal tracts—medial and lateral

Front 127

Associated motor functions of red nucleus

Back 127

Distal limb motions/augment other lateral descending pathways especially LCST
Output nucleus for cerebellum and circuit with the olive

Motor execution: origin for Rubrospinal tract

Front 128

Associated motor functions of cranial nerves

Back 128

Facial muscles, oral/motor, eye movements execution by synapse from Corticobullbar tract
Cranial nerve reflexes

Front 129

Associated motor functions of superior colliculus

Back 129

Orient head/neck to visual/auditory/pain stimuli, visual saccades
(Sheldon!)
Motor execution: origin for tectospinal tract

Front 130

The key issue with the brainstem:

Back 130

The key issue with the brainstem: it has the networks that control most mobility motions—postural support, automatic responses, sequential behaviors, gait, emotional reactions/facial expressions, breathing, chewing, swallowing necessary for survival, fight/flight reactions—etc. These motor regions can function with sensory input and subcortical drive from the cerebellum and/or brainstem independent from the cortex. They can also be recruited by the cortex during volitional movement.

Front 131

BG -> THALAMOCORTICAL OUTPUT FUNCTIONS:

BG ->THALAMOCORTICAL OUTPUT FUNCTIONS:

Back 131

BGTHALAMOCORTICAL OUTPUT FUNCTIONS: VOLITIONAL CONTROL

VOLITIONAL MOVEMENT
COGNITION
EMOTION

BGBRAINSTEM OUTPUT FUNCTIONS: AUTOMATIC CONTROL

LOCOMOTION
POSTURAL CONTROL
MUSCLE TONE
EYE SACCADES

Front 132

GENERAL FUNCTION OF THE BASAL GANGLIA:

Back 132

Main functions:
Facilitate the automatic execution of selected sequential motor programs while simultaneously suppressing all other potentially competing and interfering motor programs.
Regulate initiation and termination of motor sequences, cognitive processes, emotional responses/reactions.
Interrupt behavior to favor/permit a response to a novel/behaviorally significant stimulus.
Scale amplitude/duration/force of postures and movements during the execution of a motor plan.

Front 133

The basal ganglia function together as a

Back 133

filter—the striatum gathers a variety of info from several different regions in the cortex and detect specific patterns of activity that warrants a response such as movement sequence, attention, emotion, cognitive process. The goal is to permit the right response to occur.

The direct pathway functions as a pause button on the otherwise tonic inhibition to thalamus and SNr from Gpi to allow the initiation of selected motor programs.

The indirect pathway enhances the inhibiton of unwanted motor programs or even stops/interrupts ongoing motor programs to allow a new program wanted by the direct pathway.

Front 134

Motor Behavior: Volitional and Automatic behaviors
Role of basal ganglia

Back 134

Motor Behavior: Volitional and Automatic behaviors
Sensorimotor areas -> putamen -> thalamus to motor cortex OR SNpr to brainstem locomotor region (MLR), postural region (PPN), or oculomotor (superior colliculus)

Cortical inputs and thalamic inputs and then outuputs—gives basal ganglia ability to link automatic movement sequences embedded throughout the nervous system (brainstem, spinal cord) into volitional goals/behavioral salience/choice completion. Links the intentional act to with the automatic—selects/tunes the automatic to fulfill volitional intent, so it is appropriate choice, useful to goals wanted by cortex.

Example of automatic behavior: Occulomotor Saccade: spontaneous and visually guided rapid eye movements directed towards the contralateral visual field. To permit scanning in a specific direction. Get movement towards a target in space. Inputs from frontal eye fields

Front 135

CEREBELLUM: Overview:

Back 135

CEREBELLUM: Overview:
10% of the brain volume—yet contains >50% of the neurons in the brain.
Involved in all three phases of volitional movement—plan, execute, record.
Participates in all classes of volitional movement—skilled reach/grasp, locomotion, and balance postural control.
Also involved in non movement functions: cognition/executive functions, language, emotion/affective function, and visual-spatial processing.
General output is excitatory to thalamic and brainstem targets. (compare to the Basal Ganglia which is inhibitory).

Front 136

General function of the cerebellum

Back 136

General function: Guardian angel role—watching over your every move in case you make a mistake or lose your balance. May implement a correction at that time but more importantly, makes sure the next move is better than the first.
Predictive feedforward control to help you to adapt to any situation/context.
You end up making less (fewer!) mistakes the next time.

Front 137

Role of cerebellum vs. basal ganglia in motor planning

Back 137

Motor Planning

Cerebro-Cerebellumtiming of joint actions within a movement. Details/Little picture of movement.

Basal Gangliatiming of movement sequences—select, initiate, terminate movements, in sequence. Big picture of movements

Front 138

Role of cerebellum vs. basal ganglia in Motor Learning

Back 138

Motor Learning

Spino-Cerebellumadjust the next movement in response to error signal from current movement. Adapts the next motion to different contextual demands. Receives corollary discharge. Learns by error. “Nope, try again.”
Adaptation learning—adapts a known skill to a new context.

Basal Gangliachoose the right movement to do based upon the reward received after the successful movement. Predict which movements will be successful by “reading” the sensory inputs that precede the reward. Learn by success. “A ha! That worked! Do it again!”
Motor skill learning—puts together new movements in to a new skill

Front 139

Extrapyramidal (indirect) and Pyramidal(direct) Systems:

Back 139

Extrapyramidal (indirect) and Pyramidal(dired) Systems: terms that refer to signs/symptoms. Corticospinal tract system damage that causes paralysis/paresis. Extrapyramidall—coming from Basal Ganglia and Cerebellar damage that cause problems with movement performance BUT DO NOT cause paresis.

Both systems are involved in all volitional movement.

Front 140

DESCENDING PATHWAYS
MEDIAL DESCENDING SYSTEM 5 Tracts

Back 140

DESCENDING PATHWAYS
MEDIAL DESCENDING SYSTEM 5 Tracts
1 from cortex: ASCT
4 from brainstem: LVST, MVST, MRST, TST
Proximal muscle groups
Synapse on spinal interneuron synergies, automatic reactions, CPG’s and usually bilaterally.

Front 141

LATERAL DESCENDING SYSTEM 3 Tracts to body and 1 Tract to the cranial nerves (see next slide)

Back 141

LATERAL DESCENDING SYSTEM 3 Tracts to body and 1 Tract to the cranial nerves (see next slide)
1 from cortex: LSCT
2 from brainstem: RST, LRST
Distal limb motion:
Synapse directly on alpha motor neurons as well as spinal interneuron synergies, CPG’s and usually unilaterally.
RST also specific to motor correction via cerebellar outputs.

Front 142

LATERAL DESCENDING SYSTEM
1 Tract to the cranial nerves

Back 142

LATERAL DESCENDING SYSTEM
1 Tract to the cranial nerves

CORTICOBULBAR TRACT

Synapse on cranial nerve motor nuclei—analogous to the corticospinal tract.

Also synapse on the brainstem nuclei that are the origin for the brainstem tracts.

And pontine nuclei—to go into the cerebellum.

Front 143

Descending Cortico-spinal and Corticobulbar Projection fibers: To spinal cord and cranial nerves—CorticoSpinalTract/CorticoBulbarTract—

Pathway:

Back 143

Descending Cortico-spinal and Corticobulbar Projection fibers: To spinal cord and cranial nerves—CorticoSpinalTract/CorticoBulbarTract—

Pathway: 1. corona radiata2. internal capsule3. cerebral peduncles4. Basis pons5. medullary pyramids where 90% of the fibers crosslateral funiculus of spinal cord
Remaining 10% don’t crossanterior/medial funiculus

Front 144

Origin of the Corticospinal tract: Layer 5 of

Back 144

Origin of the Corticospinal tract: Layer 5 of
50% from the M1 (homoculous above)
30% from Premotor Cortex (area 6)
20% from the Sensory Cortex in parietal lobe (areas 3,1,2 and 5,7).

Front 145

If Motor Control and Motor Execution is distributed across all of the descending pathways, what does the corticospinal tract do for us? Why is injury to this pathway so devastating to volitional movement—dexterity and strength?

Back 145

slide 59?

Front 146

Slide 60

Back 146

what does it mean?

Front 147

MOTOR UNITS=

Back 147

MOTOR UNITS= Motorneurons and Muscle Fibers they innervate.

A motorneuron will only innervate one muscle.

A muscle fiber is innervated by only one motorneuron.

A whole muscle has a designated pool of motorneurons that innervate it (see next slide).

The whole muscle is comprised of several motorunits that vary in size—and therefore the amount of force that they can produce.

Total amount of force—strength—neural determinants include number of motor units recruited and their discharge rates.

Muscle determinants include size of the muscle (a.k.a. the amount of contractile protein), the orientation of the muscle fibers, & length/tension relationship.

Front 148

Motorneuron characteristics: alpha motorneurons come in sizes

Back 148

Motorneuron characteristics: alpha motorneurons come in sizes

Small—recruited first because have HIGH resistance at the cell body (see next slide) but because they have an axon with a small diameter, they are slow for propagating the action potential down the axon.
Medium
Large—recruited last because they have low resistance at the cell body but they are fast propogators down the axon because they have a big diameter.

Front 149

Muscle fiber characteristics:

Back 149

Muscle fiber characteristics:

Metabolic profile—enzymes and mitochondria content that supports oxidative or glycolytic energry metabolism.

Oxidative—fatigue resistant, Increases in all fibers with increased use
Glycolytic—fatigue quickly, increases in all fibers with decreased use

2. Type of contractile proteins—myosin heavy chain subtypes based upon the speed of contraction that the actin/myosin bonds can make and therefore how fast the sarcomere can shorten.

Myosin atpase I—slow twitch, in small motor units, the first to be recruited
Myosin atpase Iia—fast twitch, in medium to large motor units
Myosin atpase IIb (or IIx)—fast twitch, in large motor units, last to be recruited

Metabolic characteristics can change independently from the contractile proteins—increased use increases oxidative capacity of all fiber types. Strength training (high load) increases the amount of type II myosin fast, endurance training (low load) increases the amount of type I myosin slow—becaus

Front 150

Motor units found in a muscle: a spectrum, not “two piles of I and II” or of “small and big” motor units.

Back 150

Motor units found in a muscle: a spectrum, not “two piles of I and II” or of “small and big” motor units.

Figure a: x axis is the number of motorneurons going to one muscle (the size of the motor pool) y axis indicates how many muscle fibers are innervated by each motorneuron. So motorneuron #120 innervates 1800 muscle fibers. Motorneurons 1-20 innervate less than 25 muscle fibers.

Figure b: x-axis is the number of motorneurons going to one muscle.
y-axis A Muscle will have all types of fibers in it—on a cross section, about 45% will have more Type I myosin atpase characteristics and about 40% wlll have more Type IIa myosin characteristics, and about 5% Type Iib (or IIx)

Therefore, motorneurons 1 to 105 innervate 45% of the muscle fibers. In other words 85% of the motorpool innervates 45% of the muscle—smaller motor units. 105 to 118 innervates 40% of the muscle—larger motor units. 118-120 innervates 5% really big motor units.

Front 151

Motor Unit recruitment threshold and order of recruitment

Back 151

Each muscle has a dedicated motor pool—those motorneurons project to only one muscle.

Example: Motor Pools for muscles innervated by the C5 and C6 nerve roots.

The motorneurons—and therefore the motor units are recruited in order of size—smallest to largest. This is known as the Henneman size principle (1957).


“MU recruitment threshold”: force at which the motorunit is recruited during a ramped contraction. This threshold varies with the speed and type of contraction. ( See next slide.)

Why do the small guys get recruited first? Small motorneurons have high resistance. They get recruited at low forces when the amount of synaptic input current/drive is small.

V=IR V: depolarization voltage (mV) I: amount of current (mAmps)
R: amount of resistance (ohms)

High resistance x Small current = Depolarization voltage that triggers an action potential.
Low forces have small synaptic currents—can’t recruit the big guys until you get enough current because the big guys have

Front 152

During isometric contractions: As force increases,

Back 152

more motor units are recruited and each motor unit increases its firing rate.

Front 153

TASK SPECIFICITY OF MOTOR UNIT RECRUITMENT and DISCHARGE RATES TO INCREASE FORCE OUTPUT—DIFFERENCE IN MOTOR UNIT BEHAVIOR BY CONTRACTION TYPE

Back 153

TASK SPECIFICITY OF MOTOR UNIT RECRUITMENT and DISCHARGE RATES TO INCREASE FORCE OUTPUT—DIFFERENCE IN MOTOR UNIT BEHAVIOR BY CONTRACTION TYPE
All contractions follow the size principles (only a few studies have found evidence that contradicts the size principles, the majority of studies confirm the size principle)

ISOMETRIC: Increase number of motor units recruited to increase force and also increase the discharge rates of those motor units that are already active.

CONCENTRIC: Increase number of motor units recruited—force recruitment thresholds measured during an isometric contraction are lowered during a concentric contraction (i.e. motor unit typically recruited at 20# of force in an isometric is now recruited at 15# of force in a concentric contraction) Discharge rates are more constant/unchanging. Therefore, activates as much muscle as possilble in a concentric contraction.

ECCENTRICS: Some evidence of de-recruitment of motor units as well as slowed discharge rates

Front 154

Distribution of synaptic input to the motorneuron pool differs across contraction types such that activation of the motor pool is task specific—

Back 154

Distribution of synaptic input to the motorneuron pool differs across contraction types such that activation of the motor pool is task specific—the recruitment threshold and discharge firing rates that comprise the forces needed for task performance vary even though the action may look exactly the same to the external observer.

Front 155

Changes in motor unit behavior with training.

Back 155

slide 69

Front 156

What are the general functions of the ANS?

Back 156

What are the general functions of the ANS?

HOMEOSTASIS—

AUTONOMIC MOTOR SYSTEM innervates smooth muscle, cardiac muscle, and glands.

MOTIVATE BEHAVIORS/ACTIONS TO MEET SYSTEMIC HOMEOSTASIS NEEDS—

INTEGRATE AUTONOMIC WITH VOLUNTARY MOTOR BEHAVIORS—

MEDIATES BALANCE OF SYMPATHETIC AND PARASYMPATHETIC ACTIVITY IN RESPONSE TO SYSTEMIC AND PSYCHOGENIC STRESS

CAUSE INVOLUNTARY PHYSIOLOGICAL CHANGES ASSOCIATED WITH CONSCIOUS EMOTIONAL OR PSYCHOGENIC STRESSORS

Front 157

What is the ANS's function in homeostasis?

Back 157

HOMEOSTASIS—Regulation of vital functions for survival and maintenance of life functions: metabolism, circulation, respiration, thermoregulation, fluid/electrolyte balance, digestion, excretion, and reproduction.

Front 158

What is the ANS role in motivating voluntary and involuntary behaviors?

Back 158

MOTIVATE BEHAVIORS/ACTIONS TO MEET SYSTEMIC HOMEOSTASIS NEEDS—Controls involuntary responses and also initiates/motivates voluntary behavior to meet internal/systemic status needs. Example: sweat when hot (involuntary), strip off layers to cool down (voluntary).

Front 159

Describe how the ANS INTEGRATEs AUTONOMIC WITH VOLUNTARY MOTOR BEHAVIORS

Back 159

INTEGRATE AUTONOMIC WITH VOLUNTARY MOTOR BEHAVIORS—running, climbing, position changes are voluntary actions with metabolic, thermoregulatory, and circulatory requirements automatically met by the actions of the ANS through changes in cardiac output, ventilation, and regional blood flow.

Front 160

ANS role in balancing SNS and PsNS

Back 160

MEDIATES BALANCE OF SYMPATHETIC AND PARASYMPATHETIC ACTIVITY IN RESPONSE TO SYSTEMIC AND PSYCHOGENIC STRESS—modulate responses by shifting the balance between Sympathetic and Parasympathetic outputs to meet demands. Both systems are on at the same time, all the time. Example: At rest, PNS stimulation of the heart is > than SNS stimulation of the heart.

Front 161

ANS - CAUSE INVOLUNTARY PHYSIOLOGICAL CHANGES ASSOCIATED WITH CONSCIOUS EMOTIONAL OR PSYCHOGENIC STRESSORS

Back 161

CAUSE INVOLUNTARY PHYSIOLOGICAL CHANGES ASSOCIATED WITH CONSCIOUS EMOTIONAL OR PSYCHOGENIC STRESSORS—Feeling of fear, anger, sadness, anxiety, happiness have characteristic autonomic manifestations. Example: flush when feeling embarrassed, cold sweat and pounding heart when afraid or anxious, tears when sad. Note: these involuntary responses are NOT the same as facial expressions and non-verbal behaviors caused by the basal ganglia.

Front 162

What is the Organization of ANS structures?

Back 162

THE ANS IS BOTH A HIERARCHICAL SERIAL PROCESSING AND A PARALLEL DISTRIBUTED PROCESSING SYSTEM:

Front 163

How is THE ANS A HIERARCHICAL SERIAL PROCESSING SYSTEM:

Back 163

Hierarchy—serial/sequential processing of ANS afference with efferent responses in every region of the nervous system including out in the periphery at the local tissue/organ, the spinal cord, brainstem, subcortical/diencephalon (hypothalamus), and cortical levels.

Example: central coordination of systemic vascular responses (skin, muscle, visceral) to exercise to meet metabolic and thermoregulatory needs can be modified at the local tissue muscle bed based on local status demands for blood flow.

Front 164

How is the ANS A PARALLEL DISTRIBUTED PROCESSING system?

Back 164

Parallel distributed processing—simultaneous action of information, divergence. layers of processing at the tissue bed, spinal cord, brainstem, subcortical and cortical levels occur simultaneously.

Example: Thermoregulation: local tissue bed reactions such as a skin response to temperature change that can be independent of a centralized thermoregulatory response coordinated by the hypothalamus to meet local needs without compromising central goals. Outdoors running in cold weather the exposed skin will have its own tissue level vasoconstriction response; however, the rest of the body will manage heat release built up with exercise with sweating and skin vasodilation in the areas protected by clothing.

Front 165

Each level of the hierarchy receives direct sensory afference from autonomic receptors in the body “bottom-up”
AND

Back 165

Each level of the hierarchy receives direct sensory afference from autonomic receptors in the body “bottom-up”
AND
“top-down” afference that has been processed by other levels or structures in the CNS. This processed afference puts the incoming afference “in context” with the overall body status.

AND

Each level can send descending control directly to the SNS and PNS pre-ganglionics to influence ANS outputs
AND

each level is reciprocally connected to the others and can influence the activity in another level to achieve the overall homeostatic goal.

Front 166

ANS
Systemic stimuli—”bottom-up”

Psychological/emotion stimuli—”top-down”

Back 166

Systemic stimuli—”bottom-up” physical inputs about the body’s homeostatic environment giving immediate info about systemic status. Physical stressors such as blood loss, infection and pain

Psychological/emotion stimuli—”top-down” inputs. Responds to non-physical or “psychogenic” stressors based on prior experience or innate programs and can occur in anticipation of or in reaction to stressful events.

Front 167

THE ANS IS BOTH A FEEDBACK/REACTION SYSTEM AND A FEEDFORWARD/ANTICIPATORY SYSTEM—

FEEDBACK--REFLEXES:

Back 167

FEEDBACK--REFLEXES: Autonomic reflex responses can be elicited at the tissue bed, spinal cord and brainstem levels by incoming sensory input that trigger a response:
Tissue Bed: Local skin response to temperature change—if heat the skin in one spot, sweat without the whole body sweating. If the exposed skin is cooled (wind/snow on your face) the blood vessels will vasoconstrict in that area to protect the skin, but not covered skin areas
Spinal Cord Reflex: Micturition/bladder reflex—when the bladder fills with urine, the bladder walls stretches. This stimulus is conveyed to the spinal cord where it synapses on a PNS efferent to the bladder wall/destrusor muscle to make it contract to expel urine.

Brainstem Reflex: Baroreflex—pressure stimulation in aorta & carotid arteries is transmitted via CN IX & X to nucleus of solitary tract (NST) which integrates the inputs, gives info to medullary cardiovascular center which will stimulate preganglionics of SNS in the SC and vagus nerve

Front 168

THE ANS IS BOTH A FEEDBACK/REACTION SYSTEM AND A FEEDFORWARD/ANTICIPATORY SYSTEM—
FEEDFORWARD ANTICIPATORY

Back 168

FEEDFORWARD ANTICIPATORY Autonomic responses can be initiated by “central command” from the cingulate cortex and by emotional stimuli from the amygdala and the insula to the hypothalamus. Example: anticipatory changes in heart rate, blood pressure, and sweating prior to onset of exercise or with anticipation of an upcoming speech to give providing an emotional/mental stressor.

Front 169

2. SNS vs. PSNS: peripheral targets/effects, peripheral efferent pathways, and neurotransmitters

Co-regulation for visceral function for homeostasis in everyday life:

Back 169

The SNS and PSNS play complementary and antagonistic roles to each other.

Co-regulation for visceral function for homeostasis in everyday life: the activity of the SNS and PSNS are tightly integrated, active together at all times, for example they work together to mediate bowel/bladder and reproduction functions.

Front 170

2. SNS vs. PSNS: peripheral targets/effects, peripheral efferent pathways, and neurotransmitters

Back 170

SNS: Promotes arousal, defense, and escape via the “Stress” responses—mobilizes and mediates the processes that use body resources to respond to a challenge and that allow the body to either “Fight, flight, or freeze” Increases energy expenditure.

Stressors/challenges:
Systemic—Exercise, Pain, Position change, Temperature change, fluid/electrolyte imbalance
Psychogenic/Emotion—fear, danger, anxiety, sadness

PNS: Promotes eating and reproduction. Rest/Digest—mediates processes that restore expended resources to replenish the body

The SNS and PSNS play complementary and antagonistic roles to each other.

Front 171

Sympathetic Target Tissues

Back 171

Organs of head, neck, thoracic, abdominal, and pelvic regions.
(also PSNS)

Adrenal medulla—releases nor-epinephrine and epinephrine
Sweat glands in skin
Piloerector muscles of hair

ALL vascular smooth muscle—skin, muscle, organs
SNS is distributed to essentially all tissues (because of vascular smooth muscle).

When active, the SNS has a coordinated effect on multiple effectors throughout the body. This is augmented by SNS activation of the adrenal medulla.

Front 172

Parasympathetic Target Tissues

Back 172

Parasympathetic Target Tissues
Organs of head, neck, thoracic, abdominal, and pelvic regions.
(also SNS)
Parasympathetic system DOES NOT innervate skeletal or skin blood vessels or skin sweat glands/piloerector muscles for goose bumps.

When active, the PNS has a focal effect on an individual effector

Front 173

how does SNS innervation get to the body wall?

Back 173

Sympathetic innervation of the body wall “hitches a ride” with the spinal nerves.
Every spinal nerve has a gray ramus that carries SNS postganglionic fibers. Preganglionics PARAVERTEBRAL GANGLIA C1-S5 Spinal Nerves Targets

Skin—blood vessels vasodilate, vasoconstrict, sweat glands, & piloerector muscles

Skeletal Muscle—blood vessels vasoconstrict/vasodilate

Front 174

What spinal nerves are supplied by SNS cells from which levels? (you know what I mean...)

Back 174

T1-T4 preganglionics->
Superior Cervical paravertebral Ganglia->
head/neck C2-C4 spinal nerves

T3-T6 pre->
Cervical & upper thoracic ganglia ->UE C5-T1 spinal nerves

T1-T12 pre->Thoracic ganglia->trunk

T11-L2 pre-> lumbosacral ganglia->lower extremities

Front 175

Sympathetic innervation of the eye, salivary glands, and sweat gland/blood vessels in the face.

Back 175

Sympathetic innervation of the eye, salivary glands, and sweat gland/blood vessels in the face.
T1-T4 preganglionics  Cervical PARAVERTEBRAL GANGLIA follow the arteries into the skull to innervate their targets
Dilate pupil/raise eyelid
Inhibit Lacrimal/nasal glands
Inhibit Salivary glands or produce viscous secretions

Sweat glands/blood vessels/pilo-erector in face

Front 176

Sympathetic innervation of Thoracic cavity: Heart & Lungs.

Back 176

Sympathetic innervation of Thoracic cavity: Heart & Lungs.

T1-T5 preganglionicsCervical & upper thoracic PARAVERTEBRAL GANGLIAfollow arteries to innervateTargets

Bronchi: bronchodilation
Heart: chronotropic & ionotropic effects

Front 177

Sympathetic innervation of Abdominal and Pelvic organs.

Back 177

Sympathetic innervation of Abdominal and Pelvic organs.

T6-L2 preganglionics become the Splanchnic outflow and then synapse on the PREVERTEBRAL GANGLIA postganglionic fibers follow the arteries to innervate targets

Controls blood flow to organs.

T6-T12
Liver, pancreas: mobilize energy supplies, release stores
Stomach, Large, small intestine: inhibit digestion
T12-L2
Reproduction: stimulate ejaculation, orgasm
Rectum, bladder: relax walls to permit storage, contract sphincters to hold.

Front 178

During high levels of SNS activity “stress” response to physical or psychogenic/emotional challenge:

Back 178

The pupils dilate & eyelids retract enhance opportunity to see danger

Bronchi dilate maximize oxygenation.

Heart rate and contractility increase, peripheral blood vessel constriction increases to increase blood pressure  maximize perfusion to the brain and working muscles.

Blood flow to the gut is constricted while blood flow to working muscles is increased optimize blood flow to working muscles to meet demands for oxygen and fuel.

Epinephrine and norepinephrine are released from adrenal gland stimulating catabolic processesbreak down stored energy and mobilize into the blood stream for fuel.

Digestion, reproduction, and other anabolic growth functions are inhibited divert all energy to respond to the challenge. Salivation is inhibited, mouth dries.

Rectum and bladder are relaxed and internal sphinters activated permits more storage so no need to stop to go—or may cause quick release to lessen weight to carry.

Front 179

Parasympathetic innervation of the eye, salivary glands, thoracic and abdominal organs.

Back 179

Parasympathetic innervation of the eye, salivary glands, thoracic and abdominal organs.

CN III Oculomotor nerve: from midbrain Edinger-Westphal nucleus
constrict pupil
lens convexity for accomodation
 
CN VII facial/CNIX glossopharyngeal nerves: from pons Superior/inferior salivatory nucleus
stimulate tears and watery saliva (drooling)
 
CN X Vagus Nerve: from medulla Dorsal Motor Vagal Nucleus & Nucleus Ambiguus

Heart- slows heart rate
Lungs- slow breathing rate, bronchoconstriction and increase brochial secretions
Liver & Pancreas- increase storage of energy
Stomach, small intestine, proximal large intestine- stimulate secretions and digestion/motility

Front 180

Parasympathetic innervation of the pelvic organs.

Back 180

Parasympathetic innervation of the pelvic organs.

S2-S4 pelvic nerve
Rectum- contract wall & relax internal sphincter to empty rectum
Bladder- contract wall and relax internal sphincter to empty bladder
Reproduction/Genitals- promote reproduction, arousal response (erection and engorgement/lubrication)

Front 181

PSNS activation causes:

Back 181

PSNS activation causes:

The pupils to constrict.

The convexity of the lens to focus on close objects.

Bronchi will constrict. Secretions released.

Heart rate slows and contractility is reduced.

Digestion, reproduction, and other anabolic growth functions are stimulated so that all energy stores can be replenished. Salivation is stimulated.

Rectum and bladder are contracted to permit evacuation of stored urine and feces-now that the stress is gone it is time to go!

Front 182

All ANS pre-ganglionic neurons release ____ onto a _____ receptor.

Back 182

All pre-ganglionic neurons release Acetylcholine onto a cholinergic nicotonic (ionotropic) receptor.

Front 183

One pre-ganglionic SNS will project to _______
neurons -
PSNS preganglionic effects are targeted to a specific _____

Back 183

One pre-ganglionic SNS will project to multiple SNS post-ganglionics
neuronsDivergence in information assists with broad coordinated response across multiple effector organs.

PSNS preganglionic effects are targeted to a specific post-ganglionic group near the actual effector.

Front 184

SNS post-ganglionics release _____ onto adrenergic receptors—there are ___ classes of adrenergics with different effects

Back 184

SNS post-ganglionics release Norepinephrine onto adrenergic receptors—there are 4 classes of adrenergics with different effects

Front 185

PSNS post-ganglionics release ____ on ____ receptors

Back 185

PSNS post-ganglionics release Acetylcholine on cholinergic muscarinic (metabtropic) receptors

Front 186

The alpha motor neuron also uses what neurotransmitter onto what receptors?

Back 186

The alpha motor neuron also uses Acetylcholine onto nicotinic receptors

Front 187

Distribution of NE adrenergic receptor subtypes in SNS:

Back 187

Distribution of NE adrenergic receptor subtypes in SNS:

α1: vasoconstrict skin blood vessels, contract sphincter, dilate pupil
α2: vasoconstrict blood vessels in muscle, organs
β1: increase heart rate, contractility
β2: dilate bronchi, relax bladder wall, dilate muscle blood vessels

Front 188

Distribution of Ach cholinergic receptor subtypes:

Back 188

Distribution of Ach cholinergic receptor subtypes:

Nicotinic receptors: found on all post-ganglionic cell bodies and at NMJ
Muscarinic: all PSNS postganglionics, sweat glands of skin (by SNS)

Front 189

SNS vs. PSNS: neurotransmitters and receptors revisited—summary

Back 189

SNS vs. PSNS: neurotransmitters and receptors

PSNS and SNS preganglionics are cholinergic because use Acetylcholine on ionotropic (nicotonic) receptors (just like at the neuromuscular junction)

SNS postganglionic are adrenergic because use norepinephrine (NE) for all postganglionic outputs except the sweat glands (uses Acetylcholine). Effects differ per receptor subtype in the SNS (key concept for pharmacology).

PSNS postganglionics are cholinergic use Acetylcholine (Ach) on metabotropic (muscarinic) receptors

Front 190

Peripheral ANS Receptors and Pathways:

Back 190

Peripheral somatosensory info for the ANS is gathered by receptors in the viscera, skin, and muscle by:
Spinal nerves in C2-S5 carry ANS afference from the periphery. Synapse on 2o neurons in the spinal cord to ascend in the the “spino-other” ascending pathways to the brainstem and to the VPM of the thalamus to relay to the limbic cortex. Also synapses on neurons that will ascend in the dorsal columns systems to assist with localization. Both contribute to referred pain (see next slide).
Cranial nerves: Vagus nerve (CN X), Glossopharyngeal (CN IX). Carry general visceral sensory inputs from thoracic and upper abdominal organs, as well as from baroreceptors and chemoreecptors in the aorta/carotic arteries. Project directly to the brainstem Nucleus of the Solitary Tract. (Also includes CNVII/IX for taste).

Front 191

What peripheral receptors do the different ANS sensations use?

Back 191

Pain/Noxious stim such as ischemia or mechanical compression or burn/cold. Nocieptors—all viscera, blood vessels, skin, muscle
Thermal—skin and internal temperature. Thermosensation not only affects our comfort, but is also essential for survival. Thermoreceptors—skin afferents C and Aδ
Chemical—blood concentration of O2, CO2, H+, electrolytes, metabolites, glucose. Chemoreceptors—muscle afferents III, IV fibers: in GI tract to stimulate digestion Carotid bodies CN IX Taste receptors CNVII, IX
Mechanical—pressure, stretch/distention Mechanoreceptors—muscle afferents III, IV fibers; stretch of bladder/rectum, Distention of GI tract

Front 192

Central ANS receptors:

Back 192

Central ANS receptors: The hypothalamus itself has receptors that detect information directly about internal status from blood flow and CSF.
Thermo-receptors for core-temperature: contains warm-sensitive & cold-sensitive neurons that fire when blood core temp is above or below set temp.
Chemo-receptors: for electrolyte, glucose, fluid balance

Front 193

Something new for the dorsal columns system.
“In the last decade, it has become clear that _____ sensory information, especially that related to _____ visceral sensations, also ascends the central nervous system by another spinal pathway.

Back 193

“In the last decade, it has become clear that visceral sensory information, especially that related to painful visceral sensations, also ascends the central nervous system by another spinal pathway.

Second- order neurons whose cell bodies are located near the central canal of the spinal cord send their axons through the dorsal columns to terminate in the dorsal column nuclei, where third- order neurons relay visceral nociceptive signals to the ventral posterior thalamus and the insula.

Although the existence of this visceral pain pathway in the dorsal columns complicates the simplistic view of the dorsal column– medial lemniscal pathway as a discriminative mechanosensory projection and the anterolateral system as a pain pathway, mounting empirical and clinical evidence highlights the importance of this newly discovered dorsal column pain pathway in the central transmission of visceral nociception.”
From sinaeur 5th edition.

Front 194

Referred pain from abdominal organs: mechanisms for sensory perception.
Pain from visceral organs is perceived by the brain as coming from the body wall due to the

Back 194

Pain from visceral organs is perceived by the brain as coming from the body wall due to the convergence of visceral and somatosensory pain info onto a common 2o neuron in the spinal cord dorsal horn—both ALS and Dorsal columns systems (see previous slide).
Unlike somatic pain which is sharp and well-localized, visceral pain is usually perceived as a poorly localized ache.

Front 195

4. Central Autonomic Network: cortical, subcortical, and brainstem structures and distributed processing loops

Insula, Anterior Cingulate, Amygdala:
Hypothalamus is
Dorsal nucleus of vagus, Nucleus Ambiguus, Intermediolateral cell column and sacral nuclei:
PAG, PBN, NST and Reticular Formation regions:

Back 195

several hierarchical loops between these reciprocally connected structures with more complexity of ANS function forming layers of distributed parallel processing
Insula, Anterior Cingulate, Amygdala: Cortical and subcortical structures consciously perceive internal status/systemic inputs as well as emotional/psychogenic status and integrate them to motivate autonomic and voluntary behavior.

Hypothalamus is the “effector control hub” of homeostasis.
Dorsal nucleus of vagus, Nucleus Ambiguus, Intermediolateral cell column and sacral nuclei: Preganglionic cell boides for effectors of SNS and PSNS.
PAG, PBN, NST and Reticular Formation regions: Brainstem structures receive direct sensory afference for reflex control of cardiovascular, respiratory, thermoregulation, bowel/bladder control, and pain modulation. Recruited by the hypothalamus for coordinated response to systemic and psychogenic stressors.

Afferent input: to SC & BS for processing and reflex responses.

Front 196

4. Central autonomic network loops part 1: subcortical and cortical integration for “top-down” regulation
region: Limbic

Back 196

ANS Output:
Cortical Region: Limbic
Anterior Cingulate gyrus: initiates/motivates voluntary motor and autonomic responses to meet internal needs both systemic & psychogenic. Top down inputs to hypothalamus.

Subcortical:
Amygdala: provides emotional significance to sensory stimuli and initiates coordinated ANS, endocrine, and motor behavior responses to emotional stimuli especially fear. Top down inputs to hypothalamus.

Hypothalamus—see next slide

ANS Input:
Insula: 1o visceral sensory cortex. Conscious perception of all visceral sensation and taste. Top down inputs to hypothalamus.

Front 197

4. Central Autonomic Network

The hypothalamus is the “effector control hub” of homeostasis.
The hypothalamus receives the ___ and ___ inputs and integrates them in order to control and to recruit the optimal:

Back 197

The hypothalamus receives the bottom-up and top-down inputs and integrates them in order to control and to recruit the optimal:

1. Autonomic physiological responses through descending outputs to the SNS and PSNS preganglionics.

2. Voluntary behavioral responses via ascending inputs to the cortex

3. Neuroendocrine outputs via connections to the posterior pituitary gland (i.e., HPA axis)

Front 198

4. Central autonomic network loops part 2: hypothalamic, brainstem and spinal reflex loops of parallel distributed processing and immediate response to bottom up info.

Back 198

ANS Output:
Brainstem centers: Parts of the reticular formation & NST can implement brainstem level reflex responses to systemic inputs that are regulated by descending info from hypothalamus.

Spinal Cord—local reflex loops
Collaterals synapse on preganglionic neurons in the intermediolateral cell column for SNS T1-L2 or S2-S4 for a spinal cord reflex loop with SNS or PNS preganglionics. Note this information can be widely distributed across the sympathetic chain.

Collateral synapse on somatic efferents—to skeletal muscle. Example: muscle guarding with pain, inhibit external bladder sphincter

ANS Input
Brainstem centers:
PBN (Parabrachial nucleus) and Parts of the reticular formation receive bottom up directly and processed from NST, project to subcortical and cortical centers.

Nucleus of the solitary tract—see next slide NST

Front 199

The nucleus of the solitary tract in the ___ is the central structure in the brain that receives ____ from the ____ (ascending ____ tracts & ____ nerves) and distributes it to:

1.

2.

Back 199

The nucleus of the solitary tract in the medulla is the central structure in the brain that receives visceral sensory information from the body (ascending spino-other tracts & cranial nerves) and distributes it to:

1. Provide feedback to local reflexes that modulate moment- to- moment visceral motor activity within individual organs. (see previous slide)

2. Inform higher integrative centers of more complex patterns of stimulation that may signal potentially threatening conditions and/ or require the coordination of more widespread visceral motor, somatic motor, neuroendocrine, and behavioral activities.

Front 200

5. Specific functions and examples of dysfunctions of the ANS: cardiovascular regulation
1. Resting vitals signs:

Back 200

1. Resting vitals signs:
Vagal tone-> HR
Sympathetic tone -> peripheral resistance

Front 201

5. Specific functions and examples of dysfunctions of the ANS: cardiovascular regulation
2. Baroreflex

Back 201

2. Baroreflex
Pressor- increase BP/HR
Depressor -decrease BP/HR to maintain BP at set point.

CNIX, CNX afference- NTS - medulla RF- PSNS, SNS activation

Front 202

5. Specific functions and examples of dysfunctions of the ANS: cardiovascular regulation


3. Respiratory sinus arrhythmia:

Back 202

3. Respiratory sinus arrhythmia: assesses presence of vagal tone on heart
Inhale - increase HR
Exhale- decrease HR

Front 203

5. Specific functions and examples of dysfunctions of the ANS: cardiovascular regulation
4. Problematic responses to stress:

Back 203

4. Problematic responses to stress:
Position change vs. gravity—orthostatic hypotension:
-> BP drops, HR rises

Vasovagal response
-> BP drops, HR drops

Autonomic dysreflexia after SCI (see next slide)
-> BP increases, HR drops

Front 204

Autonomic Dysreflexia: Occurs in

Back 204

Autonomic Dysreflexia: Occurs in individuals with SCI T6 and above.

Triggered by a noxious stimulus below the level of the lesion, which then activates unopposed sympathetic activity. The noxious stimulus is carried by intact sensory nerves below the level of the lesion to the spinal cord and activates sympathetic nerves, causing massive vasoconstriction and increased BP. The increased BP is sensed by baroreceptors in the carotid and aortic arch and activates parasympathetic nerves above the lesion to counter the sympathetic response.
Sit the patient upright and lower the legs to reduce BP.

Find source of noxious stimuli.

Front 205

5. Exercise Response: SNS and PSNS activation to

Back 205

5. Exercise Response: SNS and PSNS activation to
Increase HR
Increase BP
Maintain perfusion to brain, exercising muscles, heart muscle

Front 206

5. Specific functions and examples of dysfunctions of the ANS: bowel/bladder function

Back 206

Bladder & Bowel control: parallel and hierarchical complementary activation of SNS & PSNS

Structures:
Smooth muscle: Skeletal muscle:
Detrusor muscle/bladder wall -External sphinct
Internal sphincter

Efferent Innervation:
PNS S2-S4 pelvic nerve -> contract detrusor muscle, relax internal sphincter—Urinate
SNS T11-L2 hypogastric nerve -> relax detrusor muscle, contract internal sphincter—Hold it
Somatic S2-S4 pudendal nerve -> contract external sphincter (tonically active)—Hold it

Front 207

To Urinate: STRETCH SIGNAL
3 levels

Back 207

To Urinate: STRETCH SIGNAL
Level 1
Spinal cord: Sacral reflex arc
Stretch signal stimulates PSNS and inhibits somatic.

Level 2

Brainstem Micturition Center: coordinates PSNS, SNS and somatic efferent output
Stretch signal to brainstem -descending info inhibits SNS, inhibits somatic and stimulates PSNS
Level 3

Cortex: voluntary initiation of urination. Stretch signal -to cortex - descending info collateral to brainstem micturition center

Front 208

To hold it: (prevent urination)

Back 208

To hold it:
Brainstem descending info: Inhibit PNS and Stimulate SNSnet effect is to relax the bladder wall and contract the internal sphincter.

Cortex: descending info: stimulate somatic and inhibit sacral reflex arc

Front 209

5. Specific functions and examples of dysfunctions of the ANS: Horner’s syndrome
Presentation:
Can occur from:

Back 209

5. Specific functions and examples of dysfunctions of the ANS: Horner’s syndrome
Horner’s Syndrome: Ipsilateral loss of sympathetic tone to the head/neck.

Presentation: Pupil constriction, mild ptosis, and loss of sweat & vasoconstriction on half of the face (or body).
Diagram of the sympathetic pathways to the head/neck.

Horner’s syndrome can occur from
Damage to descending ANS pathways from the hypothalamus and reticular formation—loss of sweat, vascular control on half of the body & head/neck.
Damage to the preganglionic neurons in the upper thoracic cord -head and neck only
Damage to the superior cervical ganglion, or to the cervical sympathetic trunk -head and neck only

Front 210

All sensory systems have a specific type of stimulus that they transduce with a population of different receptors. The receptors are connected to afferent fibers that make synaptic connections on other neurons in different locations—multiple parallel pathways.

The parallel pathways project

Back 210

All sensory systems have a specific type of stimulus that they transduce with a population of different receptors. The receptors are connected to afferent fibers that make synaptic connections on other neurons in different locations—multiple parallel pathways.

The parallel pathways project the sensory information to the sensory cortex for conscious perception, to the brainstem to different nuclei that will mediate reflexive and automatic responses, and from the brainstem to the cerebellum. In the case of somatosensation, the inputs can also stay in the spinal cord to mediate reflexes as well as adjust the outputs of central pattern generators and synergies. There are also direct somatosensory pathways that project to the spinocerebellum.

Front 211

Modality:
Transduce:
Encode:

Back 211

Modality: a particular sensation that is perceived
Transduce: transform an external stimulus into an electrical signal
Encode: decomposition of a sensory stimulus by a population of receptors into action potential messages within the different afferent fibers

Front 212

Which sensory systems use mechanoreceptors?

Back 212

Hearing - hair cells
Vestibular - hair cells
Somatosencory: touch, Proprioception, and pain

Front 213

Which sensory systems use chemoreceptors?

Back 213

Gustatory - Taste
Olfactory - Smell
Somatosensory: pain and itch

Front 214

Which sensory systems use thermoreceptors?

Back 214

Somatosensory: Temperature and pain

Front 215

SENSORY PROCESSING—
PRIMARY & SECONDARY CORTICAL AREAS

Back 215

SENSORY PROCESSING—somatosensation, vision, auditory, and vestibular
PRIMARY & SECONDARY CORTICAL AREAS
Primary—discriminate individual sensory components and localize
Secondary—integrate combination of sensory components from one system(unimodal) or from two systems (bimodal)

Front 216

Function of primary somatosensory area

Back 216

Discriminate temp, sharp pain, dull, light touch, 2 pts and localize in/on body
Area 3,2,1

Front 217

Function of primary visual area

Back 217

distinguishes intensity of light, shape, size, and location of objects
Area 17

Front 218

Function of primary auditory area

Back 218

Conscious discrimination of loudness and pitch of sounds
Area 41

Front 219

Function of primary vestibular area

Back 219

Discriminates among head positions and head movements
Anterior area 40

Front 220

Function of secondary somatosensory area area

Back 220

Somatosensory Association area
Integrate somatosenssory inputs to form object properties, direction/velocity of motion(40), integrate with vision for goal coordinates (5.7).
Area 5,7

Front 221

Function of secondary visual area

Back 221

Visual association area
Analysis of motion, color; control of visual fixation
Area 18-21

Front 222

Function of secondary auditory area

Back 222

Auditory association area
Classification of sounds
Area 22, 42

Front 223

ASSOCIATION CORTICES—

Back 223

ASSOCIATION CORTICES—integration of multiple sensations for perception and for motor planning decision—
Provides Movement Intention/Purpose: why you will move, what is the goal to achieve with the movement?

Logic/cognition
Spatial/experience
Emotion

Dorsolateral prefrontal association: goal-oriented behavior, self awareness (light blue areas - lateral 8&9, 46)
Parietotemoral association: sensory integration, problem solving, understanding language and spatial relationships (green areas - 39,40, parts of 7, 19, 21, 22, 37)
Ventral and medial dorsal prefrontal association: emotion, motivation, personality (yellow/green ventral areas - 11, 44, 45, 47. Medial dorsal - medial 8 & 9, 10)

Front 224

MUSCLE AFFERENT nerves:

Back 224

MUSCLE AFFERENTS:
Ia—muscle spindle primary =Aα
II—secondary
Ib—GTO
II—Joint capsule
III—stretch sensitive excess
IV—chemo sensitive excess

Front 225

Modalities for myelinated sensory afferent nerves
A alpha
A Beta
A Delta

Back 225

Modalities for myelinated sensory afferent nerves
A alpha - proprioceptors from muscles and tendons
A Beta - low threshold mechanoreceptors
A Delta - cold, noxious, thermal

Front 226

Modalities for unmyelinated sensory afferent nerves
C- pain
C - tactile
C - autonomic

Back 226

Modalities for unmyelinated sensory afferent nerves
C- pain: noxious, heat, thermal
C - tactile: light stroking, gentle touch
C - autonomic: autonomic, sweat glands, vasculature

Front 227

Which sensory receptors rapidly adapt? phasic

Back 227

Hair follicles - light brush
Meissner Corpuscles - dynamic deformation
Pacinian Corpuscles - vibration

Front 228

Which sensory receptors slowly adapt? keep responding to stimulus, tonic

Back 228

Merkel cell-neurite complex: indentation depth (fine tactile discrimination; form and texture perception)
Ruffini Corpuscle: stretch (direction of object motion, hand shape and finger position)
C-fiber LTM: touch (pleasant contact)
Mechano-nociceptor and polymodal nociceptor: injurious forces (skin injury, pain)

Front 229

1st pain vs 2nd pain

Back 229

1st pain - discriminative, fast Adelta fibers
2nd pain - affective, C fibers

Also 1st touch (fast Abeta identification) and 2nd touch (slow c-fiber, positive emotional attributes)

Front 230

What types of fibers are involved in muscle spindles?
golgi tendon organs?

Back 230

1a afferents
group II afferents - secondary at ends
Gamma (γ) motorneuronensure senstivity of muscle spindle when muscle length changes.

Golgi:
1b afferent

Front 231

TWO CONSCIOUS ASCENDING SYSTEMS for sensory discrimination & localization:

TWO NON-CONSCIOUS AND LIMBIC/EMOTIONAL ASCENDING SYSTEMS

Back 231

TWO CONSCIOUS ASCENDING SYSTEMS for sensory discrimination & localization:
“Fast” with relay in the thalamus
VPL for body
VPM for face

DORSAL COLUMNS: Discriminative touch, Position

ANTERO-LATERAL SYSTEM: Pain, Temperature, Crude Touch, Itch

TWO NON-CONSCIOUS AND LIMBIC/EMOTIONAL ASCENDING SYSTEMS

SPINOCEREBELLAR TRACTS: mechanoreceptor information to cerebellum

SPINO-OTHER TRACTS: SLOW fiber information to brainstem and limbic cortex

Front 232

CORTICAL SOMATOSENSORY PROCESSING
PRIMARY & SECONDARY

Back 232

CORTICAL SOMATOSENSORY PROCESSING
PRIMARY & SECONDARY

Primary—discriminate individual sensory components and localize i.e. “sharp on tip of index finger” AREA 3, 1, 2
Discriminate temp, sharp pain, dull, light touch, 2 pts and localize in/on body

Secondary—AREA 5, 7 dorsal stream for movement
Integrate somatosenssory inputs to form object properties, direction/velocity of motion(40), integrate with vision for goal coordinates (5.7).

SII area just posterior to AREA 2 integrate combination of sensory components into object properties“soft” “round” ventral stream

Front 233

Functions of areas 3,1,2

Back 233

3b and 1—respond to cutaneous inputs—discriminate, identify, localize sharp/dull, light touch, 2 point discrimination
3a responds to muscle inputs,
2 receives and integrates both skin and muscle inputs for conscious proprioception

Front 234

6 OBJECT PROPERTIES—cortical integration of somatosensory inputs
S1 -SII
Six "exploratory procedures"

Back 234

Six "exploratory procedures"
Lateral motion (texture)
Unsupported holding (weight)
Pressure (hardness)
Enclosure (global shape, volume)
Static contact (temperature)
Contour following (global and exact shape)

Front 235

UNCONSCIOUS PROPRIOCEPTION—Spinocerebellar tracts to the spinocerbellum

Back 235

Information that travels in the spinocerebellar tracts is not consciously perceived. Information in the spinocerebellar tracts is used for unconscious adjustments to movements and posture. Because the internal feedback tracts convey descending motor information to the cerebellum before the information reaches the motor neurons, and the high-fidelity pathways convey information from muscle spindles, tendon organs, and cutaneous mechanoreceptors, the cerebellum obtains information about movement commands and about the movements or postural adjustments that followed the commands. Thus the cerebellum can compare the intended motor output versus the actual movement output. (see next slide for more info on these 4 tracts)

Front 236

UNCONSCIOUS PROPRIOCEPTION—Relationship between incoming sensory afferents and the parallel pathway to the spinocerebellum. The primary afferent comes in from

Afferents from lower body:
Upper body:

Back 236

UNCONSCIOUS PROPRIOCEPTION—Relationship between incoming sensory afferents and the parallel pathway to the spinocerebellum. The primary afferent comes in from the body and can leave collaterals in the spinal cord.

Afferents from the lower body: The posterior (dorsal) spinocerebellar (pink) pathway transmits information from the legs and the lower half of the body. The proximal axon of the first-order neuron travels in the dorsal column to the thoracic or upper lumbar spinal cord, then synapses in the area of the dorsal gray matter called the nucleus dorsalis (Clarke's nucleus between T1-L2)

The cuneocerebellar pathway (purple) begins with primary afferents from the arm and upper half of the body—they will ascend to the brainstem and then project into the cerebellum.

Front 237

The anterior and rostrospinocerebellar tracts provide information to the cerebellum about the

Back 237

The anterior and rostrospinocerebellar tracts provide information to the cerebellum about the descending commands delivered to the neurons that control muscle activity via interneurons located between descending motor tracts and motor neurons that innervate muscles—they help to provide the efference copy. These internal feedback tracts also convey information about the activity of spinal reflex circuits so the cerebellum knows the spinal cord’s status.

The anterior spinocerebellar tract (on the previous slide) transmits information from the thoracolumbar spinal cord.

The rostrospinocerebellar tract (on the previous slide) transmits information from the cervical spinal cord.

Front 238

ANTERO-LATERAL SYSTEM—SLOW AFFERENT INFO:
Pathways for SLOW information:

Back 238

nociceptive, thermal, mechanical pleasurable touch and itch information.
Sites of synapse and termination for slowly conducted nociceptive information. Lateral and midsagittal views of the cerebrum, lateral and coronal views of the thalamus, and a horizontal view of the midbrain are illustrated. Stippled blue in the cerebral cortex and blue in the anterior cingulate cortex indicate the termination of the spinolimbic pathway. The blue areas in the midline and intralaminar nuclei of the thalamus indicate sites of synapse of the spinolimbic tract. Red indicates the termination of the spinomesencephalic tract in the superior colliculus and the periaqueductal gray. Green indicates the termination of the spinoreticular tract in the midbrain reticular formation.
Pain thalamic relays:
Localization of pain (where it hurts and what it feels like) goes to S1 via VPL/VPM
conscious affective component of pain uses dorsal intermediate nuclei and then goes to the cingulate area. (see next slide)

Front 239

Define inflammatory pain:
Peripheral Sensitization:
Central sensitization:

Back 239

pain hypersensitivity due to peripheral tissue inflammation involving the detection of active inflammation by nociceptors and a sensitization of the nociceptive system

Peripheral Sensitization: an increase in the sensitivity of the peripheral terminals of nociceptors due to a decrease in transduction threshold and an increase in membrane excitability

Central sensitization: an increase in synaptic strength in nociceptive circuits that results from synaptic facilitation or a reduction in inhibition

Front 240

Reticular nuclei, located in the brainstem, produce neurotransmitters that are slow acting or neuromodulating. The ascending fibers from reticular nuclei form the _______ system, which regulates activity in the cerebral cortex. Descending fibers adjust the ______ in the spinal cord.
A, The ventral tegmental area supplies ____ to the frontal cortex & limbic areas.
B, Pedunculopontine nucleus provides ___ to thalamus, frontal cerebral cortex, brainstem, & cerebellum, & facilitates reticulospinal tracts.
C, The raphe nuclei supply ____ to thalamus, midbrain tectum, striatum, amygdala, hippocampus, cerebellum, throughout the cerebral cortex, & to the spinal cord (raphespinal tract).
D, The locus ceruleus & medial reticular zone nuclei provide _______ in a wide distribution similar to the pattern of serotonin distribution. The tracts descending into the spinal cord are the medial reticulospinal and ceruleospinal tracts.

Back 240

Reticular nuclei, located in the brainstem, produce neurotransmitters that are slow acting or neuromodulating. The ascending fibers from reticular nuclei form the ascending reticular activating system, which regulates activity in the cerebral cortex. Descending fibers adjust the general level of activity in the spinal cord.
A, The ventral tegmental area supplies dopamine to the frontal cortex & limbic areas.
B, Pedunculopontine nucleus provides ACh to thalamus, frontal cerebral cortex, brainstem, & cerebellum, & facilitates reticulospinal tracts.
C, The raphe nuclei supply serotonin to thalamus, midbrain tectum, striatum, amygdala, hippocampus, cerebellum, throughout the cerebral cortex, & to the spinal cord (raphespinal tract).
D, The locus ceruleus & medial reticular zone nuclei provide norepinephrine in a wide distribution similar to the pattern of serotonin distribution. The tracts descending into the spinal cord are the m

Front 241

DESCENDING
Anti-nociceptive systems.
A, Tracts that convey ascending slow nociceptive information are shown on the left: the spinolimbic (blue), spinomesencephalic (red), and spinoreticular (green) tracts.

The five levels of the nervous system involved in pain inhibition are shown on the right. All tracts are bilateral. Signals in the spinoreticular tract facilitate the locus ceruleus neurons.

Back 241

DESCENDING
Anti-nociceptive systems.
A, Tracts that convey ascending slow nociceptive information are shown on the left: the spinolimbic (blue), spinomesencephalic (red), and spinoreticular (green) tracts.

The five levels of the nervous system involved in pain inhibition are shown on the right. All tracts are bilateral. Signals in the spinoreticular tract facilitate the locus ceruleus neurons.

I: peripheral
II: dorsal horn
III: fast-acting neuronal pathway from brainstem (PAG, locus ceruleus, raphe nuclei)
IV: hormonal (pituitary, b-endorphin, adrenals)
V: descending cortical inhibition

Front 242

Figure 07-11.   SPINAL CORD INPUTS FROM DESCENDING PAIN MODULATION SYSTEM

Back 242

Figure 07-11.   SPINAL CORD INPUTS FROM DESCENDING PAIN MODULATION SYSTEM

A segment of the spinal cord. The raphespinal tract synapses with an interneuron (black) that inhibits the transmission of nociceptive information in the dorsal horn of the spinal cord. The ceruleospinal tract directly inhibits the primary nociceptive afferent.

Front 243

Counterirritant mechanism—GATE THEORY

Back 243

Counterirritant mechanism—GATE THEORY
Circuits in the dorsal horn that may produce inhibition of nociceptive signals.

Collaterals of mechanoreceptive afferents stimulate interneurons that release enkephalins.

Enkephalin binding inhibits the transmission of nociceptive messages by primary afferents and interneurons in the nociceptive pathway.

The Gate Control Theory of Pain proposes that both large (A-fibers) and small (C-fibers) synpase onto cells in the substantia gelatinosa (SG) and the 1st central transmission (T) cells in Lamina 1 and 5. The inhibitory effect exerted by SG cells onto the primary afferent fiber terminals at the T cells is increased by activity in A-fibers and decreased by activity in C-fibers. The central control trigger is represented by a line running from the A-fiber systerm to the central control mechanisms; these mechanisms, in turn, project back to the Gate Control system. The T cells project to the entry cells of the action response systems, exci/inhibit

Front 244

The intraocular muscles—controlled by the ANS—will ____ the pupil and _____ the lens (____).

Back 244

The intraocular muscles—controlled by the ANS—will dilate/constrict the pupil and focus the lens (accomodation).

Front 245

There is a 3 neuron chain from where the light activates the photoreceptors and the axons for the optic nerve leaves the eye.

The PHOTORECEPTOR absorbs the photon of light, changing its membrane potential—leading to neurotransmitter release onto a ____ CELL—which then synapses on the ____ CELL.

It is the axons from the ____ cell that form the optic nerve.

Back 245

There is a 3 neuron chain from where the light activates the photoreceptors and the axons for the optic nerve leaves the eye.

The PHOTORECEPTOR absorbs the photon of light, changing its membrane potential—leading to neurotransmitter release onto a BIPOLAR CELL—which then synapses on the GANGLION CELL.

It is the axons from the ganglion cell that form the optic nerve.

Front 246

The rods and cones are specialized for different aspects of vision. They differ by

Back 246

The rods and cones are specialized for different aspects of vision. They differ by
the pattern of synaptic connections
what type of photons they transduce (see next slide)
their distribution across the retina (see 2 slides).

Several rods will converge their inputs onto a single ganglion cell. Thus one ganglion cell receives input from a large receptive field region of the eye. This make the rod system better at detecting low levels of light.

Individual cones synapse on individual ganglion cells. This provides high acuity of information as each receptor has a connection out of the eye.

Front 247

Types of photons transduced by rods vs cones

Back 247

The ROD SYSTEM has very low resolution for details, but they are very sensitive to the amount of light—rods can respond to a single photon of light.

They are responsible for vision in “the dark” but as light levels increase the rods stop responding.

They do not differentiate wavelengths of light


The CONE SYSTEM has very high spatial resolution providing high details, but they are insensitive to low levels of light—they make no contribution to night vision.
Instead they are responsible for vision in daylight and when the lights are on.

They also are sensitive to different wavelengths of light that convey color.

Front 248

The retina defines the limits of vision—the types of photoreceptors AND the density of those photo receptors determine the ability:

Back 248

The retina defines the limits of vision—the types of photoreceptors AND the density of those photo receptors determine the ability:

to resolve find details/acuity
to detect tiny movements
to detect subtle differences in color or contrasts of light.

For example:

Color blindness: Normally we have three different cones that detect short, medium and long wavelength light that becomes the rainbow of colors we can see (ROYgBIV). Without one of the cones, only two wavelengths of light can be seen.
Macular Degeneration: causes a progressive loss of central vision due to degeneration of the photoreceptors. Leads to blurred an eventually blind spots within the central visual field. There are no photoreceptors there to detect the light.

Front 249

Visual PATHWAY 1oafferent (red neuron) :

Ganglion cell in the Retina -> ...

Optic Tract Axons project to:

Back 249

PATHWAY 1oafferent (red neuron) :

Ganglion cell in the Retina -> optic NERVE -> optic CHIASM -> optic TRACT

Optic Tract Axons project to:
Superchiasmatic Nucleus of the hypothalamus
Pre-tectal region to the ANS nuclei
Superior colliculus
Lateral geniculate of the thalamus where it synapses on the 2o neuron. Those axons are thalamocortical projections that are named the optic radiation and are part of the internal capsule. They project to the visual cortex (a.k.a. “striate cortex”).

Front 250

Each eye receives information from both the right and left visual fields.

The nasal portion of the retina is aimed at the ______ visual fields (A and D in the figure on the left).

The temporal portion of the retina is aimed a the _______ (B and C in the figure).

Back 250

Each eye receives information from both the right and left visual fields.

The nasal portion of the retina is aimed at the peripheral visual fields (A and D in the figure on the left).

The temporal portion of the retina is aimed a the central visual field (B and C in the figure).

The optic nerve leaving each eye has axons from both visual the right and left visual fields. Axons from the nasal retina will cross in the optic chiasm—delivering peripheral vision. Therefore, the optic tract will have information from one visual field (either the left or the right). Therefore the right visual cortex will receive information from the left visual field.
Additionally the top portion of the visual field will be gathered by the inferior retina and the bottom of the visual field will be gathered by the superior retina. The fibers from the inferior retina will project in the lower part of the optic radiations.

Front 251

The retinogeniculostriate projection ( the primary visual pathway) is arranged topographically such that central visual structures contain an organized map of the contra-lateral visual field. Damage anywhere along the primary visual pathway, which includes the
optic nerve,
optic chiasm,
optic tract,
lateral geniculate nucleus,
optic radiation, and
striate cortex, results in a loss of vision confined to a predictable region of visual space.

Back 251

The retinogeniculostriate projection ( the primary visual pathway) is arranged topographically such that central visual structures contain an organized map of the contra-lateral visual field. Damage anywhere along the primary visual pathway, which includes the optic nerve, optic tract, lateral geniculate nucleus, optic radiation, and striate cortex, results in a loss of vision confined to a predictable region of visual space.
R optic nerve - Right visual field is gone (right peripheral and left central)
Optic Chiasm - L and R peripheral info (bitemporal hemianopsia)
Optic tract - right half of vision (info from L peripheral and R central) (left homonymous hemianopsia)
lateral geniculate nucleus,
optic radiation, (left superior quadrantonopsia - loss of vision from top left quadrant of both sides. Vision on lower right side?)
and
striate cortex (left homonymous hemianopsia with macular sparing - left sides of both eyes damaged but central area clear)

Front 252

Distinct populations of retinal ganglion cells send their axons to a number of central visual structures that serve different functions. The most important projections are to

Back 252

Distinct populations of retinal ganglion cells send their axons to a number of central visual structures that serve different functions. The most important projections are to the pretectum for mediating the pupillary light reflex; to the hypothalamus for the regulation of circadian rhythms; to the superior colliculus for the regulation of eye and head movements; and— most important of all— to the lateral geniculate nucleus for mediating vision and visual perception.

Front 253

Cortical pathways of visual perception after V1:

Back 253

Cortical pathways of visual perception after V1:
Vision for motion, location: Dorsal Stream (to posterior parietal cortex)
Vision for object identification: Ventral Stream (occipitotemporal region)

Front 254

Neural control systems for gaze stabilization

Back 254

Vestibulo-occular during rapid head movements - to keep gaze fixed on a target - reflex conjugate (eyes together) movement - command from vestibular nucclei

Optokinetic - to keep gaze fixed on an object during slow head movements - reflex conjugate - from visual cortex

Front 255

Neural control systems for direct gaze (Move eyes to optimize vision)

Back 255

smooth pursuit - maintain gaze on a moving target - voluntary conjugate - from visual cortex

saccadic - to rapidly move the eyes to a new target - voluntary conjugate - frontal eye fields

vergence - to align the eyes on a near target - voluntary disconjugate - visual cortex

Front 256

Vestibulo-ocular reflexes (VORs) stabilize visual images during head movements. This stabilizing prevents

Back 256

Vestibulo-ocular reflexes (VORs) stabilize visual images during head movements. This stabilizing prevents the visual world from appearing to bounce or jump around when the head moves, especially during walking. All VORs move the eyes in the direction opposite to the head movement to maintain stability of the visual field and visual fixation on objects.

Front 257

Normally, when the head turns to the right, signals from the right horizontal semicircular canal ____ and signals from the left horizontal semicircular canal ____. This information is relayed to the vestibular nuclei for coordination of visual stabilization. Information is sent from the vestibular nuclei to

If the intent is to look in the new direction when turning the head, rather than have the eyes fixate on the previous target,

Back 257

Normally, when the head turns to the right, signals from the right horizontal semicircular canal increase and signals from the left horizontal semicircular canal decrease. This information is relayed to the vestibular nuclei for coordination of visual stabilization. Information is sent from the vestibular nuclei to the nuclei of cranial nerves III and VI, activating the rectus muscles that move the eyes to the left and inhibiting the rectus muscles that move the eyes to the right. Similarly, vertical VORs can be elicited by flexion of the head and extension of the head.

If the intent is to look in the new direction when turning the head, rather than have the eyes fixate on the previous target, VOR suppression occurs. The flocculus of the cerebellum adjusts the gain of the VOR and can completely suppress the VOR when appropriate.

Front 258

Optokinetic means that

Back 258

Optokinetic means that the reflex is elicited by moving visual stimuli. It is a fast moving saccade designed to follow moving objects in the visual field. The optokinetic system allows the eyes to follow large objects in the visual field. Experimentally, the optokinetic system can be studied by having a person watch a cylinder covered with vertical stripes rotating slowly. A normal response is for the person's eyes to follow a single stripe to the edge of the visual field, and then a saccade moves the eyes to the next stripe.

Front 259

The frontal eye fields control _____ eye movements. Occipital and temporal regions provide information for _____ eye movements. The posterior parietal cortex provides ____ information for eye movements.
The areas colored blue provide information about...

Back 259

The frontal eye fields control voluntary eye movements. Occipital and temporal regions provide information for pursuit eye movements. The posterior parietal cortex provides spatial information for eye movements.
The areas colored blue provide information about the movement of visual objects, essential for optokinetic and smooth pursuit eye movements. The areas colored red are important for saccades.

Front 260

Lens of eye adjusts to focus light on the retina, pupil constricts, and pupils move medially when viewing an object at close range. During reading, the pupils are directed toward the _____ to allow the image to fall on corresponding areas of the retinas. This convergence is part of the accommodation reflex.
ACCOMODATION means that the lens ______ VERGENCE means that the eyes are ______. The efferent limb to move the pupils toward the midline is from the visual cortex to the frontal eye fields, then to the main oculomotor nucleus, then the oculomotor nerve, which controls contraction of the medial rectus muscles.

Back 260

Lens of eye adjusts to focus light on the retina, pupil constricts, and pupils move medially when viewing an object at close range. During reading, the pupils are directed toward the midline to allow the image to fall on corresponding areas of the retinas. This convergence is part of the accommodation reflex.
ACCOMODATION means that the lens will change shape to adjust the focal point on the retina. VERGENCE means that the eyes are directed medially due to cortical input. The efferent limb to move the pupils toward the midline is from the visual cortex to the frontal eye fields, then to the main oculomotor nucleus, then the oculomotor nerve, which controls contraction of the medial rectus muscles.

Front 261

GENERAL FUNCTIONS OF THE VESTIBULAR SYSTEM

Back 261

Sensory afference and perception about head movement, head position against gravity.

Gaze stabilization (see Vision slides)

Balance and Postural Control adjustments

Autonomic activation and arousal.

Front 262

GENERAL FUNCTIONS OF THE AUDITORY SYSTEM

Back 262

Sensory afference and perception of sound for language/communication as well as music and other non-verbal sounds.

Spatial orientation to sound for head/eye movement.

Increase autonomic activation and arousal.

Front 263

Stereocilia and Kinocilia: mechanical deflection opens/closes ion channels to create receptor potentials.

The auditory system transforms sound stimuli into

Back 263

Stereocilia and Kinocilia: mechanical deflection opens/closes ion channels to create receptor potentials.

The auditory system transforms sound stimuli into distinct patterns of neural activity. The frequency, amplitude, and phase of the original signal is transduced by the sensory hair cells and encoded by the electrical activity of the auditory nerve fibers. One product of this process of acoustical decomposition is the systematic representation of sound frequency along the length of the cochlea, referred to as tonotopy, which is an important organizational feature preserved throughout the central auditory pathways.

Front 264

The vestibular hair cells, like cochlear hair cells, transduce minute displacements into behaviorally relevant receptor potentials, provide the basis for vestibular function. The hair cell bundles in each vestibular organ have specific orientations. Thus, the organ as a whole is responsive to

Back 264

The vestibular hair cells, like cochlear hair cells, transduce minute displacements into behaviorally relevant receptor potentials, provide the basis for vestibular function. The hair cell bundles in each vestibular organ have specific orientations. Thus, the organ as a whole is responsive to displacements in all directions. In a given semicircular canal, the hair cells in the ampulla are all polarized in the same direction. In the utricle and saccule, a specialized area called the striola divides the hair cells into two populations having opposing directions. The directional polarization of the receptor surfaces is a principle of organization in the vestibular system,

Front 265

The three semicircular canals sense head rotations, arising either from

Back 265

The three semicircular canals sense head rotations, arising either from self- induced movements or from angular accelerations of the head imparted by external forces, such as a merry- go- round. Each of the three semicircular canals has at its base a bulbous expansion— the ampulla— that houses the sensory epithelium, or crista, that contains the hair cells.

Front 266

The two otolith organs— the utricle and the saccule— detect displacements such as

Back 266

The two otolith organs— the utricle and the saccule— detect displacements such as head tilts and linear accelerations of the head, such as translational movements forward/backward; up/down. Note that the saccular and utricular maculae on one side of the head are mirror images of those on the other side. Thus, a tilt of the head to one side has opposite effects on corresponding hair cells of the two utricular maculae. This concept is important in understanding how the central connections of the vestibular periphery mediate the interaction of inputs from the two sides of the head.

Front 267

The hair bundles extend out of the crista into a gelatinous mass, the cupula, that bridges the width of the ampulla, forming a viscous barrier through which endolymph cannot circulate. As a result, the relatively compliant cupula is distorted by

Back 267

The hair bundles extend out of the crista into a gelatinous mass, the cupula, that bridges the width of the ampulla, forming a viscous barrier through which endolymph cannot circulate. As a result, the relatively compliant cupula is distorted by movements of the endolymphatic fluid.

When the head turns in the plane of one of the semicircular canals, the inertia of the endolymph produces a force across the cupula, distending it away from the direction of head movement and causing a displacement of the hair bundles within the crista. In contrast, linear accelerations of the head produce equal forces on the two sides of the cupula, so the hair bundles are not displaced.

When the cupula moves in the appropriate direction, the entire population of hair cells is depolarized and activity in all of the innervating axons increases. When the cupula moves in the op-posite direction, the population is hyperpolarized and neuronal activity decreases.

Front 268

Each semicircular canal works in concert with the partner located on the other side of the head that has its hair cells aligned oppositely. There are three such pairs:

Back 268

Each semicircular canal works in concert with the partner located on the other side of the head that has its hair cells aligned oppositely. There are three such pairs: the two pairs of horizontal canals, and the superior canal on each side working with the posterior canal on the other side ( Figure 14.8C). Head rotation deforms the cupula in opposing directions for the two partners, resulting in opposite changes in their firing rates. Thus, the orientation of the horizontal canals makes them selectively sensitive to rotation in the horizontal plane. More specifically, the hair cells in the canal toward which the head is turning are depolarized, while those on the other side are hyperpolarized.

Front 269

The macula, which consists of hair cells and associated supporting cells. Overlying the hair cells and their hair bundles is

Back 269

The macula, which consists of hair cells and associated supporting cells. Overlying the hair cells and their hair bundles is a gelatinous layer; above this layer is a fibrous structure, the oto-lithic membrane, in which are embedded crystals of calcium carbonate called otoconia. The crystals give the otolith organs their name ( otolith is Greek for “ ear stones”). The otoconia make the otolithic membrane heavier than the structures and fluids surrounding it; thus, when the head tilts, gravity causes the membrane to shift relative to the sensory epithelium. The resulting shearing motion between the otolithic membrane and the macula displaces the hair bundles, which are embedded in the lower, gelatinous surface of the membrane. This displacement of the hair bundles generates a receptor potential in the hair cells.

Front 270

The vestibular system contributes to rapid automatic behaviors, such as reflexive eye movements that stabilize gaze and rapid postural adjustments to maintain balance, and also to higher order processes that are important to our sense of spatial orientation and self- motion. The organization of the central vestibular pathways reflects this multi-functional role; these pathways also display two features that distinguish them from the somatosensory, auditory and visual pathways.

Back 270

The vestibular system contributes to rapid automatic behaviors, such as reflexive eye movements that stabilize gaze and rapid postural adjustments to maintain balance, and also to higher order processes that are important to our sense of spatial orientation and self- motion. The organization of the central vestibular pathways reflects this multi-functional role; these pathways also display two features that distinguish them from the somatosensory, auditory and visual pathways. First, central vestibular processing is inherently multisensory, because many neurons in the vestibular nuclei— the earliest point in central vestibular processing— receive visual input. Second, many neurons in the vestibular nuclei function by synapsing on motor neurons/interneurons in addition to giving rise to ascending sensory projections, providing a very short- latency sensorimotor arc that can drive extremely rapid (~ 5 ms) compensatory eye and head movements in response to vestibular stimulation.

Front 271

Motion sickness—nausea, headache, anxiety, and vomiting sometimes experienced in moving vehicles—may be caused by

Back 271

Motion sickness—nausea, headache, anxiety, and vomiting sometimes experienced in moving vehicles—may be caused by a conflict between different types of sensory information or by postural instability. For example, when one reads in a car moving at a constant speed, information in central vision and from the vestibular apparatus indicates that one is not moving, yet peripheral vision is reporting movement. Seasickness may be caused by a conflict between visual and vestibular information.

Front 272

The vestibulocerebellum is the section of the cerebellum that receives vestibular information and influences postural muscles and eye motions. It adjusts the gain of responses to head movement via connections with the

Back 272

The vestibulocerebellum is the section of the cerebellum that receives vestibular information and influences postural muscles and eye motions. It adjusts the gain of responses to head movement via connections with the vestibular apparatus, vestibular nuclei, spinal cord, and inferior olive. Thus the magnitude of the reflex responses to changes in position and movement (of the head, body, or external objects) depends on VC processing of vestibular and visual information.

Front 273

For example, when maintaining visual fixation on a target while turning the head, the eyes

Back 273

For example, when maintaining visual fixation on a target while turning the head, the eyes move precisely opposite the direction of head movement. The gain of the response (the ratio of head movement to eye movement) is 1. The VC is vital for adaptation to vestibular disorders and to alterations in the postural and balance systems.

Front 274

Postural adjustments are achieved by reciprocal connections between the vestibular nuclei and the

Back 274

Postural adjustments are achieved by reciprocal connections between the vestibular nuclei and the spinal cord, reticular formation, superior colliculus, nucleus of cranial nerve XI, vestibular cerebral cortex, and the cerebellum. The lateral vestibulospinal tract, which originates in the lateral vestibular nucleus, is the primary tract for vestibular influence on lower motor neurons to postural muscles in the limbs and trunk. The medial vestibulospinal tract, via projections to the cervical spinal cord, conveys signals that adjust head position to upright according to information signals from the vestibular apparatus. The vestibular nuclei are linked with areas that affect signals in the corticospinal and reticulospinal tracts. By these connections, the vestibular nuclei strongly influence the posture of the head and body.

Front 275

The vestibulo- ocular reflex provides an important means of assessing the function of the vestibular, abducens, and oculomotor nerves and connections between their associated cell bodies in the brainstem.

When the head is rotated in the horizontal plane, the vestibular afferents on the side toward the turning motion increase their firing rate, while the afferents on the opposite side decrease their firing rate. The net difference in firing rates then leads to

Back 275

The vestibulo- ocular reflex provides an important means of assessing the function of the vestibular, abducens, and oculomotor nerves and connections between their associated cell bodies in the brainstem.

When the head is rotated in the horizontal plane, the vestibular afferents on the side toward the turning motion increase their firing rate, while the afferents on the opposite side decrease their firing rate. The net difference in firing rates then leads to slow movements of the eyes counter to the turning motion; in a conscious person with normal vestibular function, a fast saccade resets the eye position when the eye reaches its far excursion. This process is referred to as physiological nystagmus, which means “ nodding” or oscillatory movements of the eyes ( Figure B1).

Front 276

Pathologic spontaneous nystagmus can occur if there is unilateral damage to the vestibular system. In this case, the silencing of output from the damaged side results in

Back 276

Pathologic spontaneous nystagmus can occur if there is unilateral damage to the vestibular system. In this case, the silencing of output from the damaged side results in an abnormal difference in firing rate between the two sides. This difference causes nystagmus even though no head movements are being made.

Front 277

Sounds gathered by the external ear are airborne; how-ever, the environment within the inner ear, where the sound- induced vibrations are converted to neural impulses, is aqueous.

The major function of the middle ear is to

Back 277

Sounds gathered by the external ear are airborne; how-ever, the environment within the inner ear, where the sound- induced vibrations are converted to neural impulses, is aqueous.

The major function of the middle ear is to match relatively low- impedance airborne sounds to the higher-impedance fluid of the inner ear. Normally, when sound waves travel from a low- impedance medium such as air to a much higher- impedance medium such as water, almost all ( more than 99.9%) of the acous-tical energy bounces back. The middle ear overcomes this problem and ensures transmission of the sound energy across the air– fluid boundary by boosting the pressure measured at the tympanic membrane almost 200- fold by the time it reaches the inner ear.

Front 278

Two mechanical processes occur within the middle ear to achieve this transition. The first is achieved by focusing the force impinging on the relatively large- diameter tympanic membrane onto the much smaller- diameter oval window, the site where the bones of the middle ear contact the inner ear
The second process relies on

Back 278

The second process relies on the mechanical advantage gained by the lever action of the three small, interconnected middle ear bones, or ossicles, which connect the tympanic membrane to the oval window.
Conductive hearing losses, which involve damage to the external or middle ear, lower the efficiency sound energy is transferred to the inner ear and can be partially overcome by artificially boosting sound pressure levels with an external hearing aid.

Front 279

Actions of the medial longitudinal fasiculus

Back 279

Bilateral connections with the extraoccular nuclei (CN III, IV, & VI) and superior colliculus, influencing head and eye movements

Front 280

Actions of the vestibulospinal tracts

Back 280

both medial and lateral, to motor neurons that influence posture

Front 281

Actions of the vestibulocolic pathway

Back 281

To the nucleus of the spinal accessory nerve (CN XI), influencing head position

Front 282

Actions of the vestibulothalamocortical

Back 282

Providing conscious awareness of head position and movement and input to the corticospinal tracts

Front 283

Actions of the vestibulocerebellar pathway

Back 283

To the vestibulocerebellum, which controls the magnitude of muscle responses to vestibular information (including the gain of the VOR)

Front 284

actions of the vestibuloreticular pathway

Back 284

To the reticular formation, influencing the reticulospinal tracts and autonomic centers for nausea and vomiting

Front 285

Within the cochlea, is the organ of Corti, the organ of hearing. The organ of Corti is composed of

Back 285

Within the cochlea, is the organ of Corti, the organ of hearing. The organ of Corti is composed of receptor cells (hair cells), supporting cells, a tectorial membrane, and the terminals of the cochlear branch of cranial nerve VIII . The tops of the hairs that project from hair cells are embedded in the overlying tectorial membrane.

Front 286

Sensorineural hearing loss usually is due to congenital or envi-ronmental insults that lead to hair cell death or damage to the auditory nerve. As hair cells are relatively few in number and do not regenerate in humans, their depletion leads to a diminished ability to detect sounds. The treatment of profound sensorineural hearing loss is more complicated and invasive; conventional hearing aids are useless, because

Back 286

Sensorineural hearing loss usually is due to congenital or envi-ronmental insults that lead to hair cell death or damage to the auditory nerve. As hair cells are relatively few in number and do not regenerate in humans, their depletion leads to a diminished ability to detect sounds. The treatment of profound sensorineural hearing loss is more complicated and invasive; conventional hearing aids are useless, because no amount of mechanical amplification can compensate for the inability to generate or convey a neural impulse from the cochlea. However, if the auditory nerve is intact, cochlear implants can partially restore hearing. The implant consists of a peripherally mounted microphone and digital signal processor that transforms a sound into its spectral components.

Front 287

The points responding to high frequencies are at the ___ of the basilar membrane where it is ____, and the points responding to low frequencies are at the ____, giving rise to a topographical mapping of frequency ( i.e., tonotopy).

The traveling wave initiates sensory transduction by

Because the basilar membrane and the overlying tectorial membrane are anchored at _______, the vertical component of the traveling wave causes a _____ motion between these two membranes.

Back 287

The points responding to high frequencies are at the base of the basilar membrane where it is stiffer, and the points responding to low frequencies are at the apex, giving rise to a topographical mapping of frequency ( i.e., tonotopy).

The traveling wave initiates sensory transduction by moving the sensory hair cells that sit on the basilar mem-brane.
Because the basilar membrane and the overlying tectorial membrane are anchored at different positions, the vertical component of the traveling wave causes a shearing motion between these two membranes.

Front 288

The tonotopic organization of the cochlea is retained at all levels of the central auditory system. Projections from the cochlea travel via the ____ ___ to the cochlear nucleus. From the cochlear nuclei, auditory information is transmitted to three structures:

Back 288

The tonotopic organization of the cochlea is retained at all levels of the central auditory system. Projections from the cochlea travel via the auditory nerve to the cochlear nucleus. From the cochlear nuclei, auditory information is transmitted to three structures:

Reticular formation: connections here account for the activating effect of sounds on the entire central nervous system. For example, loud sounds can rouse a person from sleep.
Inferior colliculus (directly and via the superior olive) integrates auditory information from both ears to detect the location of sounds.
When the location information is conveyed to the superior colliculus, neural activity in the superior colliculus elicits movement of the eyes and face toward the sound.
Medial geniculate body (via the inferior colliculus) is the thalamic relay nucleus for sound to the primary auditory cortex for conscious awareness.

Front 289

Three cortical areas are dedicated to processing auditory information:

Back 289

Three cortical areas are dedicated to processing auditory information. A1: The primary auditory cortex is the site of conscious awareness of the intensity of sounds. A2: An adjacent cortical area, the secondary auditory cortex, compares sounds with memories of other sounds, then categorizes the sounds as language, music, or noise.
A3: Comprehension of spoken language occurs in yet another cortical area, called Wernicke's area.

Front 290

COMMUNICATION: “People use both language and nonverbal methods to communicate. In approximately 95% of adults, the cortical areas responsible for ______ _____ and _____ _____ are found in the left.

The distinction between language, a communication system based on symbols, and speech, the verbal output, is clinically important because different regions of the brain are responsible for each function.

Comprehension of spoken language occurs in _____'s area, a subregion of the left parietotemporal cortex. ______'s area, in the left frontal lobe, provides instructions for language output. These instructions consist of

Back 290

COMMUNICATION: “People use both language and nonverbal methods to communicate. In approximately 95% of adults, the cortical areas responsible for understanding language and producing speech are found in the left.

The distinction between language, a communication system based on symbols, and speech, the verbal output, is clinically important because different regions of the brain are responsible for each function.

Comprehension of spoken language occurs in Wernicke's area, a subregion of the left parietotemporal cortex. Broca's area, in the left frontal lobe, provides instructions for language output. These instructions consist of planning the movements to produce speech and providing grammatical function words, such as the articles a, an, and the. The contributions of the cortical and subcortical areas involved in normal conversation are shown in the figure.”

Front 291

Given that the right hemisphere typically does not process language, what do the contralateral areas corresponding to Wernicke's and Broca's areas contribute?

Back 291

Given that the right hemisphere typically does not process language, what do the contralateral areas corresponding to Wernicke's and Broca's areas contribute? In most people, activity in these areas of the right hemisphere is associated with nonverbal communication. Gestures, facial expressions, tone of voice, and posture convey meanings in addition to a verbal message. In the right hemisphere, the area corresponding to Wernicke's area is vital for interpreting nonverbal signals from other people. The right hemisphere area corresponding to Broca's area provides instructions for producing nonverbal communication, including emotional gestures and intonation of speech.

Front 292

RELATIONSHIP BETWEEN VERBAL AND WRITTEN COMMUNICATION: In contrast to the auditory neural networks used during conversation, reading requires...
Writing requires...

Back 292

RELATIONSHIP BETWEEN VERBAL AND WRITTEN COMMUNICATION: In contrast to the auditory neural networks used during conversation, reading requires intact vision, secondary visual areas for visual recognition of written symbols, and connections with an intact Wernicke's area for interpreting the symbols. Writing requires motor control of the hand in addition to connections with Wernicke's and Broca's areas. Broca's area provides the grammatical relationship between words when writing, and Wernicke's area provides formulation of language.

Front 293

Disorders of language can affect spoken language (_____), comprehension of written language (_____), and/or the ability to write (_____). Because _____ has the most severe impact on communication during treatment, the following discussion focuses on ____. Common types of _____ are Broca's, Wernicke's, conduction, and global.

Back 293

Disorders of language can affect spoken language (aphasia), comprehension of written language (alexia), and/or the ability to write (agraphia). Because aphasia has the most severe impact on communication during treatment, the following discussion focuses on aphasia. Common types of aphasia are Broca's, Wernicke's, conduction, and global.

Front 294

Broca's aphasia is defined as...

People with Broca's aphasia may...

Back 294

Broca's aphasia is defined as difficulty expressing oneself using language. The ability to understand language except grammatical function words (prepositions, pronouns, conjunctions) and an ability to control the muscles used in speech for other purposes (swallowing, chewing) are not affected. People with Broca's aphasia may not produce any language output, or they may be able to generate habitual phrases, such as “Hello. How are you?” or make brief meaningful statements, and may be able to produce emotional speech (obscenities, curses) when upset. People with Broca's aphasia usually are aware of their language difficulties and are frustrated by their inability to produce normal language. Usually writing is as impaired as speaking. The ability to understand spoken language except grammatical function words and to read is spared. Motor, expressive, and nonfluent types of aphasia are synonymous with Broca's aphasia.

Front 295

In Wernicke's aphasia, _____ is impaired. People with Wernicke's aphasia easily produce ____ but the output is meaningless. For a person with Wernicke's aphasia, listening to other people speak is...

Because the ability to _____ language is impaired, people with Wernicke's aphasia have...

Back 295

language comprehension is impaired. People with Wernicke's aphasia easily produce spoken sounds, but the output is meaningless. An example of a is “Wishrab lamislar blagg.” For a person with Wernicke's aphasia, listening to other people is equally meaningless, despite the ability to hear normally. The inability to produce & understand language may be analogous to when a person encounters an unknown foreign language. Wernicke's aphasia also interferes with the ability to comprehend & produce symbolic movements, as in sign language. Because the ability to comprehend language is impaired, people with Wernicke's aphasia have alexia (inability to read), inability to write meaningful words, & paraphrasia. Paraphrasia is the use of unintended words or phrases. Paraphrasia ranges from word substitution to the use of nonsensical, unrecognizable words. An example of word substitution is “captain of the school” instead of “principal.” Unlike people w/ Broca's, people w/ W's often appear unaware

Front 296

Synonyms for Wernicke's aphasia include

Back 296

Synonyms for Wernicke's aphasia include receptive, sensory, and fluent aphasia, although language output is also abnormal.

Front 297

Damage to the right cortex in the area corresponding to Broca's area may cause...
If the area corresponding to Wernicke's is damaged on the right side, the person has difficulty

Back 297

Damage to the right cortex in the area corresponding to Broca's area may cause the person to speak in a monotone, to be unable to effectively communicate nonverbally, and to lack emotional facial expressions and gestures. These consequences are sometimes referred to as flat affect. If the area corresponding to Wernicke's is damaged on the right side, the person has difficulty understanding nonverbal communication. Thus the person may be unable to distinguish between hearing “Get out of here” spoken jokingly and “GET OUT OF HERE!” spoken in anger.