Neuroscience Block 3

Front 1

nuclear chain fibers

Back 1

type of muscle spindle fiber
nuclei aligned in a chain, signal static length of muscle

Front 2

static nuclear bag fiber

Back 2

type of muscle spindle fiber, nuclei aligned in bags, tell static length of muscle

Front 3

what are the specialized endings of group 1a afferents called?
what info do group 1a afferents provide?

Back 3

annulospiral
they tell both length and velocity

Front 4

dynamic nuclear bag fibers

Back 4

type of muscle spindle fiber, nuceli in bags, tells velocity of muscle length

Front 5

what info do group 2 afferents provide and what are the specialized endings called?

Back 5

length only; endings called flower spray

Front 6

what info does the golgi tendon organ tell? how is it arranged in relation to the muscle?

Back 6

tells the load or force being applied
arranged in series

Front 7

what do group 1b afferents innervate?

Back 7

golgi tendon organs

Front 8

how do golgi tendon organs signal force?

Back 8

golgi tendon organ stretches->collagen fibers squeeze->distortion of primary afferent->afferent depolarizes->AP fired->signals the amt of force

Front 9

rate code

Back 9

a principle that states that the more ap fired by a motor neuron the greater the force of the motor unit

Front 10

size principle

Back 10

states that small motor neurons will be recruited first before large motor neurons (bc large motor neurons have less resistance, req more current to go below threshold)

Front 11

What initiates the myotactic reflex

Back 11

muscle spindles; although the reflex is sometimes referred to as the deep tendon reflex

Front 12

what type of fibers are associated with myotactic reflex

Back 12

group 1a afferents (synapsing on DRG and then to alpha motor neurons in spinal cord)

Front 13

what initiates the autogenic inhibition reflex

Back 13

golgi tendon organ

Front 14

what type of fibers in autogenic inhibition reflex

Back 14

1b (synapse on DRG to 1b inhibiotry interneurons to alpha motor neurons (inhibiting them))

Front 15

disynaptic reflex

Back 15

a reflex that contains an interneuron b/w sensory afferent and motor neuron (e.g. the autogenic inhibition reflex)

Front 16

what does the autogenic inhibition reflex do?

Back 16

when a muscle is contracted, 1b afferents are activated that synapse on inhibitory interneurons to cause that same muscle to cease contraction by inhibiting the alpha motor neuron and it also innervates excitatory interneuron to activate the alpha motor neuron of the antagonist muscle

Front 17

what receptors cause the flexor reflex

Back 17

cutaneous receptors and pain receptors

Front 18

describe the pathway of flexor reflex

Back 18

group III afferents->enter spinal cord->innervate excitatory interneurons (sometimes at many different muscles)-->innervate alpha motor neurons [this reflex also innervates inhibitory interneurons to prevent the opposite muscles from contracting]

Front 19

what is a crossed extension reflex

Back 19

where a branch of afferents (in the case of flexor reflex they are group3 afferents)cross the midline int eh contralateral spinal cord to innervate muscles in the opposite limb (this would be used to help support body weight - i.e. you step on a tack with your right leg and lift it up and the left leg needs to stabilize)

Front 20

renshaw cell

Back 20

an interneuron that innervates and inhibits the very same motor neuron that cased it to fire

Front 21

corticospinal system

Back 21

descending pathway that controls motor neurons and interneurons in the spinal cord (contributes to modulation of spinal reflexes)

Front 22

corticobulbar system

Back 22

descending pathwy that controls brainstem nuclei that innervate cranial muscles

Front 23

what happens when there is damage to lowest level in the reflex hierarchy

Back 23

paralysis

Front 24

what happens when there is damage in higher levels of the relfex hierarchy?

Back 24

deficits in motor planning, initiation, coordination; mvmt still possible

Front 25

what is the flexor extensor rule

Back 25

motor neurons that innervate flexors are more posterior than motor neurons that innervate extensors

Front 26

proximal distal rule

Back 26

motor neurons that innervate distal muscles are more lateral than those motor neurons that innervate proximal muscles

Front 27

what are the 2 lateral descending motor pathways

Back 27

lateral corticospinal and rubrospinal

Front 28

what are the medial descending pathways

Back 28

vestibulopsinal, reticulospinal, tectospinal and anterior corticospinal

Front 29

what are the functions of the corticospinal tract

Back 29

voluntary mvmt and voluntary control of axial muscles
lateral - distal muscles
anterior - proximal, specifically digits

Front 30

what results from damage to corticospinal tracts

Back 30

permanent loss of fine control of extermities

Front 31

what are the functions of the rubrospinal tract

Back 31

an alternative for voluntary motor commands to the spinal cord; excites flexors and inhibits extensors; movement velocity; transmitting learned motor commands from cerebellum to musculature; imp for recovery of voluntary motor function after damage to corticospinal

Front 32

what does damage to the rubrospinal tract cause

Back 32

slowness in mvmt

Front 33

what are the functions of vestibulospinal tract?

Back 33

mediate postrula adjustments and head movments
lateral tract - excites antigravity muscles; compensates for tilt, mvmt
medial tract - neck muscles to stabilize head, coordinates head and eye mvmts

Front 34

functions of the reticulospinal tract

Back 34

alternative to corticospinal; regulate flexor response to noxious stimuli; controls orientation, stretching and maintaining complex posture; initiate locomotor circuits in spinal cord; involved in integrating sensory input to guide motor output

Front 35

what does lesion in reticulospinal tract cause

Back 35

cause harmless stimuli such as gentle touches to elicit a flexor reflex

Front 36

what are the functions of tectospinal tract

Back 36

involved in reflexive turning of the head to orient visual stimuli

Front 37

where are voluntary mvmts initiated

Back 37

cerebral corrtex

Front 38

what are the modulations of reflexes and what controls them?

Back 38

gain (strength) and sign (ext or flex); descend motor pathways regulate

Front 39

what do alpha motor neurons innervate

Back 39

extrafusal muscle fibers for force of contraction

Front 40

what do gamma motor neurons innervate?

Back 40

ends of intrafusal fibers for tautness of muscle spindels

Front 41

what is alpha gamma coactivation

Back 41

coordination of alpha-gamma motor commands by descending pathways

Front 42

gamma bias

Back 42

adjustment of muscle spindles (when a muscle stretches the muscle spindle stretches with it, so that it can sense any further stretch, etc)

Front 43

what tract does the coricorubral tract modulate

Back 43

rubrospinal

Front 44

what tract does the corticotectal tract modulate

Back 44

tectospinal

Front 45

what tract does the corticoreticular trac modulate

Back 45

reticulospinal

Front 46

what does the corticostraite tract innervate?

Back 46

caudate nucleus, putamen

Front 47

what are the components of the primary motor cortex?

Back 47

30% = pyramidal cells (giant betz cells);
30% = fibers from premotor cortex
30% = somatosensory cortex
10% = post parietal cortex

Front 48

what do you the neurons in the primary motor cortex encode

Back 48

parameters that define individual mvmts or simple mvmt sequences; specifically FORCE of movement, direction, extent and speed of mvmt

Front 49

motor-set neuron

Back 49

fires when person is preparing or getting set to make a mvmt

Front 50

mirror neurons

Back 50

respond to a particular action of the person, but also to sight or sound of another individual performing the same action

Front 51

what does the premotor cortex signal?

Back 51

preparation for mvmt; sensory aspects of mvmt, behavioral context; correct and incorrect actions; generally it selects the appropraite motor plans for voluntary mvmts

Front 52

what is the SMA involved in

Back 52

sequence of mvmts and the mental rehearsal of them; transformation of kinematic to dynamic information

Front 53

dynamics of movements

Back 53

amt of force necessary to make a mvmt

Front 54

kinematics of mvmts

Back 54

the distance and angeles that define a particular mvmt in space

Front 55

what cortices does the association cortex include?

Back 55

prefrontal and pos parietal

Front 56

what does association cortex control?

Back 56

processing spatial relationships

Front 57

what is apraxia

Back 57

inability to make complex, coordinated mvmts; selection of appropriate actions for particular behavior

Front 58

how does damage to prefrontal cortex present?

Back 58

patients make inappropirate decisions and cannot anticipate the consequences of their actions; have impulsive behavior

Front 59

what area of the brain is associated with parkinsons

Back 59

pars compacta

Front 60

where does the frontal lobe project

Back 60

caudate head and putamen

Front 61

occipital and parietal lobes project

Back 61

caudate body

Front 62

temporal lobe projects to

Back 62

caudate tail

Front 63

primary motor and somatosensory cortex projects to

Back 63

putamen

Front 64

what are the major output structures of the basal ganglia?

Back 64

the globus pallidus internal segment and substantia nigra pars reticulata

Front 65

are the connections from GPint and SNr inhibitory or excitatory

Back 65

GABAergic inhibitory

Front 66

where does the GPint project to? and via wihich fiber tracts

Back 66

VA and VL and DM of thalamus via the ansa lenticularis and lenticular fasciculus

Front 67

where does the SNr project to

Back 67

superior colliculus (eye mvmts)

Front 68

what does the striatopallidal pathway connect

Back 68

bw the stratium and globus pallidus

Front 69

what does the striatonigral pathway connect

Back 69

bw the striatum and the SNr

Front 70

what is the only purely excitatory pathway in the basal ganglia

Back 70

the pathway that the subthalamic nucleus makes onto GP and SNr

Front 71

describe the direct pathway

Back 71

ordinarily:
GPint inhibits thalamus
thalamus less likely to inhibit neocortex
when direct pathway on:
striatum INHIBITS GPint
GPint can no longer inhibit the thalamus
thalamus can excites the cortex

Front 72

describe the indirect pathway

Back 72

striatum INHIBITS GPext
GPext inhibits the subthalamic nucleus
subthalamic EXCITES GPint
GPint inhibits the thalamus
bc the subthalamus excites the inhibitory action of the GPint, the thalamus is further INHIBITED. therefore the indirect pathway inhibits motor cortex

Front 73

what receptors are associated with direct and indirect pathways

Back 73

direct - dopaminergic D1
indirect - dopaminergic D2

Front 74

what is the dual effect the neostrigatal pathway has on the direct and indirect pathways

Back 74

excites the direct and inhibits the indirect; net effect = excitatory to motor cortex

Front 75

what cortices are associated with cognitive functions in the basal ganglia

Back 75

prefrontal and limbic

Front 76

what are the major motor functions of the basal ganglia

Back 76

enabling practiced motor acts
gating the initiation of voluntary mvmts
learning rewards

Front 77

what pathway is dead in parkinsons

Back 77

neostriatal

Front 78

what pathway is dead in huntingtons

Back 78

indirect