Neuro Exam 3 Spring 2011

Front 1

What is a lower motor neuron?

Back 1

synapses directly with skeletal muscle
includes: anterior horn neurons, CN motor neurons and includes the cell bodies and axons of these neurons

Front 2

What sx result from a lower motor neuron lesion?

Back 2

flaccid paralysis, hypotonia, hyporeflexia, atrophy, and fasciculations

Front 3

What is an upper motor neuron?

Back 3

synapse with other neurons, NOT muscles
-includes: corticospinal, corticonuclear neurons and includes the cell bodies and axons of these neurons

Front 4

What sx result from an upper motor neuron lesion?

Back 4

spastic paralysis, hypertonia, hyperreflexia, no immediate atrophy, (disuse atrophy may appear later)

Front 5

What kind of sx would we see if BOTH the upper and lower motor neurons were damaged?

Back 5

lower motor neuron signs appear

Front 6

Where are the flexor neurons located in the spinal cord gray matter? Extensors?

Back 6

in the posterior portion of the anterior horn
extensors-ant. region of ant. horn

Front 7

What are the 3 types of intrafusal fibers?

Back 7

1)static nuclear bag
2)dynamic nuclear bag
3)nuclear chain

Front 8

What is a muscle spindle?

Back 8

encapsulated intrafusal sk. mm. fibers interspersed with other sk. mm. fibers
-tethered to mm. tendons or neighboring extrafusal mm. fibers
-innervated by mechanoreceptive sensory fibers and gamma motor neurons
-3 types

Front 9

Describe the static nuclear bag fibers.

Back 9

nuclei clustered in central region of the cell
-contractile elements only at distal ends of fiber
-innervated by type Ia sensory neurons
-mechanoreceptors respond to change in mm. length
-excite alpha motor neurons to same muscle

Front 10

Describe dynamic nuclear bag fibers.

Back 10

same as the static nuclear bag fibers except that they respond to rate of change in muscle length

Front 11

Describe nuclear chain fibers.

Back 11

nuclei arranged in a single row
-contractile elements located only at distal ends of fiber
-innervated by type II sensory neurons
-mechanoreceptors respond to change in mm. length
-excite alpha motor neurons innervating same mm.

Front 12

Describe golgi tendon organs.

Back 12

located in myotendinous junctions
-mechanoreceptor that responds to change in mm/tendon tension
-activation threshold greater than that of mm. spindle
-innervated by type Ib sensory neurons that synapse on inhib. interneurons which then inhibit alpha motor neurons to same mm.

Front 13

Describe the sequence of events in the gamma loop starting with the activation of the gamma motor neuron.

Back 13

gamma motor neuron activation-->intrafusal mm. fibers contract-->Ia sensory neuron activity increases-->excitation of alpha motor neurons innervating same muscle-->extrafusal mm. fibers contract
-this is all critical for maintenance of normal stretch reflexes and mm. tone

Front 14

What is clonus?

Back 14

refers to repetitive alternating contractions of flexor and extensor muscles at a single joint due to hyperactive stretch reflexes

Front 15

Describe the tendon reflex.

Back 15

1a sensory neuron detects change in mm length when the tendon is "tapped" and increases its firing rate-->the 1a sensory neuron forms an excitatory synapse directly on the alpha motor neuron innervating the mm being stretched and that mm. contracts

Front 16

Describe the process of reciprocal inhibition.

Back 16

-occurs in conjunction with tendon reflex
-1a sensory neurons also synapse on 1a inhibitory interneurons-->those inhibitory neurons then synapse on alpha motor neurons that innervate a mm. antagonistic to the stretched mm. spindle

Front 17

What is autogenic inhibition?

Back 17

type 1b sensory neuron of GTO responds to an increase in mm/tendon tension by increasing its AP firing rate-->1b sensory neurons synapse on 1b inhibitory interneurons-->these neurons then inhibit the alpha motor neurons that innervate the mm. being contracted and mm. tension decreases

Front 18

Describe the withdrawal reflex.

Back 18

-a painful stimulus activates a cutaneous pain receptor-->a pain primary sensory neuron carries pain signal into the spinal cord-->those fibers then synapse on inhib. and excit. interneurons-->excitatory interneurons synapse on alpha motor neurons that innervate whatever mm. are required to withdraw from painful stimulus and inhib. interneurons inhibit alpha motor neurons that innervate mm. that would impede withdrawal from pain stimulus

Front 19

Describe the crossed extension reflex.

Back 19

occurs in conjuction with the withdrawal reflex
-pain sensory fibers synapse on interneurons that cross to C/L side of SC and synapse on excit. and inhib. interneurons-->excit. synapse on alpha motor neurons that generally excite C/L extensor mm. used to stabilize the body (if flexion was stim. on other side of body for withdraw reflex) and inhib. would inhibit the flexors on the C/L side

Front 20

Do the vestibular nuclei receive input from the cerebral cortex?

Back 20

no

Front 21

Where do the vestibular nuclei receive input from?

Back 21

cerebellar cortex-inhibitory
cerebellar nuclei-excitatory
CN VIII-excitatory

Front 22

Describe the pathway of the medial vestibulospinal tract.

Back 22

arises in the medial and inferior vestibular nuclei-->descends bilaterally as MLF-->reaches to lower cervical/upper thoracic levels of spinal cord-->influences extensor mm.

Front 23

Describe the pathway of the lateral vestibulospinal tract.

Back 23

arises in lateral vestibular nucleus-->descends predominately ipsilateral in the anterior portion of the ant. funiculus -->extends entire length of SC-->influences extensor muscles

Front 24

Describe the reticulospinal tracts in general.

Back 24

-two bundles of axons (pontine and medullary fibers)
-both are primarily ipsilateral
-extend throughout spinal cord
-influence extensors primarily

Front 25

Describe the pontine reticulospinal fibers.

Back 25

part of the reticulospinal system
-medial reticular formation
-fiber tract in medial position
-delivers excitatory influence

Front 26

Describe the medullary reticulospinal fibers.

Back 26

-part of the reticulospinal system
-medial reticular formation
-fiber tract in lateral position
-delivers inhibitory influence

Front 27

What input does the pontine reticulospinal tract receive?

Back 27

pain input (+) from ALS
cerebral cortical (+) input

Front 28

What input does the medullary reticulospinal system receive?

Back 28

cerebral cortex (+)

Front 29

Describe the pathway of the rubrospinal tract.

Back 29

originates in red nucleus-->axons cross in midbrain-->extends only to low cervical or upper thoracic levels-->has an excitatory influence on flexors of the upper limb

Front 30

What input does the rubrospinal tract receive?

Back 30

cerebral cortical input-(+)
cerebellar nuclear input (+)

Front 31

Describe the decorticate posture.

Back 31

upper limbs flexed, lower limbs extended
-lesion is rostral to red nucleus so rubrospinal tract is still intact and leads to flexion in upper limb

Front 32

Describe the decerebrate posture.

Back 32

all four limbs extended
-lesion is caudal to red nucleus and involves rubrospinal tract leading to extension in all limbs

Front 33

What does it signal if there is progression from decorticate to decerebrate posture?

Back 33

it signals that the lesion (hemorrhage) is descending into brainstem
-might involve CV and resp. systems in medulla and pt. may need resp. and CV support soon

Front 34

What is the corpus striatum (also called the dorsal basal nuclei)?

Back 34

caudate nucleus + putamen + globus pallidus

Front 35

What is the lenticular nucleus?

Back 35

putamen + globus pallidus

Front 36

What is the striatum?

Back 36

caudate nucleus + putamen

Front 37

What is the pallidum?

Back 37

globus pallidus

Front 38

What is the most significant structure in the ventral striatum?

Back 38

nucleus accumbens

Front 39

What is the most significant structure in the ventral pallidum?

Back 39

substantia innominata

Front 40

What makes up the basal nuclei?

Back 40

corpus striatum (dorsal basal nuclei) + ventral striatum and ventral pallidum (ventral basal nuclei)

Front 41

What is the primary function of the basal nuclei?

Back 41

control of learned stereotyped movements

Front 42

What is the main afferent connection (input) to the basal nuclei?

Back 42

cerebral cortex

Front 43

What is the main efferent connection (output) from the basal nuclei?

Back 43

VA/VL nuclei of thalamus

Front 44

Describe the neurons in the pars compacta.

Back 44

the pars compacta is the posterior portion of the substantia nigra
-it appears dark in unstained sections b/c it has numerous melanin-containing neuron cell bodies
-the neurons use dopamine as NT

Front 45

What do the lenticulostriate arteries supply?

Back 45

-it is a branch of the middle cerebral a.
post limb of internal capsule
globus pallidus
putamen
body of caudate nucleus

Front 46

What does the medial striate artery supply?

Back 46

head of the caudate nucleus

Front 47

What does the anterior choroidal artery supply?

Back 47

-branch of the internal carotid a.
supplies the tail of the caudate nucleus
optic tract
amygdala
hippocampus

Front 48

What is the striatal complex?

Back 48

caudate nucleus + putamen + nucleus accumbens

Front 49

Describe the connections of the striatal complex.

Back 49

afferent-from cerebral cortex and substantia nigra

efferent-to globus pallidus

Front 50

What are the 2 regions of the striatal complex?

Back 50

striosomes (patches)-AChE poor
matrix-AChE rich

-cholinergic interneurons are present

Front 51

What are medium spiny neurons?

Back 51

found in the striatal complex
-they are found in the patch and matrix compartments
-dendrites respect patch/matrix boundaries
-exhibit very little spontaneous firing
-NT is gaba

Front 52

What is the pallidal complex?

Back 52

globus pallidus + substantia innominata

Front 53

What are the connections of the pallidal complex?

Back 53

afferent-from striatum and subthalamic nucleus

efferent-to thalamus

Front 54

Describe the efferent neurons of the pallidal complex.

Back 54

exhibit high rate of spontaneous firing
-NT is GABA
-tonic inhibition of targets
-project to thalamus (thalamic fasciculus=lenticular fasciculus + ansa lenticularis)

Front 55

What do all circuits involving the basal nuclei include?

Back 55

cerebral cortex-->basal nuclei-->thalamus-->cerebral cortex

Front 56

Describe the indirect path for the motor loop involving the basal nuclei.

Back 56

it is inhibitory and decreases motor output, "the brake"

-the direct path does the opposite, it is excitatory and enhances motor output, "the accelerator"

Front 57

What are hypokinetic disorders?

Back 57

negative signs the patient wants to perform but cannot
-lesion of the striatum affects both the indirect and direct pathways

Front 58

What is akinesia?

Back 58

impairment of initiation of a movement
-due to disruption of planning and generating programmed movements

Front 59

What is bradykinesia?

Back 59

reduction in speed and force of a movement
-due to inappropriate activation of antagonist muscles

Front 60

What is a resting tremor?

Back 60

due to alteration of thalamic activity
-thalamus has an intrinsic oscillatory firing mechanism which when released from inhibitory control leads to resting tremors

Front 61

What are hyperkinetic disorders?

Back 61

involuntary movements
-these positive signs are actions the patient does not want to perform but cannot prevent
-lesion of the striatum affects indirect pathway only

Front 62

What is ballism?

Back 62

a type of hyerkinetic disorder in which there is rapid flinging movements of limbs esp. in upper extremity

Front 63

What is athetosis?

Back 63

a hyperkinetic disorder in which there is slow writhing movements of the distal limbs, more obvious in upper extremity

Front 64

Describe Parkinson disease.

Back 64

sx:akinesia, bradykinesia, resting tremor

-loss of dopaminergic input from the pars compacta of substantia nigra affects both direct and indirect pathways
-can be consequence of degenerative, vascular, or inflamm. disease
-etiology can be genetic, due to trauma, or unknown
-initial sx 45-65 yo

Front 65

Describe Huntington disease.

Back 65

sx:chorea with progressive dementia in late stage

-degeneration of medium spiny neurons in striatum for indirect pathway
-motor activity is released from inhibitory control of indirect pathway
-autosomal dominant disorder
-initial sx 35-40 yo

Front 66

Describe tardive dyskinesia.

Back 66

sx:involuntary chewing movements, smacking of lips and tongue

-hypersensitivity to dopamine and its agonists restricted to basal nuclei pathways for face caused by chronic tx with some meds

Front 67

What is hemiballismus?

Back 67

sx:ballism (esp. in upper limbs)

-caused by damage to C/L subthalamic nucleus

Front 68

Where do fibers in the inferior cerebellar peduncle project from/to?

Back 68

restiform body-afferent nerve fibers from spinal cord and medulla

juxtarestiform body-afferent/efferent nerve fibers from and to vestibular nuclei

Front 69

Where do fibers in the middle cerebellar peduncle go?

Back 69

afferent nerve fibers from pontine nuclei

Front 70

Where do fibers in the superior cerebellar peduncle go?

Back 70

mostly efferent nerve fibers from cerebellar nuclei to the VL/VA nuclei of thalamus and red nucleus of midbrain

Front 71

Which fibers synapse directly on purkinje cells in the cerebellum?

Back 71

climbing fibers

Front 72

WHere do mossy fibers synapse in the cerebellum?

Back 72

on granule cells in the granular layer

Front 73

Where do purkinje cells synapse in the cerebellum?

Back 73

on cerebellar nuclei

Front 74

Through which cerebellar peduncle do the climbing fibers enter the cerebellum?

Back 74

the ICP

Front 75

Where do climbing fibers originate?

Back 75

the inferior olivary nuclei (contralateral)

Front 76

Where do the climbing fibers synapse?

Back 76

in cerebellar nuclei and on purkinje cells
-each purkinje cell receives many synaptic contacts from one climbing fiber and that climbing fiber may synpase on several Purkinje cells

Front 77

What does the waveform look like as a result of climbing fiber excitation on Purkinje cells?

Back 77

a complex spike waveform

Front 78

Where do the mossy fibers originate?

Back 78

many locations including pontine nuclei (C/L), vestibular nuclei (I/L), and as the second order neurons of spinocerebellar pathways (I/L)

Front 79

Where do the mossy fibers enter the cerebellum?

Back 79

all 3 peduncles

Front 80

Where do mossy fibers synapse?

Back 80

on cerebellar nuclei and on granule cells

Front 81

What waveform results from excitation of the purkinje cells by mossy fibers?

Back 81

simple spike waveform

Front 82

Describe the pathway of the posterior spinocerebellar tract.

Back 82

transmits NC proprioception from lower limbs and trunk, regarding limb position and movement
-first order neuron central processes enter the spinal cord and ascend in the post. funiculus--> synapse in ipsilateral dorsal nucleus of Clarke (T1-L2)-->second order neuron axons ascend in the ipsilateral lateral funiculus (post. portion)-->they reach the cerebellum via restiform body of the ICP

Front 83

Describe the pathway of the cuneocerebellar tract.

Back 83

NC proprioception from the upper limb, regarding limb position and movement
-first order neuron central processes from C2-T4 ascend in the ipsilateral cuneate fasciculus-->synapse in the accessory cuneate nucleus of medulla-->second order neurons reach the cerebellum via the restiform body of the ICP

Front 84

Describe the pathway of the anterior spinocerebellar tract.

Back 84

NP proprioception from the lower limb, regarding spinal cord motor circuits (mostly groups of muscles)
-first order neuron central processes enter the spinal cord and synapse on spinal border cells from L3-L5 (ipsilateral)-->second order neuron axons cross midline in ant. white comm. and ascend in C/L lateral funiculus (ant. portion)-->second order neurons cross the midline again at the pons and reach the cerebellum via the SCP

Front 85

What are parallel fibers?

Back 85

axons of granule cells

Front 86

Describe the input/output of the fastigial nucleus in the cerebellum.

Back 86

-input from medial zone (vermis) and flocculonodular lobe
-efferents exit in juxtarestiform bodies primarily to vestibular nuclei and reticular formation BILATERALLY

Front 87

Describe the inputs/outputs of the globose and emboliform nuclei.

Back 87

-input from intermediate zone
-efferents exit in SCP primarily to contralateral red nucleus

Front 88

Describe the inputs/outputs of the dentate nucleus.

Back 88

-input from lateral zone
-efferents exit in SCP primarily to C/L thalamus (VL/VA nuclei)

Front 89

What cells in the cerebellum use GABA?

Back 89

Purkinje cells, basket cells, stellate cells, and golgi cells

Front 90

What cells in the cerebellum use aspartate?

Back 90

climbing fibers, cerebellar efferent fibers

Front 91

What cells in the cerebellum use glutamate?

Back 91

mossy fibers, granule cells, cerebellar efferent fibers

Front 92

Describe the trigeminocerebellar pathway.

Back 92

central processes of first order neurons with cell bodies in the mesencephalic nucleus form the mesencephalic tract of the trigeminal nerve
-NC proprioceptive information is transmitted to many locations consistent with the participation in coordination of oral motility patterns including mastication, speech, and swallowing
-some of these fibers pass through the SCP to the cerebellum

Front 93

What is the definition of a functional cerebellar module?

Back 93

a cerebellar cortical zone and its corresponding nucleus or nuclei and white matter

-within that module a row of purkinje cells is excited (by climbing and parallel fibers) while the flanking rows are inhibited (by basket and stellate cells) leading to adjacent groups of cerebellar nuclei cells being inhibited and not inhibited

Front 94

Describe the premotor cortex.

Back 94

contains complete somatotopic map of all muscles
-receives input from all parietal lobe areas that receive sensory input
-it "sets" the proper posture for limb prior to movement initiation
-neurons active before M1 cells-control proximal limb mm. to set the proper posture for the starting point of the desired movement
-limb movements are guided by some type of sensory input rather than memory guided experience

Front 95

What is the function of the supplementary motor cortex?

Back 95

-plans the sequence of muscle activation required to perform the movement
-contains somatotopic map of all mm.
-activates functional groups of mm. that act across multiple joints
-often controls movements requiring use of both hands
-movements are internally guided by prior training, memory, experience

Front 96

What is apraxia?

Back 96

hands can participate in some movements but not in others
-there is no true muscle paralysis, no hypertonia, and no hyperreflexia

Front 97

Describe the function of the parietal motor cortex.

Back 97

area 5-arm projection cells active only when reaching for a specific object

area 7-eye-hand coordination cells active when reaching for a visually identified target

-both formulate a plan for movement in 3D space

Front 98

Describe the function of the cingulate motor cortex.

Back 98

area 24 and 32
-two separate clusters of neurons, one in the superior bank, the other in inferior bank of cingulate sulcus, inferior to supplementary cortex
-controls movements that occur in an emotional context

Front 99

Where do corticospinal neurons terminate?

Back 99

-most terminate on interneurons that control the flexor motor neurons
-some synapse directly on motor neurons that control wrist and finger movements
-

Front 100

What are the functions of the corticospinal neurons?

Back 100

-excite flexor motor neurons (via interneurons) that control upper and lower limb mm., esp. those involved with rapid, precise movements of the fingers and wrist
-some fibers produce inhibition of antagonist mm. through inhib. interneuron
-some fibers inhibit or excite spinal reflex circuits through spinal interneurons

Front 101

What are the inputs of the vestibulocerebellar module?

Back 101

1)I/L vestibulocerebellar fibers (via Juxtarestiform body) that convey info. regarding the position of the body and head to the flocculonodular lobe

2)C/L olivocerebellar fibers (via restiform body)

3)C/L pontocerebellar fibers (via MCP)

Front 102

Where do Purkinje cells of the vestibulocerebellar module project to?

Back 102

the I/L vestibular nuclei (via jr body) and the I/L fastigial nucleus

Front 103

What are the functions of the vestibulocerebellar module?

Back 103

posture, balance, and equilibrium through flocculonodular lobe (and a portion of the medial zone), fastigial efferents, and vestibulosp. and reticulosp. tracts

-coordinated eye movements through flocculonodular lobe, fastigial efferents, and MLF

Front 104

What would happen if there was vestibulocerebellar dysfunctions (flocculonodular lobe syndrome)?

Back 104

truncal ataxia-unsteady lurching gait with tendency to fall, tremor of trunk or head, unable to walk heel-to-toe, wide-based stance
-deficits in pursuit eye movements
-nystagmus

Front 105

What are the functions of the spinocerebellar module?

Back 105

-control of axial musculature through medial cerebellar cortex, fastigial efferents, and vestibulospinal and reticulospinal tracts
-control of distal limb musculature through intermediate cerebellar cortex, globose, and emboliform efferents, and rubrospinal tract

Front 106

Describe spinocerebellar dysfunction (anterior lobe syndrome).

Back 106

-deficits similar to those from vestibulocerebellar module or from pontocerebellar module
-this is b/c the lesion begins in either the medial or lateral zone of the cerebellum and then progresses through the cerebellum

Front 107

Where do Purkinje cells of the lateral zone project to?

Back 107

the dentate nucleus

Front 108

What is the function of the pontocerebellar module?

Back 108

planning, initiation, and timing of precise dexterous movements of the extremities, particularly the arm, forearm, and hand through the lateral cerebellar cortex, dentate efferents, and corticospinal tract

Front 109

Describe pontocerebellar dysfunctions (posterior lobe syndrome).

Back 109

-damage involving only cerebellar cortex rarely results in permanent motor deficits
-damage involving cerebellar cortex and nuclei, or just nuclei results in a wide range of I/L motor problems

-appendicular ataxia-intention tremor, unsteady lurching gait, rebound phenomenon, dysmetria, dysdiadochokinesia, dysarthria, dyssynergia,hypotonia, nystagmus

Front 110

What is acute ataxia?

Back 110

often due to toxin ingestion (alcohol) or stroke

Front 111

What is chronic ataxia?

Back 111

often due to chronic toxin ingestion (alcohol, mercury, etc) brain metastases, MS, and many other medical disorders

Front 112

What type of lesion could cause truncal ataxia?

Back 112

a medial lesion I/L or B/L
-unsteady lurching gait, unable to walk heel to toe, wide based stance

Front 113

What type of lesion may cause appendicular ataxia?

Back 113

intermediate or lateral lesion of the cerebellum, I/L
-intention tremor, etc..