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Maddy - Neuro II - tracks > Anatomy - Motor Tracts > Flashcards

Anatomy - Motor Tracts Flashcards

1
Q

where are upper motor neurons located and where do their axons travel

  • what do they synapse with
A

located in cerebral cortex or brain stem

  • axons travel in descending tracts
  • synapse with lower motor neurons and/or interneurons of the spinal cord
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2
Q

what tracts involve upper motor neurons

A

corticospinal tract

corticobulbar tract (corticonuclear)

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3
Q

where are the cell bodies of lower motor neurons and where do they synapse

A

cell bodies in spinal cord or brain stem

  • synapse with skeletal muscle fibers
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4
Q

compare alpha and gamma motor neurons

A

alpha: large cell bodies, large myelinated axons, project to extrafusal skeletal muscle

gamma: medium sized, myelinated, project to intrafusal fibers of muscle spindle

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5
Q

what type neurons are peripheral and cranial nerves

A

lower motor neurons

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6
Q

describe the pathway of the lateral corticospinal tract

A

cell bodies arise in cortex –> descend through posterior limb of internal capsule –> cerebral peduncles –> anterior pons –> pyramids –> fibers cross in lower medulla –> descends in lateral column of spinal cord –> synapses with lower motor neurons in spinal cord

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7
Q

what does the medial corticospinal tract (of the corticospinal tract) encompass

A

postural muscles (10% of fibers)

  • neck, shoulder, and trunk muscles
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8
Q

what does the lateral corticospinal tract (of the corticospinal tract) encompass

A

limb muscles, fractionation (90% of fibers)

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9
Q

what is the source of most of the neurons in the corticospinal tract

A

primary motor cortex

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10
Q

in what way (contralaterally/ipsilaterally) does the primary motor cortex control the body

A

contralaterally

(right side motor strip controls left side of body)

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11
Q

compare lateral and medial corticospinal tracts

A

the medial (anterior) corticospinal tract remains ipsilateral throughout its tract

  • lateral tract becomes contralateral in the pyramids before descending into spinal cord
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12
Q

arterial supply to trunk/leg region of cortex

arterial supply to hand region of cortex

A

anterior cerebral a.

middle cerebral a.

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13
Q

blood supply to internal capsule

A

lenticulostriate arteries (posterior limb)

anterior choroidal artery

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14
Q

what artery supplies the midbrain where the corticospinal tract passes

A

posterior cerebral a.

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15
Q

what artery supplies the pons where the corticospinal tract passes through

A

paramedian branches of basilar a.

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16
Q

what artery supplies the medulla where the corticospinal tract passes through

A

sulcal branches of anterior spinal a.

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17
Q

arterial supply of corticospinal tract in the spinal cord

A

posterior and anterior spinal arteries

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18
Q

where do the axons of the corticobulbar tract arise from

A

ventral part of cortical area 4

(primary motor complex) (precentral gyrus)

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19
Q

describe the path of the corticobulbar tract

A

ventral part of cortical area 4 –> genu of internal capsule –> cerebral peduncles –> anterior pons –> pyramids –> stops in brainstem at specific motor nucleus

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20
Q

how do the axons of the corticobulbar tract travel

A

they cross to control the muscles on the contralateral side (except for CN 11 which stays ipsilateral and travels with median corticospinal tract)

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21
Q

how do the neurons of the corticobulbar tract affect the trigeminal nucleus in the pons

A

fibers split bilaterally to influence motor trigeminal nuclei

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22
Q

how do the neurons of the corticobulbar tract affect the facial nucleus in the pons

A

the facial motor nucleus that supplies the forehead is influenced bilaterally by the neurons of the corticobulbar tract

  • the contralateral lower side of the face is controlled contralaterally
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23
Q

how do the neurons of the corticobulbar tract affect the nucleus ambiguus (CN 9 and 10) in the medulla

A

it influences nucleus ambiguus bilaterally but the actual muscle influence seems to be controlled contralaterally

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24
Q

how do the neurons of the corticobulbar tract affect the spinal accessory nucleus in the spinal cord

A

ipsilaterally

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25
Q

how do the neurons of the corticobulbar tract affect the hypoglossal nucleus

A

contralaterally

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26
Q

where are lower motor neurons found

A

ventral horns

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27
Q

in the ventral horn, where are the lower motor neurons for axial muscles, limb muscles, extensor muscles, and flexor muscles

A

medial: axial muscles
lateral: limb muscles
posterior: flexor muscles
anterior: extensor muscles

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28
Q

what are the medial upper motor neuron tracts (4)

A

tectospinal

medial reticulospinal

lateral vestibulospinal

medial vestibulospinal

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29
Q

what are the lateral upper motor neuron tracts (2)

A

rubrospinal

lateral reticulospinal

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30
Q

describe the path of the lateral vestibulospinal tract

A

starts in superior/lateral vestibular nuclei in the pons –> stays ipsilateral to the spinal cord –> innervates lower motor neurons –> postural muscles and limb extensors (in relation to gravity)

**goes to all spinal cord levels**

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31
Q

describe the path of the medial vestibulospinal tract

A

starts in inferior vestibular nucleus in medulla –> descends bilaterally –> cervical and thoracic levels to innervate neck and shoulder muscle movement in relation to gravity

(don’t see this tract below T2/T3)

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32
Q

describe the path of the medial (pontine) reticulospinal tract

A

starts in pontine reticular formation in pons –> travels ipsilaterally to lower motor neurons in spinal cord–> innervates postural muscles and limb extensors (not in relation to gravity)

33
Q

describe the path of the lateral (medullary) reticulospinal tract

A

starts in medullary reticular formation in medulla –> stays mainly ipsilateral with some contralateral projections down the spinal cord –> facilitates flexor motor neurons and inhibits extensor motor neurons

34
Q

describe the path of the rubrospinal tract

A

starts in red nucleus of midbrain –> crosses to contralateral side –> travels down to spinal cord –> innervates upper limb flexors

35
Q

describe the path of the tectospinal tract

A

superior colliculus in midbrain –> upper spinal cord –> neck muscles (turning head to where eyes want to go)

36
Q

general function of corticospinal tract

A

fine motor control of hand

motor neuron recruitment to increase force

inhibition of postural reflexes

37
Q

general function of corticobulbar tract

A

control of muscles of face, chewing, speech, and swallowing

38
Q

general function of rubrospinal tract

A

facilitation of upper limb flexors

39
Q

general function of lateral vestibulospinal tract

A

facilitation of extension against gravity

40
Q

general function of medial vestibulospinal tract

A

coordination of head movements

41
Q

general function of pontine reticulospinal tract

A

facilitation of postural reflexes

42
Q

general function of medullary reticulospinal tract

A

inhibition of spinal segmental reflexes

43
Q

general function of tectospinal tract

A

coordination of head with eye movements

44
Q

sx of lower motor neuron lesion

A

flaccid paralysis

wasting or atrophy

hyporeflexia or areflexia

hypotonia

denervation hypersensitivity causing fasiculations

45
Q

what is upper motor neuron syndrome

A

a combination of the loss of the corticospinal tract and its collaterals sent to the indirect pathways

46
Q

sx of upper motor neuron lesion

A

loss of distal extremity strength (CST)

babinski’s (CST)

hypertonia

spasticity (clasp-knife phenomemon) - (CST or CBT)

rigidity

hyperreflexia

47
Q

what is the clasp knife phenomenon

A

spacsticity caused by loss of inhibitory commands from UMN

(muscle first resists, then relaxes)

48
Q

if a UMN lesion occurs above the lower medulla, where will the clinical signs be

A

contralateral

49
Q

if a UMN lesion occurs in the spinal cord, where will the clinical signs be?

A

ipsilateral

50
Q

compare spinal cord lesions between UMN and LMN

A

UMN signs will be below the level of the lesion

LMN signs will be at the level of the lesion

51
Q

what causes decorticate posture

A

UMN lesion above the level of the red nucleus

  • the rubrospinal tract will be intact (why you have flexion in UE) and reticulospinal and vestibulospinal (extension in LE)
52
Q

if you have damage to the corticospinal tract and lower motor neurons, which clinical sign will predominate?

A

lower motor neuron

(it’s the final common pathway for motor)

53
Q

pt comes in with thumb tucked under flexed fingers in fisted position, pronation of forearm, flexion at elbow, lower extremity in extension with foot inversion

  • what sign is this?
A

decorticate rigidity

54
Q

pt comes in with upper extremity in pronation and exntesion and lower extremity in extension

  • what sign is this?
A

decerebrate rigidity

55
Q

what causes decerebrate posture

A

lesion below red nucleus but above the reticulospinal and vestibulospinal nuclei

  • with lesion below red nucleus you lose the rubrospinal tract, so you lose ability to flex upper limb (UE will be in extension)
  • reticulospinal and vestibulospinal nuclei will be in tact (allows extension of limbs)
56
Q

if lesion occurs all along precentral gyrus, what tracts will it affect and where will the sx be

A

CST and CBT

  • contralateral side (including bottom half of face)
57
Q

sx of complete transection of the spinal cord

A

all sensation lost 1 or 2 levels below lesion

bladder and bowel control lost

spinal shock

UMN signs below the lesion

LMN signs at the lesion

58
Q

sx of hemisection of spinal cord (below medulla)

A

contralateral loss of pain and temperature

ipsilateral loss of discriminative touch and conscious proprioception

LMN signs on ipsilateral side at level of lesion

UMN signs on ipsilateral side below level of lesion

59
Q

what is Brown Sequard’s syndrome

A

the sx of a hemisection spinal cord

  • contralateral loss of pain and temp
  • ipsilateraly loss of disciminative touch and conscious proprioception
  • ipsilateral LMN signs at level of lesion
  • ipsilateral UMN signs below level of lesion
60
Q

what causes syringomyelia and what are its signs

A

formation of cysts within spinal cord in the central canal

  • shawl/cape pattern of pain and temp loss (from anterior white commissure being affected first)
  • atrophy/weakness of hand

(if ventral horn is affected –> LMN signs)

(if lateral corticospinal tract is affected –> UMN signs)

61
Q

what is anterior cord syndrome and what usually causes it

A

compression/damage to anterior part of spinal cord

causes: spinal cord infarction, intervertebral disc herniation, radiation myelopathy, occlusion of anterior spinal a.

62
Q

sx of anterior cord syndrome

A
  • ipsilateral UMN signs below level of lesion (from hitting lateral CST)
  • contralateral loss of pain and temp (from hitting lateral spinothalamic tract)
  • ipsilateral LMN signs (from hitting ventral horn)

(posterior columns intact and functional)

63
Q

what mechanism of injury usually causes central cord syndrome

A

cervical hyperextension

64
Q

what structures are hit in medial medullary syndrome

(“Dejerine Syndrome”)

A

pyramids

medial leminiscus

CN XII nucleus

65
Q

what are the sx of medial medullary syndrome (Dejerine Syndrome)

A

contralateral UMN signs (from hitting pyramids)

contralateral loss of proprioception (from hitting ML)

ipsilateral deviation of tongue towards lesion (from hitting hypoglossal nucleus)

66
Q

injury to what artery would cause medial medullary syndrome

A

anterior spinal a.

67
Q

what structures are hit in lateral medullary syndrome

(“Wallenberg’s Syndrome”)

A

anterolateral system (ALS tract)

spinal trigeminal nucleus and tract

nucleus ambiguus

vestibular nuclei

68
Q

what are the symptoms of lateral medullary syndrome

A

contralateral loss of pain and temp to body (from hitting ALS)

ipsilateral loss of pain and temp to face (from hitting trigeminal nucleus and tract)

hoarseness, difficulty swalloing, uvula deviation away, uneven elevation of pallate (from hitting nucleus ambiguus)

nystagmus, vertigo, ataxia (from hitting vestibular nuclei)

69
Q

injury to what artery would cause lateral medullary syndrome

A

PICA

70
Q

what causes central 7 palsy and what are the sx

A

lesion of corticobulbar tract involving CN 7

  • contralateral drooping of lower face
  • weak wrinkling of forehead bilaterally
71
Q

compare Bell’s and Central 7 palsy

A

Bell’s: ipsilateral flaccid paralysis of upper and lower face

central 7: contralateral dropping of lower face, weak wrinkling of forehead bilaterally

72
Q

what is Weber’s syndrome

A

lesion in the cerebral peduncle of the midbrain affecting CST, CBT, and neurons from CN III nucleus

73
Q

in the midbrain, if red nucleus is visible what other two structures should be at that level

A

superior colliculus

CN III

74
Q

if you are at the level of the inferior colliculus in the midbrain, what cranial nerve should also be at that level

A

CN IV

75
Q

sx of Weber’s syndrome

A

contralateral UMN sx (from hitting CST)

central 7 symptoms (from hitting CBT)

uvula deviates contralateral to lesion, tongue deviates ipsilateral (from hitting CBT)

down and out eyes (from hitting nerves leaving nucleus of CN III)

76
Q

sx of ALS

A

paresis (muscle weakness)

myoplastic hyperstiffness

hyperreflexia

babinski’s sign

atrophy

fasciculations

fibrillations

77
Q

how does amyotrophic lateral sclerosis (ALS) work

A

destroys somatic motor neurons

(UMNs and brainstem and spinal cord LMNs)

78
Q

what causes polyneuropathy

A

damage to sensory, motor, and autonomic neurons

79
Q

if pt presents with “stocking/glove” presentation, what disease process is this and how does it work

A

polyneuropathy

  • dying-back of imparied axonal transport
  • demyelizaiton may also contribute

Maddy - Neuro II - tracks (16 decks)

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