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neuroanatomy > Motor Pathways > Flashcards

Motor Pathways Flashcards

1
Q

what are the CNS components that control movement?

A

basal ganglia, cortical motor areas, thalamus, brainstem, cerebellum

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2
Q

what do upper motor neurons do?

A

carry motor outputs from cerebrum/brainstem to LMN

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3
Q

what are lower motor neurons? what do they do?

A

cell bodies in brainstem or spinal cord
innervate muscles in the periphery

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4
Q

alpha motor neurons

A

large cell bodies
axons innervate skeletal muscle

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5
Q

gamma motor neurons

A

smaller axon fiber diameter
innervate muscle spindles to help control stretch reflexes

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6
Q

what will a lower motor neuron lesion cause?

A

muscle weakness and atrophy
fasciculations (twitching)
decreased tone
hyporeflexia

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7
Q

what will an upper motor neuron lesion cause?

A

muscle weakness, increased tone, hyperreflexia, abnormal reflexes or signs

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8
Q

how might acute UMN lesions present initially?

A

flaccid paralysis, decreased tone, hyporeflexia

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9
Q

motor pathways with cortical origins

A

lateral and ventral corticospinal, corticobulbar

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10
Q

motor pathways with brainstem origin

A

rubrospinal, vestibulospinal, tectospinal, reticulospinal

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11
Q

which tracts lie laterally in the spinal cord? what do they control?

A

lateral corticospinal, rubrospinal, corticobulbar*
appendicular muscles

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12
Q

which tracts lie medially in the spinal cord? what do they control?

A

ventral corticospinal, vestibulospinal, tectospinal, reticulospinal
axial/girdle postural muscles

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13
Q

why do medial pathways have a bilateral influence?

A

although they descend ipsilaterally, they synapse on interneurons in the intermediate zone as well as LMNs in the ventral horn

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14
Q

what movements occur due to the lateral corticospinal tract

A

rapid, dextrous movements at individual joints

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15
Q

where do most fibers originate in the lateral corticospinal tract?

A

precentral gyrus, primary motor cortex

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16
Q

what are other fiber origins for the lateral corticospinal tract?

A

premotor, supplementary motor, or parietal lobe

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17
Q

where are all the cell bodies of the lateral corticospinal tract?

A

cortical layer 5

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18
Q

lateral cortico spinal tract pathway

A

primary motor cortex
through posterior limb of internal capsule as corona radiata
middle 1/3 of crus cerebra
ventral pons
pyramids
axons cross in the pyramidal decussation
descend in lateral funiculus of spinal cord
synapse of LMN cell bodies in ventral horn

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19
Q

what movements occur due to the corticobulbar tract?

A

movement of facial, tongue, jaw, laryngeal, and pharyngeal muscles

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20
Q

where are cell bodies of the corticobulbar tract located?

A

lateral aspect of pre central gyrus

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21
Q

corticobulbar tract pathway

A

lateral aspect of pre central gyrus
genu of internal capsule
projections to facial motor nucleus, trigeminal motor nucleus, nucleus ambiguous, and hypoglossal nucleus

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22
Q

what happens if you lesion the corticobulbar tract?

A

paralysis of the contralateral lower face

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23
Q

what happens if you lesion the facial motor nucleus?

A

paralysis of the ipsilateral whole face

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24
Q

where is the trigeminal motor nucleus located?

A

mid-pons
bilateral projections

25
Q

where is the nucleus ambiguus located?

A

rostral medulla
bilateral projections (pharyngeal/laryngeal muscles)

26
Q

where is the hypoglossal nucleus located?

A

rostral dorsal medulla
most often bilateral projections

27
Q

where is the spinal accessory nucleus located?

A

caudal medulla
non-symmetrical bilateral projections

28
Q

rubrospinal tract function

A

exact function is unclear, likely influences flexors of upper limbs

29
Q

rubrospinal tract pathway

A

cell bodies in red nucleus
axons decussate in midbrain immediately
dorsolateral aspect of pons and medulla
lateral funiculus of the spinal cords
ventral horn of cervical cord

30
Q

what does flexor posturing indicate?

A

the corticospinal tract is damaged above the red nucleus

31
Q

what does extensor posturing indicate?

A

brainstem damage below the red nucleus

32
Q

key traits of posturing

A

occur in a comatose patient
only see a response in the upper limbs
move in the direction of painful stimuli

33
Q

where does the ventral corticospinal tract project to?

A

only to cervical and upper thoracic spinal cord

34
Q

what movements occur due to the ventral corticospinal tract?

A

control of bilateral axial and girdle muscles

35
Q

ventral corticospinal tract pathway

A

axons originate in lateral cortical spinal tract and follow this pathway until pyramidal decussation
tract does NOT decussate, descends into ventral funiculus of cord
some axons cross in the spinal cord, synapse on LMN and interneurons

36
Q

what is the vestibulospinal tract important for?

A

maintaining balance and posture
receives input from vestibular organs

37
Q

where are cell bodies of the vestibulospinal tracts?

A

medial and lateral vestibular nuclei of medulla and pons

38
Q

lateral vestibulospinal tract pathway

A

ipsilaterally in ventral funiculus of sc
synapse in ventral horns on LMNs and intermotor neurons
(posture and balance)

39
Q

medial vestibulospinal tract pathway

A

descends bilaterally to superior cervical sc levels
(control head position related to eye position)

40
Q

tectospinal tract pathway

A

originates in neurons in deep layers of superior colliculus, decussates immediately
projects to cervical spinal segments

41
Q

what is the tectospinal tract important for?

A

partial control of neck, shoulder, and upper trunk muscles
roles in eye/head movement coordination

42
Q

reticulospinal tract pathway

A

originate in pontine/medullary reticular formation
descend in ventral funiculus
ipsilateral tract with bilateral motor control

43
Q

what is the reticulospinal tract important for?

A

influencing automatic movements like posture control and balance on uneven terrain

44
Q

what are segmental interneurons?

A

short axon that distributes branches ipsilaterally within a single spinal segment
synapse on MN or other interneurons

45
Q

segmental interneuron input

A

receives input from somatic sensory receptors for reflex control of movement

46
Q

what are commissural interneurons?

A

axons distribute bilaterally for movement coordination of both sides of the body

47
Q

what are propriospinal interneurons?

A

axons project for multiple spinal segments before synapsing on MNs
(upper-lower limb coordination)

48
Q

where is the supplementary motor area located? what is its role?

A

medial surface of cerebral hemisphere
specific role unknown

49
Q

where is the cingulate motor area located? what is its role?

A

medial surface, deep in cingulate sulcus
part of the limbic system

50
Q

where is the premotor cortex located?

A

lateral hemisphere, ventral to primary motor cortex

51
Q

what is the dorsal premotor cortex function?

A

helps control reaching

52
Q

what is the ventral premotor cortex function?

A

helps control grasping
contains mirror neurons that activate when watching others perform an action

53
Q

what occurs when there is damage to the premotor areas?

A

apraxia, motor planning disorders
loss of ability to produce learned purposeful movements

54
Q

what is needed in order to produce movement?

A

decision to move (limbic and prefrontal)
visual info (posterior parietal cortex)

55
Q

what is multiple sclerosis?

A

autoimmune inflammaotry disorder to the CNS myelin that affects UMNs
plaques of demyelination can appear and disappear on an MRI

56
Q

what is Guillain-Barré syndrome?

A

immune-mediated demyelination of peripheral nerves
typically onsets 1 to 2 weeks following a viral or bacterial illness

57
Q

Guillain-Barré presentation

A

ascending progressive weakness, areflexia, tingling paresthesia of hands and feet

58
Q

what is Amyotrophic Lateral Sclerosis?

A

gradual degeneration of upper and lower motor neurons

neuroanatomy (14 decks)

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