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Anatomy > descending motor systems > Flashcards

descending motor systems Flashcards

1
Q

where do peripheral neuropathies occur

A

axon

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2
Q

where do diseases of neuromuscularr transmissions occur

A

neuromuscular juntion

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3
Q

where do myopathies occur

A

muscle fibers (disease of)

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4
Q

the lower motor neurons innervate?

A

started muscle; directly signal muscle to contract. only way movement can be initiated

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5
Q

types of lower motor neurons

A

Alpha motor neurons: innervate extrafusal muscle fibers. INITIATE movement and contract muscles

Gamma motor neurons: intrafusal muscle fibers. REGULATE movement

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6
Q

what do LMN lesions cause

A

Atonia (abnormal relaxation of muscle), areflexia (loss of reflex), flaccid paralysis, fasciculations (spont. muscle contraction), and atrophy

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7
Q

what do UMN lesions cause

A
  1. spastic paralysis: hypertonia (spastic rigidity) and hyperreflexia (overactive reflex)
  2. pathological reflexes:
    BABINSKI SIGN- big toe dorsiflexion when side of heal is stroked
  3. mild disuse atrophy- because no regulation
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8
Q

are stretch reflexes increased or decreased with LMN lesion? UMN?

A

LMN: decreased
UMN: increased

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9
Q

is muscle tone increased or decreased with a LMN lesion? UMN

A

LMN: decreased
UMN: increased

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10
Q

is strength increased or decreased with LMN lesion? UMN?

A

decreased for both

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11
Q

motor unit

A

1 motor neuron + all myofibers it innervates. can vary in size

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12
Q

largest myofiber unit

A

antigravity muscle up to 1000 myofibers/unit

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13
Q

where are motor neurons located in the spinal cord

A

anterior horn (ventral)

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14
Q

Neurons controlling axial muscles are ____ to those controlling distal muscles

A

medial

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15
Q

Neurons controlling flexors are located ____ to the extensor groups

A

posterior

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16
Q 
type I dark muscle fibers
Action
Lipids
Glycogen
Ultrastructure
Physiology
Protoype
A 
action: sustained force weight bearing. long contractions
Lipids: abundant
glycogen: scant
ultrastructure: many mitochondria
Physiology: slow twitch
Prototype: turkey leg
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17
Q 
Type II white muscle fibers Action
Lipids
Glycogen
Ultrastructure
Physiology
Protoype
A 
A: sudden movements, purposeful motion. short
L: Scant
G: Abundant
U: few mitochondria
P: Fast twitch
Pro: turkey breast
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18
Q

how many muscle fiber types can be contained in one motor unit

A

just one; no mixing

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19
Q

does it take more motor units to jump or stand?

A

jump

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20
Q

why is the cortex hierarchical

A

because it decides what movements should occur

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21
Q

functions of premotor cortex

A

plans and tells motor cortex and then the LMN what to do.
plans movements in response to external cues

control of proximal and axial musculature (trunk, shoulder hip)

may assemble empathetic facial movements

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22
Q

motor control is in ____ arrangment

A

parallel

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23
Q

the basal ganglia and cerebellum influence output to cord and brainstem but have no direct effect on ___?

A

Lower motor nouns, most go to the motor and premotor cortices

24
Q

the ____ and the _____ and ____ are all vital in planning and monitoring movements

A

basal ganglia, cerebellum, and association cortex

25
Q

damage to the BG, cerebellum and association cortex causes

A

involuntary movement, gncoordingation, difficulty initiating movement but NOT weakness

26
Q

descending motor pathways mostly terminate or synapse on

A

internerons in the spinal cord but some directly synapse with lower/primary motor neuron (hand and CST)

27
Q

what are the descending motor pathways

A

corticospinal tract, corticobulbar tract, ccorticopontine tract

28
Q

another name for corticospinal tract

A

pyramidal tract. cortex to spine

29
Q

the primary motor cortex is referred to as area?

A

area 4 (40% fibers)

30
Q

function of primary motor cortex

A

execution of CONTRALATERAL voluntary movements and control of FINE DIGITAL movements

31
Q

the spinal cord motor neurons to the hand have ____ terminations

A

monosynaptic

32
Q

lesions to the primary motor cortex can lead to paralysis of

A

ctonralateral muscles

33
Q

premotor cortex is referred to as area?

A

area 6. on lateral aspect of cerebrum

34
Q

premotor cortex fibers project to

A

the primary motor are and reticular formation. and some fibers project to all spinal cord levels

35
Q

lesions in the premotor cortex cause?

A

moderate weakness of contralateral proximal muscles and loss of ability to associate learned hand movements to verbal or visual cues

36
Q

function of supplementary motor cortex

A

plans movements while thinking.

  1. assembles new sequence (playing new music)
  2. assembles previously learned sequence (music scale)
  3. imagines movmeents
37
Q

the supplementary motor cortex project into the

A

premotor and primary motor cortex areas

38
Q

what modulates sensory signals

A

somatosensory cortex and the superior parietal lobule (projects to sensory areas of the brainstem and spinal cord)

39
Q

why is the corticospinal tract a complex tract

A

it has multiple origins and destinations

40
Q

collaterals of the corticospinal tract project to

A

basal ganglia, thalamus, reticular formation, various sensory nuclei (dorsal column nuclei), posterior and intermediate horns of the spinal cord

41
Q

what is the only thing lost permanently if you cut the corticospinal tract?

A

fine finger movement because it synapses directly onto the LMN

42
Q

why are some abilities regained after you cut the corticospinal tract?

A

because not all movement is dependent on this tract, we have parallel tracts

43
Q

what is it called when coritcopsinal tract fibers cross the midline

A

pyramidal decussation

44
Q

the corticospinal tract originates in the

A

cerebral cortex, pre central gyrus and nearby areas

45
Q

what three areas does the corticospinal tract descend thru before decussation

A

cerebral peduncle, basis pontis, and medullary pyramid

46
Q

where does the coricospical tract (CST) decussate

A

spinomedullary junction

47
Q

where does the corticospinal tract synapse

A

on either cell bodies in the anterior horn or interneurons

48
Q

amount of uncrossed and crossed fibers in the CST

A

lateral- 80% cross in medulla and descend in LATERAL FUNICULUS

uncrossed- 10%

Anterior- 10% uncrossed and descend in the ANTERIOR FUNICULUS

49
Q

function of the Vestibulospinal tract

A

control of axial musculature- balance, mediate postural adjustments, antigravity reflex, cat reflexes

50
Q

function of the rubrospinal tract

A

control of shoulder and proximal arm musculature

51
Q

function of the reticulospinal tract

A

control axial musculature- walking rhythmic motion

52
Q

function of the tectospinal tract

A

head turning reflexes in response to visual stimuli

53
Q

origin of vestibular spinal tract

A

vestibular nuclei in ons

54
Q

where do the vestibulospinal tracts receive input from

A

vestibular system and cerebellum

55
Q

facilitates antigravity muscles

A

vestibulospinal tract

56
Q

origin of rubrospinal tract

A

red nucleus

57
Q

what are the two reticultospinal tracts

A

Medial: pons; ipsilateral descends near MLF in anterior funicular

lateral: medulla, descends bilaterally in lateral funiculus

Anatomy (12 decks)

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