descending motor systems Flashcards by leslie scott

where do peripheral neuropathies occur

axon

How well did you know this?

Not at all

Perfectly

where do diseases of neuromuscularr transmissions occur

neuromuscular juntion

How well did you know this?

Not at all

Perfectly

where do myopathies occur

muscle fibers (disease of)

How well did you know this?

Not at all

Perfectly

the lower motor neurons innervate?

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

How well did you know this?

Not at all

Perfectly

types of lower motor neurons

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

Gamma motor neurons: intrafusal muscle fibers. REGULATE movement

How well did you know this?

Not at all

Perfectly

what do LMN lesions cause

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

How well did you know this?

Not at all

Perfectly

what do UMN lesions cause

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

How well did you know this?

Not at all

Perfectly

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

LMN: decreased
UMN: increased

How well did you know this?

Not at all

Perfectly

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

LMN: decreased
UMN: increased

How well did you know this?

Not at all

Perfectly

is strength increased or decreased with LMN lesion? UMN?

decreased for both

How well did you know this?

Not at all

Perfectly

motor unit

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

How well did you know this?

Not at all

Perfectly

largest myofiber unit

antigravity muscle up to 1000 myofibers/unit

How well did you know this?

Not at all

Perfectly

where are motor neurons located in the spinal cord

anterior horn (ventral)

How well did you know this?

Not at all

Perfectly

Neurons controlling axial muscles are ____ to those controlling distal muscles

medial

How well did you know this?

Not at all

Perfectly

Neurons controlling flexors are located ____ to the extensor groups

posterior

How well did you know this?

Not at all

Perfectly

type I dark muscle fibers
Action
Lipids
Glycogen
Ultrastructure
Physiology
Protoype

action: sustained force weight bearing. long contractions
Lipids: abundant
glycogen: scant
ultrastructure: many mitochondria
Physiology: slow twitch
Prototype: turkey leg

How well did you know this?

Not at all

Perfectly

Type II white muscle fibers Action
Lipids
Glycogen
Ultrastructure
Physiology
Protoype

A: sudden movements, purposeful motion. short
L: Scant
G: Abundant
U: few mitochondria
P: Fast twitch
Pro: turkey breast

How well did you know this?

Not at all

Perfectly

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

just one; no mixing

How well did you know this?

Not at all

Perfectly

does it take more motor units to jump or stand?

jump

How well did you know this?

Not at all

Perfectly

why is the cortex hierarchical

because it decides what movements should occur

How well did you know this?

Not at all

Perfectly

functions of premotor cortex

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

How well did you know this?

Not at all

Perfectly

motor control is in ____ arrangment

parallel

How well did you know this?

Not at all

Perfectly

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

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

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

basal ganglia, cerebellum, and association cortex

damage to the BG, cerebellum and association cortex causes

involuntary movement, gncoordingation, difficulty initiating movement but NOT weakness

descending motor pathways mostly terminate or synapse on

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

what are the descending motor pathways

corticospinal tract, corticobulbar tract, ccorticopontine tract

another name for corticospinal tract

pyramidal tract. cortex to spine

the primary motor cortex is referred to as area?

area 4 (40% fibers)

function of primary motor cortex

execution of CONTRALATERAL voluntary movements and control of FINE DIGITAL movements

the spinal cord motor neurons to the hand have ____ terminations

monosynaptic

lesions to the primary motor cortex can lead to paralysis of

ctonralateral muscles

premotor cortex is referred to as area?

area 6. on lateral aspect of cerebrum

premotor cortex fibers project to

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

lesions in the premotor cortex cause?

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

function of supplementary motor cortex

plans movements while thinking. 1. assembles new sequence (playing new music) 2. assembles previously learned sequence (music scale) 3. imagines movmeents

the supplementary motor cortex project into the

premotor and primary motor cortex areas

what modulates sensory signals

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

why is the corticospinal tract a complex tract

it has multiple origins and destinations

collaterals of the corticospinal tract project to

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

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

fine finger movement because it synapses directly onto the LMN

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

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

what is it called when coritcopsinal tract fibers cross the midline

pyramidal decussation

the corticospinal tract originates in the

cerebral cortex, pre central gyrus and nearby areas

what three areas does the corticospinal tract descend thru before decussation

cerebral peduncle, basis pontis, and medullary pyramid

where does the coricospical tract (CST) decussate

spinomedullary junction

where does the corticospinal tract synapse

on either cell bodies in the anterior horn or interneurons

amount of uncrossed and crossed fibers in the CST

lateral- 80% cross in medulla and descend in LATERAL FUNICULUS uncrossed- 10% Anterior- 10% uncrossed and descend in the ANTERIOR FUNICULUS

function of the Vestibulospinal tract

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

function of the rubrospinal tract

control of shoulder and proximal arm musculature

function of the reticulospinal tract

control axial musculature- walking rhythmic motion

function of the tectospinal tract

head turning reflexes in response to visual stimuli

origin of vestibular spinal tract

vestibular nuclei in ons

where do the vestibulospinal tracts receive input from

vestibular system and cerebellum

facilitates antigravity muscles

vestibulospinal tract

origin of rubrospinal tract

red nucleus

what are the two reticultospinal tracts

Medial: pons; ipsilateral descends near MLF in anterior funicular lateral: medulla, descends bilaterally in lateral funiculus