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DPT 503 > Motor Systems > Flashcards

Motor Systems Flashcards

1
Q

what is the descending system?

A

upper motor neurons

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2
Q

what does the descending system consist of?

A

motor cortex, and BS centers

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3
Q

what are the SC and BS circuits?

A

local circuit neurons and motor neuron pools (lower motor neurons)

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4
Q

where does the LMN get commands from?

A

UMNs and local circuitry

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5
Q

what are the LMNs?

A

alpha motor neurons and gamma motor neurons

convey signals to the intrafusal and extrafusal muscle fibers

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6
Q

what are alpha motor neurons?

A

large myelinated

extrafusal (typical muscles fibers that are contractible)

somatotopic organization

bodies in the ventral horn

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7
Q

what is the motor neuron pool?

A

group of alpha motor neurons innervating one muscle

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8
Q

what is the somatotopic organization of the motor pool?

A

medial ventral horn-proximal muscles

lateral ventral horn-distal muscles

ventral ventral horn-extensors

dorsal ventral horn-flexors

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9
Q

what is the spatial distribution of the motor pool?

A

extends several SC segments

longitudinal distribution

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10
Q

what are gamma motor neurons?

A

medium myelinated

intrafusal (in the middle of the muscle spindle)

bodies in the ventral horn

3 parts: muscle spindles, efferent connections, and afferent connection

axons terminate at contractile portion of spindle

all 3 fibers (bag static and dynamic and chain)

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11
Q

what are muscle spindles

A

sensory receptor in muscle

in belly of muscles (thickest part)

group 1a and 2 afferents and gamma motor neuron

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12
Q

what are the roles of muscles spindles?

A

detect absolute muscle length and changes in muscle length

fine regulation of muscles length during movement

active lengthening and shortening and passive lengthening

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13
Q

high spindle density= ___ motor control

A

fine

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14
Q

intrafusal fibers

A

nuclear bag fibers and nuclear chain fibers within the muscle

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15
Q

nuclear bag fibers

A

static: detects changes in muscle length

dynamic: detects rate of change in muscle length

spherical nuclei

elastic

stretches quickly

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16
Q

nuclear chain fibers

A

static: only detects change in muscle length, not rate for change

single row of nuclei

less elastic

stretches slowly

long/sustained stretch

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17
Q

group 1a afferents

A

large diameter

faster

myelinated

wrap around equatorial region of bag and chain fibers (non contractile region)

rate of change (dynamic/phasic)

fire with acute change in muscle length but not when there’s a sustained change

stops firing when there’s no longer an ongoing change

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18
Q

group 2 afferents

A

medium diameter

slower

myelinated

next to equator in polar region (contractile region)

steady state-tonic

static lengthened/shortened=constant firing

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19
Q

which causes more afferent activity: a passive stretch or active shortening?

A

passive stretch causes more afferent activity

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20
Q

what are gamma dynamic fibers?

A

activate only nuclear bag fibers ]

enhance response of group 1a neurons by adjusting sensitivity of dynamic bag

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21
Q

what are gamma static fibers?

A

activate nuclear chain and bag fibers

enhances response of group 1a and 2 neurons

22
Q

what is alpha-gamma co-contraction?

A

intra and extrafusal fibers contracting together

just alpha activated-fiber on slack w/o gamma activation

when both neuron are activated, muscle spindle can operate entirely at an muscle length

23
Q

golgi tendon organ (GTO)

A

sensory receptors

located at MTJ

1b afferent fibers

rod woven into collagen fibers
- contraction-tight-squeezes GTO
- stretch-distortion of GTO

large myelinated axon

no efferent connection

24
Q

what is the role of the GTO?

A

sensitive to tension changes from stretch, contraction, or loading (tonic)

responds to muscles output in response to fatigue
- fatigued muscle=reduced GTO firing, but can still fire some

25
Q

what is the firing pattern of the GTO?

A

muscle passively stretched-less GTO activity

muscle actively contracted-more GTO activity

response of GTO and 1b afferents are more sensitive to active changes in muscle length

26
Q

motor function of the SC

A

integrate somatosensory info

controls of voluntary movement

refine movement plan

27
Q

what is reciprocal inhibition?

A

involves inhibitory interneurons

activation of 1a afferents synapsing onto inhibitory interneurons results in inhibition of the alpha MN innervating the antagonist

when muscle is contracting, antagonist is inhibited

28
Q

what is muscle synergy?

A

group of muscles controlled as a unit

29
Q

what is the body schema?

A

proprioceptive model created by the SC

developed over time

neural rep of body to plan and adapt movement in the SC

nonconscious process

30
Q

GTO during gait

A

stretch of GS tendon activates GTO

stance phase-loaded-GTO activation-autogenic activation of own muscles

unloaded-GTO activated-autogenic inhibition of on muscle

31
Q

locomotor central pattern generator

A

network of spinal interneurons to generate rhythmic, alternating activities of flexion and extension at hips and knees

flexor activated-extensor inhibited

tonic input

ankle needs more proprioceptive input

loaded GTO activated=prolonged stance phase

32
Q

what is autogenic excitation?

A

monosynaptic: only one synapse to cross

faster
less room for other inputs

less modifiability

33
Q

what is reciprocal inhibition

A

disynaptic: has to cross 2 synapses

slower

more room for other circuits to modify the output

34
Q

what is the clinical importance of the stretch reflex?

A

determine integrity of reflex, state of activity of alpha MN pool, and DTR to see if it’s hyperreflexive/hyporeflexive

35
Q

GTO reflexes

A

disynaptic

autogenic inhibition: inhibits own muscle when fully contracted to prevent further contraction
- facilitate antagonist

reciprocal excitation: exciting the antagonist
- protective mechanism

36
Q

what is the withdrawal reflex?

A

touch noxious stimuli, withdrawal limb

excite flexors, inhibit extensors

37
Q

what is the crossed-extension reflex?

A

supporting limb compensates for loss of support when the ipsilateral limb withdraws from a painful stimulus

extensors excited and flexors inhibited on contralateral limb for weight bearing

38
Q

what are the cutaneous reflexes?

A

withdrawal reflex and crossed-extension reflex

39
Q

descending systems

A

reflexive and voluntary movements

40
Q

increased arousal leads to ___ reflex responses

A

heightened

41
Q

relaxation/decreased arousal leads to___ reflex responses

A

decreased

42
Q

what is muscle tone?

A

resistance to muscle stretch

43
Q

what factors contribute to muscles tone?

A

descending motor commands, proprioceptive info, weak cross bridge binding, and titan

44
Q

what is co-contraction?

A

simultaneous contraction of agonist and antagonist muscle to stabilize joints

proximal stabilization

increases stiffness

45
Q

what is the function of the primary motor cortex?

A

voluntary controlled movements

46
Q

what is the function of the premotor area?

A

controls of trunk and girdle muscles, anticipatory postural adjustments

47
Q

what is the function of the supplementary motor area?

A

initiation of movement, orientation planning, bimanual and sequential movements

48
Q

what is the function of Broca’s area?

A

motor programming of speech (usually in L hemisphere)

speech production

49
Q

fine motor function

A

cerebral cortex

lateral corticospinal and rubrospinal tracts

50
Q

postural and gross motor functions

A

BS

medial and lateral vestibulospinal, reticulospinal, and medial corticospinal tracts

51
Q

ambulatory function

A

BS and SC

BS can turn on/off

details by CPG

DPT 503 (22 decks)

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