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EXCI 360 > lower motor unit > Flashcards

lower motor unit Flashcards

1
Q

what are the 4 system essential to motor control

A

local spinal cord and brainstem circuits
descending control centers in the cerebral cortex and brainstem
cerebellum
basal ganglia

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2
Q

role of local circuit neuron

A

sensorimotor integration and central generation

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3
Q

role of motor cortex

A

planning, innitiating and directing voluntary mvt

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4
Q

role of brainstem center

A

rhytmic, stereotyped movement and postural control

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5
Q

basal ganglia

A

iniation of intended movement
suppression of unwanted movement

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6
Q

role of cerebellum

A

coordination of ongoing movement

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7
Q

MN innervating how many muscle and regrouped where

A

All MNs innervating a single muscle are grouped together into a rod-shaped cluster in the ipsilateral ventral horn that runs parallel to the long axis of the spinal cord for one or more spinal cord segments.

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8
Q

MN innervating how many muscle and regrouped where

A

All MNs innervating a single muscle are grouped together into a rod-shaped cluster in the ipsilateral ventral horn that runs parallel to the long axis of the spinal cord for one or more spinal cord segments.

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9
Q

Mn innervating the axial musculature (postural muscle of trunk) are located where

A

most medially in the ventral horn of the spinal cord.

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10
Q

MN that innervate the muscles of the shoulders (or pelvis ) are located where

A

lateral to the axial neuron

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11
Q

MN that innervate proximal muscle of the arm or leg are located where

A

next one most lateral in ventral horn of sc

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12
Q

MN that innervate the distal part of extremities (hand, finger, toes, feet) are located where

A

lies farthest from the midline of ventral horn of SC

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13
Q

Pathways that contact the medial parts of the spinal cord gray matter are involved primarily in

A

control of posture and locomotion

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14
Q

Local circuit neurons that supply the medial region of the ventral horn are located

A

medially within the intermediate zone of the spinal cord gray matter

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15
Q

Local circuit neurons that supply the medial region of the ventral horn have axons extending over where

A

over several spinal cord segments and terminate bilaterally

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16
Q

Pathways that contact the lateral parts of spinal cord grey matter are involved in

A

fine control of the distal extremities

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17
Q

Local circuit neurons that supply the lateral parts of the ventral horn:
located

A

more laterally

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18
Q

Local circuit neurons that supply the lateral parts of the ventral horn have axons extending over

A

just a few spinal cord segments and terminate on the same side of the cord as the cell body

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19
Q

the two types of lower MN are found where

A

MN pools of ventral horn

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20
Q

large alpha MN innervate what

A

skeletal muscle extrafusal fibers that generate the forces needed for posture and movement.

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21
Q

smal y MN innervate what

A

specialized intrafusal muscle fibers (muscle spindles) that are sensory receptors arranged in parallel with the force-generating extrafusal muscle fibers.

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22
Q

muscle spindle are innervated by and role

A

small y sensory axons that transmit information about the length and change in length of the muscle.

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23
Q

role of y MN

A

to regulate this sensory input by setting the intrafusal muscle fibers to an appropriate length.

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24
Q

skeletal muscle fiber are innervated by how many alpha MN

A

only one

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25
Q

each alpha MN synapse with how many fiber in muscle

A

multiple

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26
Q

what define the motor unit

A

The alpha motor neuron and the muscle fibers it contacts

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27
Q

muscle fiber from same motor unit are distributed over what

A

wide area within muscle

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28
Q

what consitutute the smallest unit of force that can be activated in the muscle

A

motor unit

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29
Q

does motor unit is the only one varying in size

A

no also alpha MN

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30
Q

small alpha MN innervate which type of motor unit

A

relatively few muscle fibers and form motor units that generate small forces.

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31
Q

large alpha Mn innervate which type of motor unit

A

larger and more powerful motor unit

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32
Q

motor unit differ in what

A

type of muscle fiber that they innervates and size

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33
Q

what are the 3 type of motor unit in relation of which muscle fiber they innervate

A

slow motor unit
fast fatiguable motor unit
fast fatigue-resistant motor unit

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34
Q

which type of motor unit comprise small “red” muscle fibers that contract slowly and generate relatively small forces.

A

slow motor unit, smaller Mu

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35
Q

which type of muscle unit are resistant to fatigue

A

slow motor unit and fast-fatigue resistant

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36
Q

which type of motor unit containt rich myoglobin content, plentiful mitochondria, and rich capillary beds

A

slow motor unit

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37
Q

slow motor unit are require for what

A

For activities that require sustained muscular contraction, such as maintaining an upright posture.

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38
Q

which type of motor unit is Larger MUs innervate larger, pale muscle fibers that generate fast, large forces.

A

fast fatiguable

39
Q

which type of motor unit is easily fatiguable and why

A

fast fatiguable bc of sparse mitochondria

40
Q

when we run or jog which motor unit are required

A

fast fatigable

41
Q

fast fatigable motor unit are required when

A

For brief exertions that require large forces, such as running or jumping.

42
Q

which type of motor unit are Intermediate size MUs generate about twice the force of a slow MU

A

fast fatigue-resistant motor unit

43
Q

which motor unit generate the higher force during change in muscle tension in response to a single AP

A

fast fatiguable, peak fast and return to normal fast

44
Q

which type of motor unit generate the lowest force in responses to change in muscle tension in response to a single AP

A

slow motor unit

45
Q

what happen if you repeated stimulation in slow motor unit

A

keep generate same amount of force

46
Q

what happen if you repeated stimulation in fast fatiguable

A

peak and after a time there no more force while small have still constant force generating

47
Q

MU are recruited how

A

according to there size -> small one first and bigger one after

48
Q

what happen as the activity of axon that provide input to the pool of lower MN increase

A

low threshold slow motor unit are recruited first -> 5% force
then fast fatigable resistance motor unit are recruited -> 20% force
Than at the highest level of activity, fast fatigable motor unit are recruit -> 75%

49
Q

when you standing for a long period of time which type of motor neuron (unit) are recruits

A

slow

50
Q

when you walk or run which motor unit are recruited

A

fast-fatigue resistant

51
Q

when you gallop or jumping which motor unit are recruited

A

fast-fatiguable

52
Q

the frequency of AP generated by MN contribute to what and what also contribute to that

A

regulation of muscle tension -> muscle spindle

53
Q

what happen when the muscle fibers are activated by the next action potential before they have time to completely relax,

A

force generated are summed so increase

54
Q

which motor unit are recruits first

A

small one and the one generated the least amount of voluntary force (lowest threshold)

55
Q

As the individual generates more and more force what happen

A

number and rate of firing of active motor unit increase

56
Q

what happen with alpha motor neuron, when motor unit increased in size

A

alpha MN have increased: cell body, dendritic complexity, short-term EPSP, axonal diameter (faster conduction) and increase in number of axonal branches (more muscle fiber innervated)

Alpha MN have decreased in input resistance, excitability, Ia EPSP amplitude, PSP decay constant, durant of after-hyperpolarization

57
Q

what is varying with spectrum of fiber phenotypes possess in skeletal muscle

A

in speed of contraction, tension, generation oxidative capacity, and endurance.

58
Q

caractéristic of alpha MN that serve small motor unit and what is the type of MN in question

A

easily depolarized to firing threshold and typically maintain only slow, steady rates of firing
slow muscle fiber

59
Q

characteristic of alpha MN that serve large motor unit

A

are more difficult to depolarize to threshold but are capable of achieving high frequencies of firing.
type FF muscle fibers

60
Q

characteristic of alpha MN that serve large motor unit

A

are more difficult to depolarize to threshold but are capable of achieving high frequencies of firing.
type FF muscle fibers

61
Q

how can physiological proprieties of slow and fast fiber can be reversed

A

surgically altering the innervation to these fibers (innervating type S muscle fibers with a nerve that typically supplies FF muscle fibers, and vice versa).

62
Q

what can the actual pattern of neural activity in a motor nerve can prod=vide

A

instructive signal that can influence the expression of muscle fiber phenotype.

63
Q

chronic electrical nerve stimulation can transform which type of motor unit in which other type

A

FF to slow fiber

64
Q

alpha MN can be modified toward which type of motor unit

A

slow, fatigue-resistant motor unit

65
Q

exercise regime can do what to the contractile propriety of motor unit

A

slow the contractile and increasing the endurance and strength of muscle fibers

66
Q

slow motor unit are affected at which level of exercise level

A

low exertion

67
Q

FR and FF motor unit are affected by which type of exercise

A

higher intensity of exercise

68
Q

what is the other reason that a motor fiber can generate more force following training

A

exercise had increase the rate of muscle unit firing

69
Q

what are the 2 classes of intrafusual fiber

A

nucleus bag fibre (dynamic and static)
nuclear chain fiber

70
Q

what are the 2 classes of intrafusual fiber

A

nucleus bag fibre (dynamic and static)
nuclear chain fiber

71
Q

what are the 2 classes of sensory axons during stretch reflex

A

group Ia, group II

72
Q

groupe Ia respons to what and are around what

A

coiled around middle region, respond to pashically to small stretch

73
Q

group II respons to what and are located where

A

contact just outside the middle region ( nuclear chain fiber and static nuclear bag fiber)
signal the level of sustained fiber stretch

74
Q

sensory signal for the stretch reflex originates where

A

muscle fiber

75
Q

what happen during the stretch reflex circuitry

A

The stretch imposed on a muscle deforms the intrafusal muscle fibers, which in turn initiates APs by activating the mechanotransduction channels in the group I and II axon endings innervating the spindle.

76
Q

what is excited during stretch reflex and what is inhibit

A

excited:monosynaptic excitatory connections with MNs that innervate the same muscle and synergistic muscles.

inibihit: antagonist muscle via !a inhibitory interneuron

77
Q

the arrangement of sensory neuron in stretch reflex result in what

A

rapid contraction of the stretched muscle and simultaneous relaxation of the antagonist muscle.

78
Q

the arrangement of sensory neuron in stretch reflex result in what

A

rapid contraction of the stretched muscle and simultaneous relaxation of the antagonist muscle.

79
Q

what control the functional characteristics of the muscle spindles by modulating their level of excitability during stretch reflex

A

smaller y MN

80
Q

role of smaller Y MN during stretch reflex

A

control the functional characteristics of the muscle spindles by modulating their level of excitability.

81
Q

role of Dynamic y MN during stretch reflex

A

enhance dynamic response of group Ia afferents.

82
Q

role of static y Mn during stretch reflex

A

enxhance static réponse of group II afferent

83
Q

how can the gain of stretch reflex can be change

A

by adjusting the level of excitation of a and g MNs.

84
Q

arrangement of GTO and location

A

located at the junction of the muscle and the tendon. They are arranged in series with extrafusal muscle fibers.

85
Q

what happen when mechxnosensitive ion channel are activated in the nerve ending of GTO

A

organ triggers APs that propagate along the group Ib axon

86
Q

what happen when mechxnosensitive ion channel are activated in the nerve ending of GTO

A

organ triggers APs that propagate along the group Ib axon

87
Q

the arrangement of Ib afferent and inhibitory prevent what (GTO)

A

arrangement prevents muscles from generating excessive tension and helps maintain a steady level of tone during muscle fatigue.

88
Q

Ib inhibitory interneuron of GTO receive input from

A

Ib afferent upper MNs, cutaneous receptors, muscle spindles, and joint receptors

89
Q

what happen in GTO when Ib afferent contact Ib inhibitory interneuron

A

decrease the activity of  motor neurons innervating the same muscle.

90
Q

what happen when Ib afferent contact excitatory interneuron in GTO

A

activate  motor neurons innervating antagonistic muscles.

91
Q

what happen when Ib afferent contact excitatory interneuron in GTO

A

activate  motor neurons innervating antagonistic muscles.

92
Q

what happen when extrafusual muscle fiber contract by stimulation of alpha motor neuron

A

muscle spindle is unloaded and its activity decrease

rate of GTO firing increase

93
Q

explain the flexion-crossed extension reflex

A

Stimulation of nociceptors in the foot leads to activation of spinal cord local circuits that serve to -> excited flexor and inhibited extensor of the foot that receive the stimulus and excited extensor and inhibited flexor of the other foot to provide compensatory support

94
Q

explain the flexion-crossed extension reflex

A

Stimulation of nociceptors in the foot leads to activation of spinal cord local circuits that serve to -> excited flexor and inhibited extensor of the foot that receive the stimulus and excited extensor and inhibited flexor of the other foot to provide compensatory support

EXCI 360 (14 decks)

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