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MED221A/B Lectures > MSK 18 - Motor Control 2 > Flashcards

MSK 18 - Motor Control 2 Flashcards

1
Q

the motor system controls movement together with which other system

A

the sensory system

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2
Q

what are some sensory inputs that assist the motor system

A

retina

vestibular system

auditory system

olfactory system

skin receptors

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3
Q

what are the 4 main receptors controlling movement

A

muscle spindles

golgi tendon organs

pain/nociceptors

joint receptors

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4
Q

what do muscle spindles monitor

A

muscle length

rate of change in muscle length (speed of length change)

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5
Q

what do golgi tendon organs monitor

A

muscle tension when muscles contract

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6
Q

what do joint receptors monitor and what do they signal

A

position

signal hyperextension/hyperflexion at joint

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6
Q

what do pain/nociceptors respond to

A

respond to damaging stimuli or potentially damaging stimuli

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7
Q

what are muscle spindles and where are they located

A

muscle spindles are encapsulated muscle fibres scattered throughout skeletal muscle/extrafusal muscle

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8
Q

muscle spindles are kept in what

A

sheaths

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9
Q

muscle spindles are innervated by what

A

by gamma motor neurons

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10
Q

when gamma motor neurons innervate the spindle fibres is this an afferent/efferent path

A

efferent

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11
Q

when alpha motor neurons innervate the extrafusal muscle is this an afferent/efferent path

A

efferent

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12
Q

what is the difference between extra and intrafusal muscles

A

extrafusal muscle makes up bulk of the muscle

intrafusal muscle are spindle fibres

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13
Q

how are the muscle spindles orientated in relation to the extrafusal fibres

A

lie in parallel

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14
Q

what carries signals from muscle spindle fibres back to CNS

A

group 1a afferent fibres

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15
Q

what is the function of group 1a afferent fibres

A

carries signals from muscle spindle fibres back to CNS

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16
Q

what kind of organs are the golgi tendon organs

A

mechanoreceptive organs

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17
Q

where are the golgi tendon organs located

A

at the myotendinous junction of skeletal muscles

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18
Q

what is the innervation of the golgi tendon organs

A

group 1b afferent fibres

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19
Q

what do group 1b afferent fibres innervate

A

golgi tendon organs

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20
Q

what do golgi tendon organs respond to

A

muscle tension

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21
Q

golgi tendon organs are contained within what structure

A

within a capsule in the tendon

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22
Q

what are reflexes

A

involuntary, stereotypical response of the muscle following stimulation of receptors

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23
Q

reflexes occur following what

A

following successive activation of mutually connected neurons

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24
Q

reflexes occur following successive activation of mutually connected neurons with the last neuron doing what

A

last neuron innervating the effector tissue (muscle)

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25
Q

what makes up a reflex arc

A

neurons and effector tissue (muscle)

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26
Q

what is the basic unit of a reflex

A

reflex arc

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27
Q

reflexes are categorized as what two types

A

monosynaptic and polysynaptic

28
Q

monosynaptic and polysynaptic reflexes are categorised based on what

A

based on how many neurons participate in one reflex arc

29
Q

what are the 4 spinal reflexes

A

stretch/myotatic reflex

reverse/inverse myotatic reflex

flexion reflex

crossed extension reflex

30
Q

in the stretch/myotatic reflex what happens from when a tendon is tapped to the final step of a muscle contraction

A

stretches muscle and sends info back to spinal cord via the 1a afferents from the muscle spindles which can activate motor neurons and get contraction of muscle

31
Q

what does myotatic mean

A

muscle is relaxed

32
Q

what causes muscles to relax in the reverse/inverse myotatic reflex

A

golgi tendon organs - sensors of muscle force in the tendon

33
Q

testing of reflexes allows for what

A

determines the integrity of the motor system and provides information on the condition of the upper and lower motor neurons

34
Q

describe the monosynaptic arc from tendon tap to what structures the signal goes through the brain and back out to the muscle

A

tendon tapped

info goes via sensory receptors to the spinal cord via the dorsal root ganglion then the dorsal root

spinal cord sends back info to the muscles via the ventral root to the peripheral nerve which achieves the motor response in the muscle fibre

35
Q

what are the 5 elements of the stretch reflex in order

describe for a knee jerk reflex

A

receptors - muscle spindles

afferent fibres - type 1a

synaptic central relays - 1a afferents to alpha MN and MN to muscle

efferent fibres - axons of alpha MN

effectors - extrafusal skeletal muscles

36
Q

in the stretch reflex what is the reciprocal

A

reciprocal inhibition

37
Q

why is there reciprocal inhibition involved in the stretch reflex, what nerves are involved in this

A

the 1a afferents to 1a interneurons within the spinal cord inhibits the MNs innervating the antagonist muscles

38
Q

intrafusal muscle fibres have what properties

A

spring like properties

39
Q

what spinal cord segment is responsible for the jaw jerk reflex

A

5th cranial nerve

40
Q

what spinal cord segment is responsible for the bicep jerk reflex

A

C5 and C6

41
Q

what spinal cord segment is responsible for the triceps jerk and finger flexion reflex

A

C7 and C8

42
Q

what spinal cord segment is responsible for the knee jerk reflex

A

L3 and L4

43
Q

what spinal cord segment is responsible for the ankle jerk reflex

A

S1

44
Q

alpha motor neurons innervate which muscle fibres

A

innervates extrafusal muscle fibers

45
Q

are alpha motor neurons afferent/efferent

A

efferent

46
Q

gamma motor neurons innervate which muscle fibres

A

intrafusal muscle fibres

47
Q

are gamma motor neurons afferent/efferent

A

efferent

48
Q

afferent fibres are which fibre types

A

type 1a and type 2 fibres

49
Q

what is the only sensory receptor to have its own motor supply

A

muscle spindle fibers

50
Q

gamma motor neurons innervate what portions of the intrafusal fibres

A

the striated portions of the intrafusal fibres

51
Q

what is the other name for gamma motor neurons

A

fusimotor neurons

52
Q

what is the similarities and difference between type 1a and type 2 endings

A

both are afferents that innervate muscle spindles

differentiated by structure and function

53
Q

what size are the gamma motor neuron cell bodies

A

small

54
Q

do gamma motor neurons have direct input from the proprioceptive sensory afferents, if so where from

A

no

55
Q

what size are the alpha motor neuron cell bodies

A

large

56
Q

do alpha motor neurons have direct input from the proprioceptive sensory afferents, if so where from

A

yes

direct group 1a derived proprioceptive sensory input

57
Q

what do gamma motor neurons monitor and do for muscle fibres

A

keeps muscle spindles at appropriate length so they remain active during muscle shortening

prevents muscle from being overstretched

58
Q

what do alpha motor neurons do for muscle fibres

A

evoke muscle shortening

59
Q

what are the 5 elements of the reverse myotatic reflex in order

A

receptor - golgi tendon organs (in series with the muscle)

afferents - 1b fibres

synaptic relays - 1b afferents to 1b interneurons which inhibit alpha motor neurons

efferents - axons of alpha motor neurons

effectors - muscles

60
Q

what does the reverse myotatic reflex do under extreme circumstances

A

protects muscle from overload in situations that would damage the muscles fibres

61
Q

what does the reverse myotatic reflex do in normal circumstances

A

maintain muscle tension/length in optimal range

62
Q

what is the myotatic reflex

A

when muscle is passively stretched and lengthened

63
Q

what are the neurons involved in the reverse myotatic reflex

A

1b afferents from golgi tendon organ synapse on inhibitory interneurons which inhibits the alpha motor neurons

this decreases contraction of the muscle

64
Q

what are the 5 elements of the flexion/flexor/withdrawal reflex in order

A

receptor - nociceptors

afferents - type 3 and 4 fibres

synaptic relays - to excitatory interneurons which excite flexor alpha motor neurons (afferents project to multiple spinal segments)

efferents - axons of alpha motor neurons

effectors - flexor muscles

65
Q

what does the flexion/flexor/withdrawal reflex do

A

evokes fast withdrawal of limb from a nociceptive stimulus

66
Q

during the withdrawal reflex what do the flexors and extensors do in the affected limb

A

the flexors contract

the extensors relax

67
Q

during the withdrawal reflex what do the flexors and extensors do in the unaffected/other limb

what other reflex is occurring here

A

the flexors relax

the extensors contract

as part of the crossed extensor reflex

68
Q

Why do opposite things happen to the flexor and extensor muscles in the withdrawal reflex

A

maintains balance when nociceptive receptors in the foot are activated

makes sure that the other leg can weight bear when the affected foot is lifted

MED221A/B Lectures (23 decks)

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