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3 Neurology > Physiology 5: Motor Units, Golgi Tendon Organs and Joint Receptors > Flashcards

Physiology 5: Motor Units, Golgi Tendon Organs and Joint Receptors Flashcards

1
Q

where are LMNs located?

A

soma within the brainstem

ventral horn of the spinal cord

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2
Q

where are UMNs are located?

A

brain

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3
Q

where do LMNs get input from?

A

UMNs
proprioceptors
interneurons

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4
Q

alpha motor neurons supply what? what does this allow it to do?

A

skeletal muscle for FORCE

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5
Q

gamma motor neurons innervate…

A

muscle spindles

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6
Q

give an example of synergistic muscles

A

brachialis and biceps brachii

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7
Q

axial muscles control movements of…

A

the trunk for posture

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8
Q

axons of LMNs exit the spinal cord via..

A

anterior/ventral roots OR

cranial nerves

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9
Q

where is the greatest number of motor neurons?

A 
cervical enlargement (C3-T1)
lumbar enlargement (L1-S3)
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10
Q

name the roots of the cervical enlargement and what they supply

A

C3-T1

arm

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11
Q

name the roots of the lumbar enlargement and what they supply

A

L1-S3

leg

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12
Q

a motor unit it is made up of?

A

an alpha motor neurone and all of the skeletal muscle fibres it innervates

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13
Q

what is a motor neurone pool?

A

a collection of alpha motor neurones that innervate a single skeletal muscle

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14
Q

LMNs supplying what structures exist most medially in the anterior horn of the spinal cord

A

axial structures (distal muscle LMNs are more lateral)

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15
Q

LMNs supplying flexors are __ to those supplying extensors

A

dorsal

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16
Q

muscle strength depends on what 2 things?

A

neuromuscular activation eg firing and number of LMNs AND

force production by innervated muscle fibres eg fibre size and phenotype

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17
Q

a single AP in an alpha MN causes what to happen to a muscle fibre?

A

it will twitch

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18
Q

multiple APs in an alpha MN cause what to happen to a muscle fibre?

A

will contract

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19
Q

slow motor units are recruited before large motor units T or F

A

T

20
Q

the speed of a skeletal muscle fibre depends on…

A

how fast myosin ATPase splits ATP to provide energy for cross bridge cycling

21
Q

dark red fibres are an example of fast or slow mucle fibres?

A

slow as they contain alot of myogloin

22
Q

which type of skeletal muscle fibres are fatigue resistant and contract fast?

A

type 2a

23
Q

which type of skeletal muscle fibres are not fatigue resistant and are poorly vascularised? how fast do they contract?

A

type 2b

fast

24
Q

which type of skeletal muscle fibres fatigue the quickest?

A

type 2b

25
Q

a high tension muscle with a low fatigue threshold will have how many alpha MNs

A

a lot

26
Q

what is the myotatic reflex?

A

the pulling back of a skeletal muscle

27
Q

what do muscle spindles sense?

A

changes in length to the muscle

28
Q

what kind of motor neurone afferents do spindle fibres have?

A

gamma MN

29
Q

excitatory synaptic transmission in the spinal cord is mediated by what substance?

A

glutamate

30
Q

what is a monosynaptic reflex?

A

a reflex that only requires afferent/efferent neurons to synapse once

31
Q

the myotatic reflex is an example of a __synaptic reflex

A

mono

32
Q

stimulation of gamma MNs in muscle spindles causes what?

A

contraction of the spindle fibres

33
Q

sensory and motor input of intrafusal fibres in spindle fibres?

A

sensory - sensory afferents (1a to centre, spinal roots to polar ends)
motor - gamma MNs

34
Q

which type of sensory afferent fibres are the fastest conductors?

A

type 1a

35
Q

when would dynamic gamma MNs be needed?

A

when muscle length changes rapidly and unpredictably

36
Q

where are golgi tendon organs lcoated

A

junction of muscle and tendon

37
Q

what do golgi tendon organs do?

A

monitor changes in muscle tension

38
Q

golgi tendon organs are innervated by…

A

group 1b sensory afferents

39
Q

what sensory neurons initiate the reverse myotatic reflex?

A

group 1b sensory afferents

40
Q

how is the myotatic reflex mediated

A

an inhibitory interneuron needs to be between the 1b afferent and an alpha MN

41
Q

where are joint proprioceptors located?

A

joint connective tissue

42
Q

what structures are in charge of sensing pain in the joint?

A

free nerve endings

43
Q

activation of gamma MNs comes from…

A

ventral horn of the spinal cord in response to a signal from the brainstem or cerebrum i.e NOT A REFLEX

44
Q

alpha MN stimulation without gamma MN stimulation would have what effect on the muscle?

A

would be floppy as no stimulation to the muscle spindle (which keeps the muscle tight)

45
Q

what nuclear bag fibres are sensitive to rate of change of muscle length?

A

bag 1 dynamic

46
Q

bag 2 nuclear fibres are sensitive to…

A

absolute length of the muscle

3 Neurology (41 decks)

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