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3rd Year - Neurology > Peter's Physiology 5 - Motor units, muscle spindles, golgi tendon organs and joint receptors > Flashcards

Peter's Physiology 5 - Motor units, muscle spindles, golgi tendon organs and joint receptors Flashcards

1
Q

In general, what do LMNs receive input from? (3)

A

UMN’s
Proprioceptors
Interneurons

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2
Q

What type of motor neurones innervate the bulk of fibres within a muscle that generate force?

A

Alpha motor neurones

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3
Q

What type of motor neurones innervate the muscle spindle?

A

Gamma motor neurones

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4
Q

What is the word used when 2 muscles work together to produce the same movement?

A

Synergistic muscles

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5
Q

What is the name for 2 muscles which oppose each other?

A

Antagonistic muscles

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6
Q

What type of muscles are biceps brachii and brachialis muscles?

A

Synergistic muscles

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7
Q

What type of muscles are biceps brachii and triceps brachii?

A

Antagonists

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8
Q

What is the role of axial muscles?

A

Maintaining posture

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9
Q

Where are proximal (or girdle) muscles found?

A

Shoulder
Elbow
Pelvis
Knee

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10
Q

What do distal muscles move?

A

Hands, feet and digits

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11
Q

How do axons of LMNs exit the spinal cord?

A

In the ventral roots (or via cranial nerves)

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12
Q

Are motor neurones distributed equally within the spinal cord?

A

No - greater number in cervical enlargement and lumbar enlargement

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13
Q

Which spinal cord levels does the cervical enlargement consist of?

A

C3 - T1

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14
Q

Which spinal cord levels does the lumbar enlargement consist of?

A

L1-S3

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15
Q

What’s the name for an alpha-MN and all the skeletal muscle fibres that it innervates?

A

Motor unit

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16
Q

what is the name for the collection of alpha-MN that innervate a single muscle/

A

Motor neurone pool

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17
Q

How do alpha-MNs grade the force of muscle contraction?

A

By changing the frequency of AP discharge of the alpha-MN

By the recruitment of additional, synergistic, motor units

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18
Q

In the anterior horn, how are LMN cell bodies innervating axial muscles situated in comparison to those innervating distal muscles?

A

Axial muscle cell bodies located medial

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19
Q

In the anterior horn, how are LMN cell bodies innervating flexors situated in comparison to extensors?

A

LMNs innervating flexors = dorsal to those supplying extensors

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20
Q

What connects the muscle spindles to an alpha-MN>

A

Central terminal of dorsal root ganglion cells

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21
Q

What does the force produced by innervated muscle fibres depend upon?

A 
Fibre size (hypertrophy)
Fibre phenotype ("fast" or "slow" contracting muscle)
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22
Q

What does summation of alpha-MN twitches cause?

A

A sustaine contraction as the number of incoming action potentials increases

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23
Q

What size of alpha-MN innervate small motor units?

A

Small (soma diameter)

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24
Q

What is another name for the neuromuscular junction?

A

Endplate

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25
Q

What are the 2 major types of skeletal muscle fibres?

A

Slow-oxidative (type I) fibres

Fast (type II) fibres

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26
Q

what are the2 types of fast (type 2) skeletal muscle fibres?

A

Type IIa

Type IIb/ x

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27
Q

What enzyme splits ATP in skeletal muscle fibres?

A

Mysoin ATPase

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28
Q

How is ATP derived in Type I skeletal fibres?

A

Oxidative phsophorylation

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29
Q

Describe speed of contraction and relaxation nd fatigue resistance in type I skeletal muscle fibres?

A

Slow

Fatigue resistant

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30
Q

What colour are type I skeletal muscle fibres?

Why

A

Red fibres

High level of myoglobin

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31
Q

How do type IIa skeletal muscle fibres derive ATP?

A

Oxidative phsophorylation

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32
Q

Describe speed of contraction and relaxation nd fatigue resistance in type IIa skeletal muscle fibres?

A

Fast contract and relaxation

Fatigue resistant

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33
Q

Describe appearance of type IIa skeletal muscle fibres?

A

Red and reasonably well vascularised

34
Q

Describe appearance of type IIb skeletal muscle fibres?

A

Pale and poorly vascularised - white meat

35
Q

How do type IIb/ x skeletal muscle fibres get energy?

A

From glycolysis

36
Q

Describe speed of contraction and relaxation nd fatigue resistance in type IIb skeletal muscle fibres?

A

Fast contraction

Not fatigue resistant

37
Q

Tension of type IIb skeletal muscle fibres?

A

Very high tension

38
Q

Tension of type IIa skeletal muscle fibres?

A

High tension

39
Q

Tension of type I skeletal muscle fibres?

A

Low tension

40
Q

Describe size and threshold of alpha-MN for type IIb skeletal muscle fibres?

A

Large

High threshold

41
Q

Describe size and threshold of alpha-MN for type IIa skeletal muscle fibres?

A

Intermediate

Intermediate threshold

42
Q

Describe size and threshold of alpha-MN for type I skeletal muscle fibres?

A

Small

Low threshold

43
Q

What is the susceptibility of an alpha-MN to discharge action potentials a function of?

44
Q

What allows the fine and graded development of muscle force?

A

Recruitment of alpha motor neurones by size

45
Q

What happens when a skeletal muscle is pulled?

What is this reflex called?

A

It pulls back

Myotatic reflex

46
Q

What sense does muscle spindle contribute to?

A

Non-conscious proprioception

47
Q

What 4 things does a muscle spindle consist of?

A

Fibrous capsule
Intrafusal muscle fibres
Sensory afferents (innervate intrafusal fibres)
Gamma motor neurone (efferents that innervate the intrafusal fibres)

48
Q

What type of reflex arc is a mitotic reflex?

A

Monosynaptic reflex arc

49
Q

Which spinal level is assessed with the supinator deep tendon reflex?

50
Q

Which spinal level is assessed with the biceps deep tendon reflex?

51
Q

Which spinal level is assessed with the triceps deep tendon reflex?

52
Q

Which spinal level is assessed with the quadriceps deep tendon reflex?

53
Q

Which spinal level is assessed with the gastrocnemius deep tendon reflex?

54
Q

What type of neurones supply the non-contractile parts of intrafusal fibres?

A

Ia sensory neurones

55
Q

What type of neurones supply the contractile parts of intrafusal fibres?

A

Gamma motor enurones

56
Q

What happens to the spindle when the gamma MN’s are stimulated?

57
Q

In voluntary movements, describe what happens to gamma-msn?

A

Normally co-activated with alpha-MN so that the intrafusal muscle fibres contract in parallel with the extrafusal fibres = serves function of maintaining the sensitivity of the spindle to stop it getting slack

58
Q

What 2 types of fibres do the intrafusal fibres of muscle spindle contain?

A

Nuclear bag fibres

Chain fibres

59
Q

What are the 2 types of nuclear bag fibres present in muscle spindle?

A

Bag 1/ dynamic

Bag 2/ static

60
Q

What are dynamic (bag 1) nuclear bag fibres sensitive to?

A

Rate of change of muscle length

61
Q

What are static (bag 2) nuclear bag fibres sensitive to?

A

Absolute length of the muscle

62
Q

What are chain fibres in the muscle spindle sensitive to?

A

Absolute length

63
Q

What type of fibres innervate chain fibres of the intrafusal fibres of muscle spindle?

A

Static gamma-MNs

64
Q

What are the 2 types of afferent fibres which innervate intrafusal fibres?

A

Ia afferents

II fibres

65
Q

How do Ia afferents attach to intrafusal fibres?

A

Form a primary annulospiral nerve ending winding around the centre of all intrafusal fibres

66
Q

How do II afferents attach to intrafusal fibres?

A

Form flowerspray endings on all intrafusal fibres except the bag 1 dynamic type

67
Q

What change in intrafusal fibres are Ia fibres more sensitive to?

A

Rate of change

68
Q

What change in intrafusal fibres are II fibres more sensitive to?

A

Absolute length

69
Q

What does stimulation of static gamma fibre cause to happen to steady state, or static response?

A

Causes it to cinrease

70
Q

What does stimulation of dynamic gamma fibre cause to happen to dynamic response to stretch?

A

Enhances it

71
Q

Which type of gamma-MNs in muscle spindle are active when muscle length is changing slowly and predictably?

A

Static gamma-MNs only

72
Q

Which type of gamma-MNs in muscle spindle are active during behaviours which muscle length changes rapidly ad unpredictably?

A

Static and dynamic gamma-MNs

73
Q

Where are golgi tendon organs located?

A

At the junction between the muscle and tendon

74
Q

What is the purpose of golgi tendon organs?

A

Monitor changes in muscle tension

75
Q

How are golgi tendon organs organised in relation to extrafusal fibres?

A

In series with extrafusal fibres

76
Q

What type of sensory afferents innervate golgi tendon organs?

A

Group Ib sensory afferents

77
Q

What is the purpose of golgi tendon organs?

A

Act to protect muscle from overload and more generally regulate muscle tension to an optimal range

78
Q

What reflex are group Ib afferents from golgi tendon organs involved in?

A

Reverse myotatic reflex

79
Q

In what parts of joints are proprioceptive axons located?

A

In connective tissue of joints

80
Q

What is the function of free nerve endings found in capsule and connective tissue?

A

Nociceptive function

81
Q

What is the function of paciniform endings found in periosteum near the articular attachments and the fibrous part of the joint capsule?

A

Acceleration detectors

82
Q

What is the function of Ruffini endings found mainly in joints capsule?

A

Static position and speed of movements

3rd Year - Neurology (17 decks)

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