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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

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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
What are the 2 major types of skeletal muscle fibres?
Slow-oxidative (type I) fibres | Fast (type II) fibres
26
what are the2 types of fast (type 2) skeletal muscle fibres?
Type IIa | Type IIb/ x
27
What enzyme splits ATP in skeletal muscle fibres?
Mysoin ATPase
28
How is ATP derived in Type I skeletal fibres?
Oxidative phsophorylation
29
Describe speed of contraction and relaxation nd fatigue resistance in type I skeletal muscle fibres?
Slow | Fatigue resistant
30
What colour are type I skeletal muscle fibres? | Why
Red fibres | High level of myoglobin
31
How do type IIa skeletal muscle fibres derive ATP?
Oxidative phsophorylation
32
Describe speed of contraction and relaxation nd fatigue resistance in type IIa skeletal muscle fibres?
Fast contract and relaxation | Fatigue resistant
33
Describe appearance of type IIa skeletal muscle fibres?
Red and reasonably well vascularised
34
Describe appearance of type IIb skeletal muscle fibres?
Pale and poorly vascularised - white meat
35
How do type IIb/ x skeletal muscle fibres get energy?
From glycolysis
36
Describe speed of contraction and relaxation nd fatigue resistance in type IIb skeletal muscle fibres?
Fast contraction | Not fatigue resistant
37
Tension of type IIb skeletal muscle fibres?
Very high tension
38
Tension of type IIa skeletal muscle fibres?
High tension
39
Tension of type I skeletal muscle fibres?
Low tension
40
Describe size and threshold of alpha-MN for type IIb skeletal muscle fibres?
Large | High threshold
41
Describe size and threshold of alpha-MN for type IIa skeletal muscle fibres?
Intermediate | Intermediate threshold
42
Describe size and threshold of alpha-MN for type I skeletal muscle fibres?
Small | Low threshold
43
What is the susceptibility of an alpha-MN to discharge action potentials a function of?
Its size
44
What allows the fine and graded development of muscle force?
Recruitment of alpha motor neurones by size
45
What happens when a skeletal muscle is pulled? | What is this reflex called?
It pulls back | Myotatic reflex
46
What sense does muscle spindle contribute to?
Non-conscious proprioception
47
What 4 things does a muscle spindle consist of?
Fibrous capsule Intrafusal muscle fibres Sensory afferents (innervate intrafusal fibres) Gamma motor neurone (efferents that innervate the intrafusal fibres)
48
What type of reflex arc is a mitotic reflex?
Monosynaptic reflex arc
49
Which spinal level is assessed with the supinator deep tendon reflex?
C5-C6
50
Which spinal level is assessed with the biceps deep tendon reflex?
C5-C6
51
Which spinal level is assessed with the triceps deep tendon reflex?
C7
52
Which spinal level is assessed with the quadriceps deep tendon reflex?
L3-L4
53
Which spinal level is assessed with the gastrocnemius deep tendon reflex?
S1
54
What type of neurones supply the non-contractile parts of intrafusal fibres?
Ia sensory neurones
55
What type of neurones supply the contractile parts of intrafusal fibres?
Gamma motor enurones
56
What happens to the spindle when the gamma MN's are stimulated?
Contracts
57
In voluntary movements, describe what happens to gamma-msn?
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
What 2 types of fibres do the intrafusal fibres of muscle spindle contain?
Nuclear bag fibres | Chain fibres
59
What are the 2 types of nuclear bag fibres present in muscle spindle?
Bag 1/ dynamic | Bag 2/ static
60
What are dynamic (bag 1) nuclear bag fibres sensitive to?
Rate of change of muscle length
61
What are static (bag 2) nuclear bag fibres sensitive to?
Absolute length of the muscle
62
What are chain fibres in the muscle spindle sensitive to?
Absolute length
63
What type of fibres innervate chain fibres of the intrafusal fibres of muscle spindle?
Static gamma-MNs
64
What are the 2 types of afferent fibres which innervate intrafusal fibres?
Ia afferents | II fibres
65
How do Ia afferents attach to intrafusal fibres?
Form a primary annulospiral nerve ending winding around the centre of all intrafusal fibres
66
How do II afferents attach to intrafusal fibres?
Form flowerspray endings on all intrafusal fibres except the bag 1 dynamic type
67
What change in intrafusal fibres are Ia fibres more sensitive to?
Rate of change
68
What change in intrafusal fibres are II fibres more sensitive to?
Absolute length
69
What does stimulation of static gamma fibre cause to happen to steady state, or static response?
Causes it to cinrease
70
What does stimulation of dynamic gamma fibre cause to happen to dynamic response to stretch?
Enhances it
71
Which type of gamma-MNs in muscle spindle are active when muscle length is changing slowly and predictably?
Static gamma-MNs only
72
Which type of gamma-MNs in muscle spindle are active during behaviours which muscle length changes rapidly ad unpredictably?
Static and dynamic gamma-MNs
73
Where are golgi tendon organs located?
At the junction between the muscle and tendon
74
What is the purpose of golgi tendon organs?
Monitor changes in muscle tension
75
How are golgi tendon organs organised in relation to extrafusal fibres?
In series with extrafusal fibres
76
What type of sensory afferents innervate golgi tendon organs?
Group Ib sensory afferents
77
What is the purpose of golgi tendon organs?
Act to protect muscle from overload and more generally regulate muscle tension to an optimal range
78
What reflex are group Ib afferents from golgi tendon organs involved in?
Reverse myotatic reflex
79
In what parts of joints are proprioceptive axons located?
In connective tissue of joints
80
What is the function of free nerve endings found in capsule and connective tissue?
Nociceptive function
81
What is the function of paciniform endings found in periosteum near the articular attachments and the fibrous part of the joint capsule?
Acceleration detectors
82
What is the function of Ruffini endings found mainly in joints capsule?
Static position and speed of movements

3rd Year - Neurology (17 decks)

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