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Neuroanatomy > Muscle Spindle, GTO, Muscle fibres > Flashcards

Muscle Spindle, GTO, Muscle fibres Flashcards

1
Q

Name the 2 types of muscle fibres

A

Slow twitch/ Type I

Fast twitch/ type II

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2
Q

How do slow twitch fibres obtain their energy

A

Oxidative metabolism (hence rich in enzymes)

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3
Q

How do fast twitch fibres obtain their energy

A

Faster glycolytic process

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4
Q

Which type of fibres are ore resistant to fatigue

A

Slow twitch are have increased resistance to fatigue

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5
Q

What type of activities are slow twitch fibres well suited for

A

Activities related to physical effort requiring strength and endurance that depend for energy metabolism on oxidative processes

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6
Q

What type of activities are fast twitch fibres well suited for

A

Suited to rapid alternating effort

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7
Q

Why is there a difference in the types of activities each fibre is suited for

A

Glycogen stores are more rapidly depleted than oxygen supplies, hence why type 2/fast twitch fibres are less suited for continuous types of activity

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8
Q

Which fibres are more prone to anatomic changes to altered energy demands

A

Type II/fast twitch are more prone, as they can increase in number in adults that increase their strenous exercise

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9
Q

What does a motor unit consist of

A

single alpha motor neuron and the muscle fibres it innervates–> this includes motor end plate

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10
Q

How many muscle fibres are there are fine movements compared to larger musculature

A

Muscles for fine movement will have only a few muscle fibres

In large musculature, a single motor unit may innervate many hundreds of muscle fibres

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11
Q

What is the neuromuscular junction

A

Where an alpha motor neuron enters the skeletal muscle and branches, terminating at the motor end plate (where muscle fibre synapses with skeletal muscle)

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12
Q

Give an example of and explain a pathology that targets the NMJ

A

Myasthenia Gravis:
Muscle weakness
Autoimmune disease
Antibodies against acetylcholine receptor hence the neurotransmitter is not able to be received by post synaptic neuron

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13
Q

Example muscle tone during resting periods

A

Muscle is always in a partial state of contraction
There is no intermediate stage (all or none response) hence a few muscle fibres within the muscle must be contracted at all times to maintain tone

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14
Q

How do muscle fibres maintain tone without getting fatigued

A

Asynchronous firing
Different groups of motor units are bought into action at different times through asynchronous firing of nervous impulses in the motor neurons in VH (alpha motor neuron)

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15
Q

Name some poprioceptive receptors/mechanisms

A

Muscle spindle–> detect change in length
GTO–> detect change in muscle tension
Inner ear–> gives information about position of head and hence balance
Eye are also proprioceptive

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16
Q

What makes up a muscle spindle?

A

Intrafusal muscle fibres–> nuclear chain and bag fibres

17
Q

Where are muscle spindles found

A 
In skeletal (striated) muscle, and lie in the long axis of extrafusal muscle
They lie in the same plane and direction as the muscle action in order to detect the change in length
18
Q

Where are muscle spindles most numerous

A

at tendinous attachment of muscle, here can detect change in length best
Especially numerous in muscles that perform highly skilled movement (e.g. hand)

19
Q

What nerve is extrafusal muscle mass innervated by

A

Alpha motor neuron

20
Q

What nerve innervates intrafusal muscle fibres

A

Gamma motor neuron

21
Q

What is the role of the nerve that innervates intrafusal muscle fibres

A

Gamma motor neuron keeps intrafusal fibres tuat so that they are able to pick up changes in length and the rate of change

22
Q

What are nuclear bag fibres

A

Numerous nuclei present in the centre
Expanded fibres (larger in diameter- ‘belly’)
Extend beyond CT capsule at each end to attach to extrafusal fibres

23
Q

What are nuclear chain fibres

A

Nuclei ‘line up’ to form a ‘chain-like’ structure
Small in diameter and more narrow fibre (tube like shape)
Do not extend beyond the CT capsule

24
Q

How many intrafusal muscle fibres are there within each spindle

A

2-14 intrafusal muscle fibres per spindle
Must have an even number of intrafusal muscle fibres because you have a nuclear bag and chain fibre to each muscle spindle

25
Q

Name the 2 types on sensory innervation in muscle spindle

A 
Annuospiral ending (Type Ia afferent)
Flower-spray endings (Type II afferent)
26
Q

What are annulospiral endings

A 
Type Ia afferent 
Primary nerve endings
Closer to the centre of the spindle
Detect both change in length and rate of change
More highly myelinated, hence faster
27
Q

What are flower spray endings

A

Type II afferent
Secondary nerve endings
Closer to the ends of the spindle
Only detect change in length

28
Q

Function of GTO

A

Detect changes in muscle tension (typically when muscle is concentrically/eccentrically contracted)

29
Q

Where are golgi tendon organs located

A

Present in tendons, located near musculotendinous junciton

30
Q

How is a GTO formed

A

Consists of a fibrous capsule surrounding a small bundle of loosely arranged collagenous fibres
Composed of skeletal muscle cells (extrafusal muscle fibres) which enter a funner-like capsule that is filled with collagen fibre bundles
Nerve fibres are entwined throughout these collagen fibres and are triggered when tension in the muscle is transferred to the collagen fires of the GTO

31
Q

How do GTO respond to increased muscle tension/contraction exerted on a tendon

A

By inhibiting further muscle tension

32
Q

What is the effect of GTO on agonnist and antaogonist

A

GTO action is inhibitory on agonist and excites the antagonist
this decreases tension and hence is protective (prevents muscle tears)

33
Q

How do muscle spindles and GTO respond to isoetric contraction

A

Muscle spindle–> decrease in firing rate of nerve impulse as there is no change in length in muscle spindle
GTO–> increase in firing rate of nerve impulses as there is an increase in tension

34
Q

How to muscle spindle and GTO respond to passive stretching

A

Muscle spindle and GTO both discharge/increase firing rate, however firing rate of GTO is much less than muscle spindle as there is not as much increase in tension as there is in length

35
Q

How do muscle spindle and GTO respond to active contraction

A

Muscle spindle increases nerve impulses during the initial stage of contraction, however as contraction continues it decreases as the change in length inst as significant
GTO firing increases as build up/increase in tension

Neuroanatomy (18 decks)

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