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Physiology and Pharmacology > Motor Units And Muscle Spindles > Flashcards

Motor Units And Muscle Spindles Flashcards

1
Q

What is the function of synergistic muscles?

A

They support the main agonist muscles

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2
Q

What are examples of a synergistic relationship?

A

Brachialis and biceps brachii, anconeous and triceps brachii

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3
Q

What is the function of axial muscles?

A

They control the trunk

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4
Q

What is the function of the proximal muscles in shoulder, elbo, plvis and knee?

A

To mediate locomotion

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5
Q

What is the function of distal muscles in the hands, feet and digits?

A

Fine motor movement

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6
Q

What are the two groups of neurons of the somatic NS?

A

Upper and lower

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7
Q

Where do upper neurons arise?

A

In the prmary motor cortex

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8
Q

With what do upper neurons synapse?

A

Lower neurons

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9
Q

What neurotransmitter acts from the upper neuron to stimulate the action potential?

A

Glutamate

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10
Q

Where do lower neurons arise?

A

The spinal cord

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11
Q

From where do the lower neurons recieve the action potential?

A

The upper neurons

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12
Q

Where do the lower neurons synapse?

A

The skeletal muscle target

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13
Q

What are the subtypes of the lower neurons?

A

Alpha neurons innervate bulk fibres in muscle.

Gamma neurons innervate the muscle spindle.

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14
Q

How do lower neurons exit the spinal cord?

A

In spinal nerves

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15
Q

Where are the cell bodies of lower neuron found?

A

In the spnal cord

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16
Q

Where do the lower neurons project?

A

Through the anterior root of the spinal cord

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17
Q

What creates the spinal nerve?

A

Fusion of the posterior and anterior root

18
Q

What is the action of spinal nerves?

A

To end out motor nerves and collect afferent signals

19
Q

How are the spinal nerves named?

A

By the vertebra from which they exit

20
Q

Where do the nerves that create the brachial plexus arise from?

A

C5-T1

21
Q

What is the brachial plexus?

A

The nerves in the neck an shoulders that innervate the arms

22
Q

What area of the body is innervated by nerves from the lumbo-sacral region?

A

The lower limb

23
Q

What will happen following damage to C2?

A

Death as the diaphragm will be paralysed

24
Q

What will be the outcome of injury to T1 nerve?

A

los of function in the lower limb

25
Q

What do maller motor unit allow?

A

Fine motor movement

26
Q

What do larger motor units control?

A

Large muscles like pectorals

27
Q

How do fast and slow muscle fibres differ?

A

In how quickly mysosin ATPase can split ATP for cross bridge cycling

28
Q

What are the characteritics of slow fibres?

A
  • myosin heavy chain
  • High resistance to fatigue
  • rich vaculature system
  • high oxiditave capacity
  • high myoglobin
  • high mitochondria
29
Q

What are the two categories of fast muscle fibres?

A

2A and 2X

30
Q

What are the characteristics of 2A fibres?

A
  • Get ATP from oxidative phosphorylation
  • Fast contraction
  • Fast relaxation
  • Low fatigue resistance
  • Well vascularised
31
Q

What are the characteristics of 2X fibres?

A
  • ATP from glycolysis
  • Fast contraction
  • Less fatigue resistant
  • Poorly vascularised
  • White in colour
32
Q

Are 2A or 2X more common in mammals?

A

2A

33
Q

What does increasing the number of motor neurons do?

A

Increase the force of contraction

34
Q

What causes steady increases in tension?

A

Steady increases of excitabiliy in lower motor neurons

35
Q

What is the order of motor unit recruitment?

A

Slow at low threshold then fast then fast fatigue

36
Q

What is the size principle?

A

The ordered recruitment of motor units

37
Q

What causes a twitch?

A

A single action potential in an alpha neuron

38
Q

What does summtion of twitches lead to?

A

Sustained contraction as the number of action potentials increase

39
Q

When does tension stop appearing as peaks?

A

At 40Hz

40
Q

What re the characterstics of fast fatiguing fibres?

A
  • Very high tension
  • Fast fatiguing
  • Lare a-MN, high threshold
  • Type IIx fibres
41
Q

What are the characteristics of fatigue resistant fibres?

A
  • High tension
  • Slow fatiguing
  • Intermediate a-MN and threshold
  • Type IIa fibres
42
Q

What are the characteristics of slow fibres?

A
  • Low tension
  • Fatigue resistant
  • Small a-MN, low threshold
  • Type I fibres

Physiology and Pharmacology (7 decks)

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