JC - Motor Neurones and Reflexes Flashcards

1
Q

What produces a larger voltage nerves or muscles?

A

Muscles produce a larger voltage than nerves as they are greater in size and move more ions

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2
Q

Where do most of the cell bodies reside?

A

Dorsal Root Ganglia

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3
Q

What are some key features of α–Motor Neurones? (4)

A
  • Innervate muscle (no intermediate synapses)
  • Soma is located in ventral horn of spinal cord
  • Occur in “pools” driving different muscles
  • Pools are arranged Topographically
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4
Q

What is unique about α–Motor Neurone innervation?

A

Each muscle fibre/cell is ONLY innervated by ONE α–motor neurone

Each α–motor neurone innervates MANY muscle fibres/cells

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5
Q

Describe the concept of a Motor Unit

A

ONE α–motor neurone PLUS all its muscle fibres

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6
Q

How does stimulation rate affect muscle force?

A

A single motor nerve stimulius produces a twitch (contract and relax)

  • Rapidly repeated stimuli lead to increased force as muscle does not fully relax between stimuli leading to smooth sustained contraction – temporal summation

Muscle force increases with stimulation rate

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7
Q

What are the characteristics of fast-twitch and slow-twitch muscle fibers?

A

Fast-twitch

  • Strong
  • Fatigue quickly
  • Glycolytic

Slow-twitch

  • Weak
  • Fatigue slowly
  • Oxidative
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8
Q

What are the sensors involved in muscle control and what do they consist of?

A

MUSCLE SPINDLES

  • Sit outside muscle fascicle

Consist of intrafusal fibres (within the spindle)

  • Nuclear chain fibres (long)
  • Nuclear bag fibres (swelling)
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9
Q

What do alpha and gamma motor neurones attatch to?

A

Alpha motor neurones attach to muscles outside

Gamma motor neurones attach to muscle spindle

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10
Q

What are Ia afferents, II afferents and Gamma efferents sensitive to?

A

Ia afferents primarily bag fibres:

  • sensitive to rate of change of length (phasic)

II afferents primarily chain fibres:

  • sensitive to length (tonic)

Gamma efferents (motor)

  • control sensitivity via stim of INTRAfusal fibres
    Needed when muscles shorten
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11
Q

What is the Golgi Tendon Organ, and when does it effectively work in muscle control?

A

Golgi Tendon Organ is the ending of a nerve cell wrapped in the collagen of a tendon

  • It works effectively when the muscle is activated, especially when the muscle shortens
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12
Q

Describe the Knee-Jerk Reflex and its feedback loop (5)

A
  1. Applies tension to the muscle
  2. Spindle sends a signal of activation
  3. Doesn’t use brain
  4. Sends signal back to the quadriceps muscle and contracts
  5. Communicates with interneurons, inhibitory response inactivates hamstring muscle
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