Nerve Anatomy Flashcards

1
Q

Innervation ratio

A

number of muscle fibers one axon innervates.

Muscle fibers : 1 axon

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2
Q

innervation ratio of gross vs fine movement

A

gross movement has a high IR (lots of muscles innervated by one axon).
Fine movement has a low IR (less muscles innervated by one axon).

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3
Q

innervation ratio and force generation

A

the higher the IR, the greater the force generated by the motor unit

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4
Q

myotome

A

group of muscles innervated by 1 spinal segment

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5
Q

what motor neuron innervates extrafusal fibers

A

alpha-motor neurons

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6
Q

what motor neuron innervates intrafusal fibers

A

gamma-motor neurons

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7
Q

2 types of intrafusal fibers

A

Nuclear bag and nuclear chain

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8
Q

3 layers of nerve connective tissue, from out to in

A
  1. Epineurium
  2. Perineurium
  3. Endoneurium
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9
Q

renshaw cell

A

inhibitory interneuron

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10
Q

three types of motor neurons

A
  1. alpha
  2. beta
  3. gamma
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11
Q

what type of motor neuron does needle EMG evaluate?

A

alpha motor neurons

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12
Q

what fibers does each type of motor neuron innervate

A
  1. alpha = extrafusal
  2. beta = extrafusal and intrafusal
  3. gamma = intrafusal
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13
Q

what does the henneman size principle say?

A

small alpha motor neurons are recruited first during voluntary contraction and large alpha motor neurons are recruited later when more motor units are needed to generate contraction.

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14
Q

correlation between size of alpha motor neuron and threshold of excitation

A

small alpha motor neurons have a low threshold.

large alpha motor neurons have a high threshold.

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15
Q

3 different types of muscle fibers

A

Type 1
Type 2a
Type 2b

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16
Q

Type 1 muscle fiber:

  1. Contraction time
  2. Diameter
  3. Resistance to fatigue
  4. Force
  5. Innervation Ratio
A
  1. Slow
  2. Small
  3. High/Aerobic
  4. Small
  5. Low (fine movements)
17
Q

Type 2a muscle fiber:

  1. Contraction time
  2. Diameter
  3. Resistance to fatigue
  4. Force
  5. Innervation Ratio
A
  1. Fast
  2. Medium
  3. Moderate/Long-term anaerobic
  4. Moderate
  5. High (gross movement)
18
Q

Type 2b muscle fiber:

  1. Contraction time
  2. Diameter
  3. Resistance to fatigue
  4. Force
  5. Innervation Ratio
A

1 . Very Fast

  1. Large
  2. Small/short-term anaerobic
  3. Very High
  4. High (gross movement)