HES 202- Week 1 Motor Units Flashcards

Week 1- Motor Units

1
Q

What is a motor unit? What is it the functional unit of

A

An alpha motor neuron and all skeletal muscle fibres innervated by its axons. It is the functional unit of contraction

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2
Q

What are the two ways force is controlled by?

A

1) Altering the # of active MU’s (de/recruitment)
2) Changing frequency of activation (rate coding- MU discharge rate)

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3
Q

Describe saltatory conduction?

A

propagation of action potential down the axon

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4
Q

What is myelination?

A

insulates the axon and prevents movement of ions (Na and K) across the membrane

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5
Q

What is the purpose of Nodes of Ranvier

A

Ions move readily at gaps in the myelin sheath (Nodes of Ranvier) so an AP at one node brings the next node to threshold and initiates a new AP

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6
Q

2 benefits to saltatory conduction and myelination

A

1) Increases conduction velocity without a change in axon diameter
2) Reduces metabolic cost as only small segments of the axon require the Na K pump to restore the resting membrane potential

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7
Q

What does Curare prevent binding of? How long does it last for?

A

Prevents binding Ach to Ach receptors. Lasts 8-30 hours.

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8
Q

What does Botox prevent the release of? How long does it last?

A

Ach. Lasts 6-8 weeks.

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9
Q

What are two things Botox is used to treat?

A

Overactive muscles (cerebal palsy) and temporary cosmetic improvements.

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10
Q
A
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11
Q

What are the two MU classifications?

A

Type 1 and Type 2a and Type 2x

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12
Q

What can Type 1 be classified as and what do they innervate?

A

Slow MN that innervate oxidative muscle fibres, forming S MU’s

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13
Q

What can Type 2a be classified as and what do they innervate?

A

Fatigue resistant MN that innervate fast oxidative, glycolytic forming FR MU’s

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14
Q

What can Type 2x be classified as and what do they innervate?

A

Fast fatiguable MN that innervate glycolytic forming FF MUs

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15
Q

What is a twitch?

A

Physiological response of a MU to stimulation

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