Speed of Conductance Flashcards

1
Q

What three factors affect the speed of conductance/an action potential?

A
  • myelination and saltatory conduction
  • axon diameter
  • temperature
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2
Q

What is an axon?

A

a long, conductive fibre that carries the nervous impulse along the motor neuron

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3
Q

What forms the myelin sheath?

A

Schwann cells

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4
Q

What about the Schwann cells makes them insulators?

A

they are lipids

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5
Q

What is saltatory conduction?

A

the action potential jumping/moving from node to node

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6
Q

why does the myelin sheath speed up conductance?

A

as action potentials only have to be generated in a limited number of spaces, not along the whole length of the axon

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7
Q

How does a wider diameter impact the speed of conductance?

A

will make it faster

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8
Q

Why does a wider diameter speed up conductance?

A

it means that there is less leakage of ions

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9
Q

Why does a higher temperature increase speed of conductance?

A
  • rate of diffusion increases
    -enzymes involved in respiration act faster so more ATP for co-transport
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10
Q

Why would no myelin sheaths lead to slower responses?

A
  • cannot ‘jump’ from node to node
  • more depolarisation over a greater length
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11
Q

How does the myelin sheath impact speed of conductance?

A
  • myelin sheath increases speed of conductance
  • schwann cells cause insulation around an area of the axon
  • depolarisation cannot occur in insulated areas, only in the nodes of Ranvier
  • saltatory conduction
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12
Q

How does temperature impact speed of conductance?

A
  • high temperature increases speed of action potentials
  • higher temperature increases diffusion up until a point
  • enzymes involved in respiration
  • above a certain point enzymes/proteins denature and APs cease
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13
Q

What is the All or Nothing principle?

A
  • threshold value (-55mV)
  • below the threshold, no AP regardless of strength
  • stimulus above threshold will generate an action potential
  • all action potentials are the same size
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14
Q

Why might damage to the myelin sheath of neurones cause muscular paralysis?

A
  • no saltatory conduction/Depolarisation occurs along whole length
  • impulses slowed/stopped
  • do not reach/take longer to reach neuromuscular junction
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