10.4 Passage of an Action Potential and Speed of Nerve Impulse

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  • Created by: Molly
  • Created on: 10-03-14 12:09
What happens once an action potential has been created?
It moves rapidly along an axon. The size of the action potential does not change at all.
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How does the action potential move?
As one part of the axon becomes depolarised, it acts as a stimulus for the depolarisation of the next region, and in this way the action potentials are regenerated along the axon membrane.
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Why is the passage of an action potential faster along a myelinated sheath?
Because action potentials can occur at the nodes of ranvier and effectively 'jump' from node to node in saltatory conduction.
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How does the myelin sheath affect the passage of a nerve impulse?
Causes the nerve impulse to jump and so is faster.
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How does the diameter of the axon affect the speed of the action potential?
The greater the diameter, the faster the speed of conductance. This is due to less leakage of ions from a large axon.
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How does temperature affect the speed of an action potential?
It affects the rate of diffusion of ions and so higher temperature means a faster nerve impulse.
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What is the refractory period?
A period after an action potential has been created when inward movement of sodium ions is prevented because voltage-gated channels are closed. In this period it is impossible for any more action potentials to be generated.
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What are the 3 purposes of the refractory period?
It ensures that an action potential is propagated in one direction only. It produces discrete impulses. It limits the number of action potentials.
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What is the all or nothing principle?
There is a certain level of stimulus called the threshold value which needs to be achieved for an action potential to be triggered.
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How does an organism perceive the size of a stimulus?
number of impulses passing in a given time, by having different neurones with different threshold values.
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Other cards in this set

Card 2

Front

How does the action potential move?

Back

As one part of the axon becomes depolarised, it acts as a stimulus for the depolarisation of the next region, and in this way the action potentials are regenerated along the axon membrane.

Card 3

Front

Why is the passage of an action potential faster along a myelinated sheath?

Back

Preview of the front of card 3

Card 4

Front

How does the myelin sheath affect the passage of a nerve impulse?

Back

Preview of the front of card 4

Card 5

Front

How does the diameter of the axon affect the speed of the action potential?

Back

Preview of the front of card 5
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