Lecture #22 - The action potential (just Qs)

Question 1

How does an action potential occur? Then what are the steps?

Answer 1

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Question 2

Conduction of an action potential down axon (2 explanations)

1. Relies on…… and
2. Depolarisation during the action potential causes…..

Answer 2

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Question 3

What determines the propagation direction of an action potential?

Answer 3

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Question 4

What are the two refractory periods? Explain ‘em

Answer 4

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Question 5

Refractory periods:

1. Are an in_____ _____ of the ____ ____
2. Depend on the…..
3. “Inactive channels” don’t….
4. What does this prevent?

What’s the activation cycle of a Na+ channel (3)

Refractory periods also limit what?

Answer 5

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Question 6

How to improve conduction velocity of the axon?

Answer 6

Myelination

1. Insulation of the wire (schwaan cells are a type of oligodendrocyte - provide insulating myelin sheath)

Question 7

Unmyelinated vs myelinated axons

Answer 7

Myelinated:

• nodes of Ranvier in between the schwaan cells. These nodes have high density of ion channels so if AP occurs here, the elec field produced is huge and can span distance to the next node.
• The action potential leaps between the nodes of Ranvier so called “saltatory conduction”