The action potential and saltatory conduction

Overview

Recall questions on the resting potential, depolarisation and repolarisation, the refractory period, and why myelination speeds conduction.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Define an action potential.

   Model answer

   A rapid, temporary reversal of the electrical potential difference across the axon membrane.

2. 2

   What is the typical resting potential of an axon and what is the charge distribution?

   Model answer

   At resting potential, the inside of the axon is negatively charged relative to the outside, typically around −70 mV.

3. 3

   How does the sodium-potassium pump maintain resting potential?

   Model answer

   It actively transports 3 Na⁺ ions out of the axon and 2 K⁺ ions into the axon.

4. 4

   Why is the resting axon membrane more permeable to potassium ions than sodium ions?

   Model answer

   Because potassium leak channels are open at rest, allowing K⁺ to diffuse more readily than Na⁺.

5. 5

   What causes depolarisation of the axon membrane?

   Model answer

   A stimulus causes voltage-gated sodium ion channels to open, increasing membrane permeability to Na⁺.

6. 6

   Explain the movement of sodium ions during depolarisation.

   Model answer

   Sodium ions diffuse rapidly into the axon down their electrochemical gradient, making the inside less negative.

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