3.6.2.1 Nerve impulses

Question 1

Give one function of the refractory period.

Answer 1

Refractory periods act as time delays between one action potential and the next.

Question 2

What is meant by the ‘all-or-nothing’ nature of action potentials?

Answer 2

An action potential will only activate if the threshold is reached, no matter how big the stimulus is.

Question 3

What is the function of Schwann cells on a neurone?

Answer 3

Schwann cells act as an electrical insulator.

Question 4

Give three factors that affect the speed of conduction of action potentials.

Answer 4

• myelination
• axon diameter
• temperature

Question 5

Explain what causes the change in potential difference from -70 mV to +30 mV.

Answer 5

• A stimulus causes sodium ion channels in the neurone cell membrane to open.
• Sodium ions diffuse into the cell, so the membrane becomes depolarised.