15.2: The nerve impulse

Question 1

Nerve impulse

Answer 1

A self-propagating wave of electrical activity that travels along the axon membrane, a temporary reversal of electrical potential difference across the axon membrane.

Question 2

The temporary reversal of electrical potential difference (nerve impulse) is between two states?

Answer 2

Between the resting potential and the action potential.

Question 3

Resting potential

Answer 3

The movement of ions such as Na+ ions and K+ ions across the axon membrane, which is controlled in a number of ways.

Question 4

In what way do Na+ ions and K+ ions move across the axon membrane?

Answer 4

Though protein channels which span the phospholipid bilayer, called ion channels. Of some which have gates and some remain open. Specific channels for Na+ and K+ which can move through the channels by facilitated diffusion.

Question 5

Sodium-potassium pump

Answer 5

Mechanism of the active transport of K+ ions into the axon and Na+ ions out of the axon by protein carriers.

Question 6

Resting potential charge

Answer 6

Inside of the axon is negatively charged relative to the outside, ranges from 50-90mV but usually 65mV in humans. In this condition the axon is said to be polarised.

Question 7

The action potential

Answer 7

A stimulus of a sufficient size’s energy cause a temporary reversal of the charges either side of (a part of) the axon membrane. If the stimulus is great enough, —65mV inside the membrane can become +40mV. = the action potential and in this condition the membrane is depolarised.

Question 8

Why does depolarisation occur

Answer 8

The channels in axon membrane change shape and hence open or close, depending on the voltage across the membrane. They’re therefore called voltage-gated channels.