5.1.1 Action Potential

Question 1

What are the 4 stages in order of action potential?

Answer 1

• Depolarisation
• Repolarisation
• Hyperpolarisation
• Resting potential.

Question 2

What happens at the depolarisation stage?

Answer 2

• High sodium ion concentration outside of the cell due to active transport by sodium-potassium pumps during resting potential.
• The ‘first’ sodium ion channels open by the small energy, but that energy is not enough to open the subsequent voltage-gated sodium channels.

Question 3

What happens at the repolarisation stage?

Answer 3

• At 40mV, these voltage-gated potassium channels open meaning, more channels available for more potassium ions to leave the cell through facilitated diffusion.

Question 4

What happens at the hyperpolarisation stage?

Answer 4

• Potassium channels are slow to close, so there’s a slight overshoot where two many potassium ions diffuse out of the neurone.
• Potassium channels close.

Question 5

What happens at resting potential?

Answer 5

• Resting potential is then restored by sodium-potassium pump.