Repolarisation

Question 1

Gist

Answer 1

ions begin to diffuse across the membrane back to a polarised state, enabled by the sodium potassium pump and potassium voltage gate channels.

A period of hyperpolarisation occurs as potassium voltage gated channels remain open for longer than needed.

Question 2

Step 1)

Answer 2

Sodiumvoltage gated channels are stimulated to close at +40mV. These channels have an inactive state so the rapid movement of sodium ions into the cell stops immediately.

Question 3

Step 2)

Answer 3

Potassium voltage gated channels are stimulated to open. Potassium ions rushes out of the cell. Sodium-potassium pump is also active.

Question 4

Step 3)

Answer 4

This causes the inside of the cell to become more negative than the outside decreasing membrane potential =repolarisation occurs

Question 5

Step 4)

Answer 5

When the membrane is repolarised to –70mV the potassium voltage gates channels are stimulated to close. Potassium voltage gated channels remain open longer than what is needed so some potassium ions continue to leave the cell for a short period of time until the gates are closed.

Question 6

Step 5)

Answer 6

This results in the membrane potential to drop below its resting state. An undershootoccurs whereby the membrane potential is now greater than –70mV (approx –90mV). The membrane is now said to be hyperpolarised. This increases the refractory period.