What happens at phase C of the action potential?Efflux of Na ions currentInflux of Ca ions currentEfflux of K ions currentInflux of K ion curren

Phase C of the action potential, also known as the repolarization phase, is characterized by the efflux (outflow) of potassium ions (K+). This happens due to the opening of voltage-gated potassium channels and the closing of sodium channels that were open during the depolarization phase (Phase B).

Here's a step-by-step breakdown:

1. At the start of Phase C, the cell has a positive charge due to the influx of sodium ions (Na+) during Phase B.

2. The voltage-gated potassium channels open in response to the positive charge inside the cell.

3. Potassium ions (K+), which are in high concentration inside the cell, start to move out of the cell through these open channels. This is driven by both the concentration gradient (from high K+ inside the cell to low K+ outside) and the electrical gradient (from the positive charge inside the cell to the negative charge outside).

4. As K+ ions leave the cell, they take positive charge with them, causing the cell's interior to become more negative - this is the process of repolarization.

5. Eventually, enough K+ ions leave the cell that the interior becomes negatively charged again, returning to its resting membrane potential.

6. The potassium channels then close, ending Phase C of the action potential.

So, the correct answer to your question is "Efflux of K ions current".