What happens to the membrane charge during depolarization?

What happens to the membrane charge during depolarization?

• A. More anions leave the cell
• B. The membrane becomes impermeable
• C. More cations flood into the cell, increasing positivity until it reaches +30 mV
• D. Potassium leaves the cell

Answer: (C)

Depolarization is when the membrane potential becomes less negative as positive charge builds up inside the cell. This happens because voltage-gated sodium channels open and sodium ions rush into the cell, making the interior more positive. The influx of cations shifts the charge toward positive values, typically rising toward about +30 mV at the peak of an action potential. So, the correct idea is that more cations flood into the cell, increasing positivity. This contrasts with the other possibilities: if more anions left the cell, the interior would become more negative, not depolarized. If the membrane were impermeable, ions wouldn’t move and there would be no depolarization. Potassium leaving the cell would also push the interior toward a more negative potential, contributing to repolarization rather than depolarization.

Depolarization is when the membrane potential becomes less negative as positive charge builds up inside the cell. This happens because voltage-gated sodium channels open and sodium ions rush into the cell, making the interior more positive. The influx of cations shifts the charge toward positive values, typically rising toward about +30 mV at the peak of an action potential. So, the correct idea is that more cations flood into the cell, increasing positivity.

This contrasts with the other possibilities: if more anions left the cell, the interior would become more negative, not depolarized. If the membrane were impermeable, ions wouldn’t move and there would be no depolarization. Potassium leaving the cell would also push the interior toward a more negative potential, contributing to repolarization rather than depolarization.