Question

A cell is depolarized when a threshold potential is reached and sodium ions rush into the cell. The depolarization peaks at +30 mV. Na⁺ inflow then abruptly stops, and repolarization begins as potassium ions rush out of the cell. This loss of positive ions causes the membrane potential to become negative again. What happens when a cell is depolarized?

1) The membrane potential becomes positive
2) The membrane potential becomes negative
3) The membrane potential remains the same
4) The membrane potential fluctuates

Answer 1

Depolarization occurs when the membrane potential of a cell becomes less negative or positive. In this case, when a threshold potential is reached, sodium ions rush into the cell, causing depolarization.

Repolarization follows as potassium ions rush out of the cell, making the membrane potential negative again.

Step-by-step explanation:

The depolarization of a cell occurs when the membrane potential becomes less negative or positive.

In the case described, when a threshold potential is reached, sodium ions rush into the cell, causing depolarization and a reversal of the charge across the membrane from -70mV to +30mV.

This change in membrane potential triggers repolarization, where potassium ions rush out of the cell, making the membrane potential become negative again.