Which ion movement is responsible for the restoration of the resting membrane potential after depolarization?

The restoration of the resting membrane potential after depolarization is primarily due to the movement of potassium ions. After a depolarization event, which is often initiated by the influx of sodium ions, the membrane potential becomes more positive. In order to return to its original resting state, potassium channels open, allowing potassium ions to flow out of the cell.

This efflux of potassium is driven by both the concentration gradient and the electrical gradient, as the inside of the cell becomes more positively charged during depolarization. The movement of potassium ions out of the cell helps to re-establish the negative charge inside the cell, effectively bringing the membrane potential back to its resting value.

While calcium influx and sodium efflux play roles in various cellular processes, they do not contribute to the re-establishment of the resting membrane potential following depolarization in the same way that potassium efflux does. Chloride efflux also does not have a significant role in this context. Thus, the primary mechanism for restoring the resting membrane potential is the outward flow of potassium ions.