Final answer:
When positive charges flow into the cell, the cell undergoes depolarization.
Step-by-step explanation:
When a stimulation causes positive charges to flow into the cell and the membrane potential of the cell becomes more positive, the cell has undergone depolarization.
During depolarization, the cell membrane becomes permeable to Na+ ions, which rush into the cell due to both diffusion and the Coulomb force. This influx of positive ions neutralizes the inside membrane and makes it slightly positive. As a result, the membrane potential becomes less negative or even positive.
Overall, depolarization is an essential step in generating an action potential, which is a voltage pulse that allows nerve cells to transmit electrical impulses and communicate with other cells.