When Depolarization of the cell membrane occurs when there is a rapid influx (inflow) of?

Depolarization of the cell membrane occurs when there is a rapid influx of sodium ions (Na+) into the cell. This change in membrane potential makes the inside of the cell more positive compared to the outside, which is crucial for initiating action potentials in neurons and muscle cells. The influx of sodium ions typically occurs when voltage-gated sodium channels open in response to a stimulus, leading to the propagation of electrical signals.