Depolarization of a cell is caused by an influx of which ion?

Depolarization of a cell occurs primarily due to the influx of sodium ions (Na+). When a cell is at rest, its membrane potential is typically negative, and depolarization is characterized by a shift in this potential towards a more positive value. The process begins when sodium channels in the cell membrane open in response to a stimulus. This allows Na+ ions, which are more concentrated outside the cell, to flow into the cell along their electrochemical gradient.

As sodium ions enter, the interior of the cell becomes less negative (more positive), leading to a rapid change in membrane potential. This is an essential step in the generation of action potentials in neurons and muscle cells, enabling the transmission of electrical signals and muscle contractions. The rise in membrane potential that occurs during depolarization is a crucial aspect of cellular excitability and communication within the nervous system.

The other ions mentioned do not play the same primary role in initiating depolarization. Potassium ions (K+) are more involved in repolarization after a depolarization event. Calcium ions (Ca2+) contribute to various cellular processes including muscle contraction and neurotransmitter release but are not the main drivers of the initial depolarization phase. Chloride ions (Cl-) generally have a