aktionpotentiaali

Aktion potentiaali, often translated as action potential, is a fundamental concept in neurobiology and cell physiology. It refers to a rapid, transient, and regenerative change in the membrane potential of a cell, most notably neurons and muscle cells. This electrical signal is crucial for transmitting information across cells, enabling communication within the nervous system and triggering muscle contractions.

The generation of an action potential is a complex process driven by the movement of ions across the cell membrane. It typically begins with a stimulus that causes a depolarization of the membrane, meaning the inside of the cell becomes less negative. If this depolarization reaches a critical threshold, voltage-gated ion channels, primarily sodium channels, open rapidly. This influx of sodium ions causes a further, rapid depolarization, leading to the rising phase of the action potential.

Following the peak of depolarization, the sodium channels inactivate, and voltage-gated potassium channels open. The outward movement of potassium ions repolarizes the membrane, bringing the potential back towards its resting state. In some cases, the membrane may hyperpolarize, becoming more negative than the resting potential, before returning to its baseline. This entire sequence is an all-or-none event, meaning it either occurs fully or not at all, and it propagates along the cell membrane without diminishing in strength.