toimintav

Toimintav is a Finnish term that translates to "action potential" in English. It refers to a rapid and transient change in the electrical potential across the membrane of a neuron or muscle cell. This electrical signal is the fundamental mechanism by which these cells communicate and transmit information.

The generation of an action potential is a complex process involving the movement of ions across the cell membrane. When a cell receives a stimulus, ion channels open, allowing sodium ions to rush into the cell. This influx of positive charge causes the membrane potential to become more positive, a phase known as depolarization. If the depolarization reaches a certain threshold, it triggers a rapid and irreversible cascade of events.

Following depolarization, voltage-gated sodium channels inactivate, and potassium channels open, allowing potassium ions to flow out of the cell. This outflow of positive charge repolarizes the membrane, returning it to its resting potential, and in some cases, leading to a brief hyperpolarization where the membrane potential becomes even more negative than the resting potential. The action potential then propagates along the axon of a neuron or the muscle fiber, enabling the transmission of signals throughout the nervous system and triggering muscle contractions.