Current Actions

A weak current that can be detected with a sensitive device when any tissue enters an active state (for example, during muscle contraction, secretory activity of a gland, or conduction of an impulse by a nerve) is called action current.

The action current occurs due to a change in the permeability of the cell membrane to sodium, potassium and chlorine ions. At rest, the membrane is permeable mainly to potassium ions, and when the cell is excited, the permeability to sodium increases sharply. This leads to a rapid change in membrane potential and generation of an action current.

The action current plays an important role in the propagation of nerve impulses and muscle contraction. It allows cells to quickly transmit signals over long distances in the body. Measurement of action currents is used in electrophysiology to study excitation processes in nerve and muscle tissue.