The action potential

Electrical signals are propagated over the plasma membrane of electrically excitable cells by electrical events called action potentials. During the action potential, the membrane depolarizes briefly before repolarizing to the resting condition (Fig. 3.18.1). The depolarizing phase of the action potential is generated by an increase in membrane permeability to Na⁺ through the opening of voltage-gated Na⁺ channels. The flow of Na⁺ inwards, down its electrochemical gradient, drives the membrane potential towards the equilibrium potential for Na⁺ (E_Na), thereby depolarizing the membrane. Soon after activation, Na⁺ channels pass from an open to an inactivated conformation, reducing the rate of Na⁺ influx back to resting levels

Fig. 3.18.1 The action potential.

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