What is the purpose of the refractory period?
Signals are transmitted around the nervous system, along the fibres (axons) of nerve cells, in the form of electrical impulses called action potentials. After an action potential has swept along a single nerve fibre, a second nerve impulse cannot be initiated immediately. Instead a finite time, known as the refractory period, must elapse before another action potential can be generated in response to a further stimulus (such as an electric shock to the nerve). Neurophysiologists sometimes divide this interval into the absolute refractory period, during which a second action potential cannot be elicited, no matter how strong the stimulus, and the relative refractory period, during which a second action potential can be evoked, but only if the stimulus strength is increased. The refractory period sets a limit on the frequency at which action potentials can be conducted along single nerve fibres. In mammals, the absolute refractory period is about 1 millisecond and the maximum firing freq
