Refractory period

Definition

The refractory period is the time interval during which a neuron is unable to fire another action potential. It ensures that each action potential is a separate, all-or-none event and helps maintain the unidirectional flow of nerve impulses.

5 Must Know Facts For Your Next Test

1. The refractory period consists of two phases: the absolute refractory period and the relative refractory period.
2. During the absolute refractory period, no new action potential can be initiated regardless of the strength of the stimulus.
3. In the relative refractory period, a stronger-than-normal stimulus can initiate another action potential.
4. The refractory periods are due to the inactivation and subsequent reactivation of voltage-gated sodium channels.
5. This mechanism prevents the backward propagation of action potentials along an axon and facilitates one-way communication between neurons.

Review Questions

• What are the two phases of the refractory period?
• Why can't a neuron fire another action potential during the absolute refractory period?
• How does the relative refractory period differ from the absolute refractory period?

Related terms

Action Potential: A rapid rise and fall in membrane potential that propagates along a neuron.

Voltage-Gated Sodium Channels: Channels in neuronal membranes that open or close in response to changes in membrane potential, critical for initiating action potentials.

Synaptic Transmission: The process by which signaling molecules called neurotransmitters are released by a neuron to communicate with other neurons or muscles.