What is the action potential threshold?

The action potential threshold refers to the specific level of membrane depolarization that a neuron must reach in order to initiate an action potential. When the membrane potential becomes sufficiently depolarized, typically around -55 mV from a resting potential of approximately -70 mV, voltage-gated sodium channels open, resulting in a rapid influx of sodium ions. This influx leads to a further depolarization of the membrane, ultimately generating an action potential that propagates along the axon.

This threshold is crucial for the all-or-nothing principle of action potentials, where once the threshold is crossed, an action potential is triggered, and if it is not reached, then no action potential occurs. Understanding this concept is essential in neurobiology as it defines the excitability of neurons and the communication between them through electrical signals.