all-or-none law

Meaning

A principle stating that the strength of a response of a nerve cell or muscle fiber is not dependent upon the strength of the stimulus, provided the stimulus reaches a threshold.

Examples

• The all-or-none law explains why a neuron does not fire more weakly when the stimulus is barely above the threshold.
• Under the all-or-none law, muscle fibers contract completely or not at all once the excitation threshold is met.