All-or-none

All-or-none is a term that refers to a situation in which only two options are available, either all or none. There is no option available in between.

In physiology, all-or-none response of nerves or muscles is either complete response or no response. The strength of such a response of a nerve or muscle fiber is independent of the strength of the stimulus causing it.

All-or-none condition occurs when the strength of the stimulus is above threshold.