all-or-none phenomenon

all-or-none phenomenon

All-or-nothing principle, all-or-none response Cardiac physiology The property of cardiac muscle in which stimulation from a single myocyte travels to the atrium and ventricle before contracting, resulting in a coherent and coordinated pump activity. See Action potential Physiology A rule applied to the activation of individual muscle or nerve cells, where the response to stimuli–depolarization only occurs above a certain threshold, usually –55 mV, after which a complete action potential occurs which is maximum in intensity, ie the strength of the nerve impulse is not dependent on or a function of the strength of the stimulus Psychology A 'soft' rule in behavioral studies, which refers to the observation that a behavioral stimulus will produce either a complete response or none at all.