all-or-none law


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Related to all-or-none law: all or none phenomenon, all or nothing response

all-or-none law

1 the principle in neurophysiology stating that a stimulus must be strong enough to reach threshold to trigger a nerve impulse. Once theshold is achieved, the entire impulse is discharged. A weak stimulus will not produce a weak reaction.
2 the principle that the heart muscle or nerve, under any stimulus above a threshold level, will respond either with a maximal strength response or with none at all. Also called Bowditch's law.

all-or-none phenomenon

Cardiology
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 co-ordinated pump activity.
 
Physiology
A rule applied to the activation of individual muscle or nerve cells, where the response to stimuli (depolarisation) only occurs above a certain threshold, usually –55 mV, after which a complete action potential occurs that is maximum in intensity—i.e., the strength of the nerve impulse is not dependent on, or a function of, the strength of the stimulus.
 
Psychology
A “soft” rule in behavioural studies, which refers to the observation that a behavioural stimulus will produce either a complete response or none at all.

all-or-none law

The property in muscle and nerve fibres of either responding wholly to a stimulus or not at all. The strength of the stimulus must exceed a particular threshold or there will be no response, but when the response occurs it is total. The law applies to individual fibres and a graded response is obtained by a variation in the number of fibres activated.

all-or-none law

a law stating that certain tissues respond in a similar way to stimuli no matter how strong the stimuli are, i.e. they either react by giving a response (all), or do not react and give no response (none). Nerve fibres normally act in this way.