All-or-nothing law

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The all-or-nothing law describes the phenomenon that a response to a stimulus is either completely triggered or not at all. So there is a threshold that must be exceeded in order to trigger the response. No gradation (differentiation) can be observed in the parameter strength of the reaction, because the reaction to the stimulus always takes place with maximum strength. How strong the stimulus was in the end can only be seen from the frequency of the response curve.

Reason with example

Excitable cells (e.g. nerve cells , heart cells ) communicate via so-called action potentials (parts of the electrical excitation of a nerve cell). In order to trigger an action potential and to achieve a transmission of excitation along the nerve cell, only a critical threshold potential of 15-20 mV has to be exceeded, the intensity of the stimulus strength being of no interest, because this is only determined by the number of action potentials. The more action potentials of a nerve cell are triggered in a defined time unit, the stronger the stimulus that triggers the discharge of a partial area from a certain summation .

From then on, the further depolarization takes place automatically and very quickly. One speaks of a uniform and maximum response in the sense of a transmitted excitement.

Subliminal signals can be amplified by noise and trigger an action potential. This phenomenon is called stochastic resonance .

See also

swell