All-or-none law

It was first established by the American physiologist Henry Pickering Bowditch in 1871 for the contraction of heart muscle.

[2] The first recorded time of isolating a single action potential was carried out by Edgar Adrian in 1925 from a set of crosscut muscle fibres.

Using a thermionic triode valve amplifier with 1850 amplification, Adrian noticed that when the muscle preparation was left to hang, it produced oscillations; yet when supported, no such activity occurred.

Stimulus strength was manipulated and the resulting frequency measured, yielding a relationship where f∝sn [further explanation needed].

[4] The magnitude of the action potential set up in any single nerve fibre is independent of the strength of the exciting stimulus, provided the latter is adequate.

If a nerve trunk is stimulated, then as the exciting stimulus is progressively increased above a threshold, a larger number of fibres respond.