All-or-none Law
A single nerve fibre will always give a maximum response and producing spikes of the same amplitude when stimulated. If the intensity of the stimulus is increased, the height of the spike always remains the same. In short the propagated impulse in a single fibre cannot be graded by grading the intensity or duration of the stimulus. The nerve fibre gives a maximum response or none at all. This is called the “all or none” principle. It is also Known as all or nothing law. It was first established by the American physiologist Henry Pickering Bowditch in 1871 for the contraction of heart muscle. An induction shock produces a contraction or fails to do so according to its strength; if it does so at all, it produces the greatest contraction that can be produced by any strength of stimulus in the condition of the muscle at the time.This principle was later found to be present in skeletal muscle by Keith Lucas in 1909. The individual fibres of nerves also respond to stimulation according to the all-or-none principle.
