Why are action potentials sometimes described as being "all-or-none" in character?
A) The rate of propagation of an action potential down an axon is independent of stimulus strength.
B) They are associated with an absolute refractory period.
C) A supra-threshold stimulus is required to stimulate an action potential during the relative refractory period.
D) An action potential occurs whenever a suprathreshold stimulus occurs, and its amplitude does not vary with the size of a stimulus, as long as the membrane is not in the refractory period.
E) Action potentials are always the same size, even when ion gradients vary in size.

Question

Quizplus · Accepted Answer

An action potential is said to be "all-or-none" because it either occurs or doesn't occur in response to a suprathreshold stimulus, and its amplitude does not vary with the size of the stimulus, as long as the membrane is not in the refractory period. When an action potential is triggered, it always reaches a peak amplitude, then repolarizes to the resting potential, regardless of the strength of the stimulus that initiated it.

Why Are Action Potentials Sometimes Described as Being "All-Or-None" in Character