Chapter 31, Nervous System - Assessment - 31.1 The Neuron - Understand Key Concepts/Think Critically - Page 916: 6

The action potential is considered "all-or-none" because a stimulus either causes an action potential or it doesn't. Either a stimulus reaches the action potential threshold or it doesn't. An action potential is only one size--there are no small or large action potentials.

The action potential is considered "all-or-none" because a stimulus either causes an action potential or it doesn't. Either a stimulus reaches the action potential threshold or it doesn't. An action potential is only one size--there are no small or large action potentials.