Action potentials are described as which of the following?

Action potentials are described as which of the following?

• A. Graded Potentials
• B. Summation
• C. Variable
• D. All or Nothing

Answer: (D)

Action potentials are all-or-nothing events: once the membrane potential reaches a threshold, a complete spike is generated with a fixed, stereotyped amplitude and duration. If the stimulus fails to reach threshold, no spike occurs at all. This means the size of each action potential is essentially the same within a neuron, and stronger stimuli mainly increase how often spikes fire (frequency) rather than making each spike bigger. Graded potentials, in contrast, vary in amplitude and weaken with distance, so they are not all-or-nothing. Summation describes how multiple graded inputs can combine to reach threshold, which then triggers an action potential, but the actual spike itself is still all-or-nothing.

Action potentials are all-or-nothing events: once the membrane potential reaches a threshold, a complete spike is generated with a fixed, stereotyped amplitude and duration. If the stimulus fails to reach threshold, no spike occurs at all. This means the size of each action potential is essentially the same within a neuron, and stronger stimuli mainly increase how often spikes fire (frequency) rather than making each spike bigger. Graded potentials, in contrast, vary in amplitude and weaken with distance, so they are not all-or-nothing. Summation describes how multiple graded inputs can combine to reach threshold, which then triggers an action potential, but the actual spike itself is still all-or-nothing.