An all-or-none neural response means that a neuron either fires at full strength or not at all.

An all-or-none neural response means that a neuron either fires at full strength or not at all.

• A. Neurons fire only with graded intensity
• B. Neurons vary the strength of their signal
• C. Neurons either fire at full strength or not at all
• D. Neuron fires randomly

Answer: (C)

All-or-none refers to how action potentials work: once a neuron reaches the threshold, it fires a signal with a fixed, full-strength amplitude as it travels down the axon; if the threshold isn’t reached, no action potential occurs. This means the strength of a single neural message isn’t graded by how strong the stimulus is—the signal is either a full spike or nothing. Stronger or weaker stimuli can change how often those spikes occur (the firing rate) or how many neurons are recruited, but they don’t make individual spikes bigger. This is why the option stating that neurons either fire at full strength or not at all is the best description.

All-or-none refers to how action potentials work: once a neuron reaches the threshold, it fires a signal with a fixed, full-strength amplitude as it travels down the axon; if the threshold isn’t reached, no action potential occurs. This means the strength of a single neural message isn’t graded by how strong the stimulus is—the signal is either a full spike or nothing. Stronger or weaker stimuli can change how often those spikes occur (the firing rate) or how many neurons are recruited, but they don’t make individual spikes bigger. This is why the option stating that neurons either fire at full strength or not at all is the best description.