The intensity of the stimulus directly affects the intensity of the impulse.

• A. True
• B. False
• C. Not determinable
• D. Depends on neuron type

Answer: (B)

Action potentials are an all-or-none event: once a neuron reaches threshold, the spike that follows has essentially a fixed amplitude. Increasing stimulus strength does not make a bigger impulse in a single neuron. What changes with stronger stimuli is how often the neuron fires (firing rate) and how many neurons are recruited to participate in the signal. In other words, stimulus intensity is encoded by the pattern and number of spikes, not by increasing the size of each spike. So the statement is not correct. Typically, schools teach that stronger stimuli lead to higher firing rates and greater population activity, while the individual impulse remains the same size.