Final answer:
Adaptation is when the action potential frequency declines if the stimulus intensity is maintained at a constant level. An example is the auditory system, where neurons gradually decrease their firing rate when exposed to a constant high-intensity sound.
Step-by-step explanation:
The phenomenon described in the question is known as adaptation or neural adaptation. It occurs when the action potential frequency declines while the stimulus intensity remains at a constant level.
One example of adaptation can be observed in the auditory system. When exposed to a constant sound of high intensity, the firing rate of auditory neurons initially increases, but then gradually decreases over time. This allows the auditory system to filter out repetitive or unimportant stimuli and focus on detecting new or changing stimuli.