Psychology MCAT Practice Exam

What are tonic receptors known for in sensory processing?

1. Detecting changes in stimuli only

2. Generating action potentials as long as stimuli are present

3. Initiating responses to pain stimuli

4. Adapting quickly to constant stimuli

The correct answer is: Generating action potentials as long as stimuli are present

Tonic receptors are specialized sensory receptors that play a crucial role in sensory processing by continuously responding to a stimulus for as long as it is present. This ability to generate action potentials continuously while the stimulus remains leads to sustained information being sent to the central nervous system about the presence of that stimulus. For instance, tonic receptors are responsible for monitoring constant signals such as the position of muscles and joints, which is essential for maintaining posture and balance. Because they do not adapt quickly, they provide ongoing input that is particularly important for functions requiring continuous awareness of changing conditions, such as the feeling of a full bladder or the pressure of a chair against the body. In contrast to tonic receptors, phasic receptors adapt quickly and primarily detect changes, signaling when the intensity of a stimulus first increases or decreases. Thus, the key characteristic of tonic receptors lies in their persistent firing in response to sustained stimuli, reinforcing their critical role in monitoring ongoing conditions rather than just detecting changes.