Which type of receptor adapts most slowly to a sustained stimulus?

• A. Mechanoreceptors
• B. Pain (nociceptor) receptors
• C. Olfactory receptors
• D. Photoreceptors

Answer: (B)

Verified step by step guidance

1. Understand the concept of receptor adaptation: Receptor adaptation refers to the process by which sensory receptors decrease their response to a sustained stimulus over time. Some receptors adapt quickly, while others adapt slowly or not at all.
2. Identify the types of receptors mentioned in the problem: Mechanoreceptors (respond to mechanical stimuli like touch and pressure), Pain (nociceptor) receptors (respond to harmful stimuli), Olfactory receptors (respond to smell), and Photoreceptors (respond to light).
3. Analyze the adaptation rates of each receptor type: Mechanoreceptors and olfactory receptors typically adapt quickly to sustained stimuli, meaning their response diminishes over time. Photoreceptors adapt moderately, depending on the intensity of light.
4. Focus on pain (nociceptor) receptors: Pain receptors are unique because they adapt very slowly or not at all to sustained stimuli. This ensures that the body remains aware of harmful or damaging conditions, which is critical for survival.
5. Conclude that pain (nociceptor) receptors adapt most slowly to sustained stimuli, as their function is to continuously signal potential harm without diminishing the response over time.