Which type of receptor is more likely to respond briefly and then stop firing if a constant stimulus continues?

• A. Tonic receptors
• B. Phasic receptors
• C. Chemo receptors
• D. Mechanoreceptors

Answer: (B)

Phasic receptors are designed to detect changes by adapting quickly to a constant stimulus. They respond with a burst of activity at the moment the stimulus starts and then largely stop firing even though the stimulus continues. This makes them ideal for signaling that something in the environment has changed, rather than conveying information about the ongoing level of stimulation. In contrast, tonic receptors keep firing as long as the stimulus persists, providing continuous information about stimulus intensity. Mechanoreceptors cover a range of behaviors, and chemo receptors respond to chemicals, but the specific pattern described—brief response followed by cessation during a constant stimulus—defines phasic receptors. An everyday example is the initial feeling when you first put on a ring or sweater; you notice it at first, then largely stop sensing it as it becomes familiar.