Which statement correctly describes phasic receptors?

• A. Slow-adapting, continuously signaling to CNS
• B. Receptors that never adapt
• C. Phasic receptors, which are fast-adapting and may extinguish within a few hundredths of a second
• D. Proprioceptors that provide position sense

Answer: (C)

Phasic receptors respond mainly to changes in a stimulus and then quickly reduce their firing, signaling the onset or offset rather than the ongoing intensity. This fast adaptation means they may extinguish within a very short time, often a fraction of a second, which is exactly what the statement describes. In contrast, receptors that slowly adapt continue signaling as long as the stimulus is present, conveying ongoing intensity rather than rapid change. The idea of receptors that never adapt conflicts with the defining feature of phasic receptors. While proprioceptors provide position sense, that alone doesn’t define phasic behavior, so that option doesn’t capture the rapid, transient response characteristic of phasic receptors.