Which type of receptor has the slowest conduction velocity?

• A. Mechanoreceptors
• B. Nociceptors and thermoreceptors
• C. Proprioceptors
• D. Chemoreceptors

Answer: (B)

Conduction velocity in sensory pathways tracks with fiber diameter and whether the fiber is myelinated: thick, myelinated fibers carry signals fastest, while thin or unmyelinated fibers conduct slowly. Nociceptors and thermoreceptors are mainly carried by unmyelinated C fibers, which are small and lack myelin, giving them the slowest conduction. This explains why pain and slow temperature changes often feel gradual or dull rather than immediate. In contrast, mechanoreceptors and proprioceptors use large, myelinated fibers (like Aα and Aβ) for rapid touch, pressure, and position sense, so their signals travel quickly. Chemoreceptors don’t characteristically depend on the slowest fibers, so they aren’t the best fit for the slowest conduction.