How can sensory receptors be classified functionally?

• A. By whether they are encapsulated.
• B. Based on location in the nervous system only.
• C. Based on transduction of stimuli, such as mechanical, light, or chemical changes to the membrane potential.
• D. By whether they are myelinated fibers.

Answer: (C)

Functional classification of sensory receptors is about how they convert stimulus energy into electrical signals. Receptors are grouped by the type of energy they transduce: mechanical energy (mechanoreceptors) from touch, pressure, vibration, and sound; light (photoreceptors) in the retina; chemical changes (chemoreceptors) such as taste, smell, or blood chemistry; and temperature (thermoreceptors). There are also receptors for pain (nociceptors) that can respond to damaging stimuli across modalities. When a stimulus is detected, it creates a receptor potential— a graded change in membrane potential in the receptor cell. If this potential is large enough, it triggers action potentials that travel to the nervous system, conveying the sensory information.

This focus on transduction explains why it’s the best answer: it directly describes the functional mechanism by which sensory information is encoded. Structural traits like whether a receptor is encapsulated, or whether its fibers are myelinated, or where it’s located in the nervous system, describe anatomy or conduction properties but do not define how the receptor interprets and converts the stimulus into neural signals.