Sight relies on which type of receptors?

• A. Photoreceptors
• B. Mechanoreceptors
• C. Nociceptors
• D. Chemoreceptors

Answer: (A)

Detecting light is carried out by photoreceptors in the retina. These specialized cells, rods and cones, transduce light photons into neural signals that the brain can interpret. In darkness they release a steady amount of neurotransmitter; when light arrives, a biochemial cascade reduces the release by causing hyperpolarization of the photoreceptor. This change is then processed by bipolar and ganglion cells, with signals traveling via the optic nerve to the visual cortex for image formation.

Rods are highly sensitive and color-insensitive, helping with night vision, while cones require brighter light and provide color vision and fine detail. The other receptor types—mechanoreceptors for touch and hearing, nociceptors for pain, and chemoreceptors for chemicals—serve different senses and are not primarily involved in vision.