Photoreceptors sense what?

Photoreceptors sense what?

• A. Sound
• B. Pressure
• C. Light
• D. Taste

Answer: (C)

Photoreceptors sense light. In the retina, rods and cones are specialized cells that detect photons and start the phototransduction process. They contain light-sensitive pigments—rhodopsin in rods and photopsins in cones—that respond when light is absorbed. In darkness, these cells are relatively depolarized due to open cGMP-gated Na+ channels and continually release neurotransmitter onto bipolar cells. When light arrives, the photopigments trigger a cascade that lowers cGMP, closes the channels, and causes hyperpolarization, reducing neurotransmitter release and sending a signal through the retinal circuitry to the brain for visual processing. Sound, pressure, and taste are mediated by other sensory systems (inner-ear hair cells for sound, mechanoreceptors for pressure, and taste receptor cells on the tongue), so photoreceptors are specifically tied to detecting light.

Photoreceptors sense light. In the retina, rods and cones are specialized cells that detect photons and start the phototransduction process. They contain light-sensitive pigments—rhodopsin in rods and photopsins in cones—that respond when light is absorbed. In darkness, these cells are relatively depolarized due to open cGMP-gated Na+ channels and continually release neurotransmitter onto bipolar cells. When light arrives, the photopigments trigger a cascade that lowers cGMP, closes the channels, and causes hyperpolarization, reducing neurotransmitter release and sending a signal through the retinal circuitry to the brain for visual processing. Sound, pressure, and taste are mediated by other sensory systems (inner-ear hair cells for sound, mechanoreceptors for pressure, and taste receptor cells on the tongue), so photoreceptors are specifically tied to detecting light.