Which statement correctly describes photoreceptors in the retina?

Which statement correctly describes photoreceptors in the retina?

• A. Sound waves are detected.
• B. They detect photons but are not involved in transduction.
• C. They detect photons and are the only retinal cells capable of photon absorption and electrical transduction.
• D. They regulate vascular blood flow.

Answer: (C)

Photoreceptors are specialized retinal neurons that absorb light and convert it into an electrical signal, starting the process of vision. They contain photopigments (like rhodopsin in rods and photopsins in cones) that detect photons. When a photon is absorbed, the retinal molecule changes shape, triggering a G-protein cascade that lowers cGMP, closes cGMP-gated sodium channels, and hyperpolarizes the cell. This change decreases glutamate release onto downstream neurons, conveying the light information to bipolar and then ganglion cells. This is why the statement that they detect photons and are the only retinal cells capable of photon absorption and electrical transduction is the best description. Other retinal neurons respond to the signal but do not themselves absorb light or perform the primary transduction step. The ideas that photoreceptors merely detect sound waves, or that they regulate vascular blood flow, are not accurate descriptions of their primary function.

Photoreceptors are specialized retinal neurons that absorb light and convert it into an electrical signal, starting the process of vision. They contain photopigments (like rhodopsin in rods and photopsins in cones) that detect photons. When a photon is absorbed, the retinal molecule changes shape, triggering a G-protein cascade that lowers cGMP, closes cGMP-gated sodium channels, and hyperpolarizes the cell. This change decreases glutamate release onto downstream neurons, conveying the light information to bipolar and then ganglion cells.

This is why the statement that they detect photons and are the only retinal cells capable of photon absorption and electrical transduction is the best description. Other retinal neurons respond to the signal but do not themselves absorb light or perform the primary transduction step. The ideas that photoreceptors merely detect sound waves, or that they regulate vascular blood flow, are not accurate descriptions of their primary function.