Which statement about rod cells is true?

Which statement about rod cells is true?

• A. They mediate scotopic vision in dim light.
• B. They detect color in bright light.
• C. They provide high-acuity central vision.
• D. They are responsible for pupillary light reflex.

Answer: (A)

Rods are the retina’s high-sensitivity photoreceptors that support vision in very dim light (scotopic vision). Their photopigment, rhodopsin, is extremely light‑sensitive, and many rods funnel their signals onto a small number of ganglion cells. This arrangement boosts detectability in low light but sacrifices spatial detail, so vision is grayscale with poor acuity. Cones, not rods, handle color detection and high-acuity central vision, and they are concentrated in the fovea where rods are sparse. The pupillary light reflex is driven mainly by intrinsically photosensitive retinal ganglion cells (with input from many photoreceptors), not by rods as the primary mediator. So the statement that rods mediate scotopic vision in dim light is the correct one.

Rods are the retina’s high-sensitivity photoreceptors that support vision in very dim light (scotopic vision). Their photopigment, rhodopsin, is extremely light‑sensitive, and many rods funnel their signals onto a small number of ganglion cells. This arrangement boosts detectability in low light but sacrifices spatial detail, so vision is grayscale with poor acuity. Cones, not rods, handle color detection and high-acuity central vision, and they are concentrated in the fovea where rods are sparse. The pupillary light reflex is driven mainly by intrinsically photosensitive retinal ganglion cells (with input from many photoreceptors), not by rods as the primary mediator. So the statement that rods mediate scotopic vision in dim light is the correct one.