Receptor cells in the retina that react to very dim light are called which of the following?

• A. Cone cells
• B. Rod cells
• C. Ganglion cells
• D. Bipolar cells

Answer: (B)

Photoreceptors in the retina come in two main types: rods and cones. Rods are extremely sensitive to light and enable vision in very dim conditions; they use the pigment rhodopsin and can respond to very low light levels, giving us night vision. They are numerous and spread around the periphery of the retina, and they connect to bipolar and then ganglion cells in a way that prioritizes sensitivity over sharp detail. Cones, on the other hand, require brighter light and provide color and fine central vision, concentrated in the fovea. The other two cell types mentioned, ganglion and bipolar cells, are not light-detecting receptors but neurons that transmit and process signals from the rods and cones. So the receptor cells that react to very dim light are the rods.