Question

When light strikes a photoreceptor cell, Na⁺ ion channels __________ , so __________ Na⁺ ions enter the cell, and __________ neurotransmitter (glutamate) is released from the cell.

1) open, more, more
2) open, more, less
3) open, fewer, more
4) close, fewer, more
5) close, fewer, less

Answer 1

The photoreceptor cells respond to light by closing Na⁺ ion channels, leading to a reduction of Na⁺ ion entry into the cell and a decrease in glutamate release. The correct sequence when light strikes a photoreceptor is: channels close, fewer ions enter, and less neurotransmitter is released.

Step-by-step explanation:

When light strikes a photoreceptor cell, Na⁺ ion channels close, so fewer Na⁺ ions enter the cell, and less neurotransmitter (glutamate) is released from the cell. The correct answer is therefore option 5) close, fewer, less. When light activates the photopigment in photoreceptor cells, it leads to a cascade of biochemical events that results in the closure of Na+ channels. This hyperpolarizes the photoreceptor cell and reduces the release of glutamate to downstream neurons. This process is critical for the conversion of light information into electrical signals within the retina.