Which statement describes the general output of photoreceptors?

Which statement describes the general output of photoreceptors?

• A. They respond to light by adjusting membrane potential.
• B. They produce action potentials that travel along the optic nerve.
• C. They release neurotransmitter in response to light while changing membrane potential.
• D. They are not involved in transduction.

Answer: (C)

Photoreceptors take in light and convert it into an electrical and chemical signal. Their output is a change in membrane potential that modulates neurotransmitter release onto downstream cells. Importantly, they do not generate action potentials; rather, light causes hyperpolarization and a graded change in the amount of neurotransmitter released (glutamate) onto bipolar and other retinal neurons. In darkness they depolarize and release more transmitter; in light they hyperpolarize and release less. So the best description is that photoreceptors output a light-dependent change in membrane potential alongside neurotransmitter release, rather than firing spikes.

Photoreceptors take in light and convert it into an electrical and chemical signal. Their output is a change in membrane potential that modulates neurotransmitter release onto downstream cells. Importantly, they do not generate action potentials; rather, light causes hyperpolarization and a graded change in the amount of neurotransmitter released (glutamate) onto bipolar and other retinal neurons. In darkness they depolarize and release more transmitter; in light they hyperpolarize and release less. So the best description is that photoreceptors output a light-dependent change in membrane potential alongside neurotransmitter release, rather than firing spikes.