What type of potentials do photoreceptors produce?

Photoreceptors, which include rods and cones in the retina, produce graded potentials rather than action potentials. Graded potentials are variations in membrane potential that occur in response to stimuli, and they can vary in size depending on the intensity of the light signal they receive.

When light hits the photopigments in photoreceptors, it triggers a biochemical cascade that leads to hyperpolarization of the cell membrane. This hyperpolarization changes the release of neurotransmitters at the synaptic terminals of the photoreceptor onto bipolar cells, which then transmit the signal. The key characteristic of graded potentials is that they are not all-or-nothing responses; they can be of varying amplitude, which allows photoreceptors to convey information about light intensity effectively.

In contrast, action potentials are fixed, all-or-nothing signals that are typically generated by neurons in response to a threshold level of depolarization. While bipolar and ganglion cells in the retina do generate action potentials, the photoreceptors themselves do not, highlighting why graded potentials are the correct response for this question. Thus, photoreceptors are mainly responsible for creating graded potentials that reflect the varying levels of light exposure.