What type of cells are the only two retinal cells that produce action potentials during phototransduction?

The only retinal cells that produce action potentials during phototransduction are ganglion cells and amacrine cells.

Ganglion cells are responsible for transmitting the visual information to the brain via the optic nerve. They generate action potentials in response to the graded potentials they receive from bipolar cells and directly from photoreceptors through synaptic connections. The action potentials created by ganglion cells represent the final output of the retinal processing pathway, encoding visual information for transmission to higher visual centers.

Amacrine cells, although primarily known for their role in modulating the signals between bipolar cells and ganglion cells, can also produce action potentials. They integrate and process signals within the retina, influencing the output of ganglion cells. Their role is crucial for adjusting the responses based on the visual context and contributing to various visual functions such as contrast sensitivity and temporal processing.

This function contrasts with other retinal cells, such as photoreceptors, which primarily produce graded potentials rather than action potentials. Although they initiate the phototransduction cascade that eventually influences ganglion cell activity, they do not generate action potentials themselves. Hence, the combination of ganglion cells and amacrine cells as the only retinal cells capable of producing action potentials during phototransduction is key to understanding how visual