**2. Brief description of photoreceptor**

The photoreceptors are the only cells that can convert incoming light into an electrical signal that can be carried to the brain (via the optic nerve) to generate conscious vision. Photoreceptors (rods and cones) are highly polarized and specialized neurons with distinct compartments: cell body, inner segment (IS), and outer segment (OS). Although both rods and cones share a similar overall arrangement of the different compartments, they are diverse in their shape, size, and light-detecting capacities. Rods are highly sensitive to light (only active in starlight vision at night) and show long cylindrical structures with the ciliary OS membrane including many membranous discs, which are loaded with the photopigment rhodopsin and other proteins that participate in the phototransduction cascade.
