Class 11 NEET Biology Neural Control and Coordination

(a) : Photosensitive means sensitive to light. The rod cells of retina contain a purplish pigment called rhodopsin. They function in dim light and at night. Rhodopsin consists of a protein component, opsin, linked to a nonprotein chromophore, retinal (or retinene), a derivative of vitamin A. Light falling on the rod is absorbed by the retinal, which changes its form and separates from the opsin component. This initiates the transmission of a nerve impulse to the brain.