Explain the following
Mechanism of generation of light-induced impulse in the retina
The visible light rays when focused on the retina through the cornea and lens generate potentials (impulses) in rods and cones. The photosensitive compounds (photopigments) in the human eyes, Rhodopsin is composed of opsin and retinal. Light induces dissociation of the retinal from opsin resulting in changes in the structure of the opsin. This causes membrane permeability changes. As a result, potential differences are generated in the photoreceptor cells. This produces a signal that generates action potentials in the ganglion cells through the bipolar cells. These action potentials (impulses) are transmitted by the optic nerves to the visual cortex area of the brain, where the neural impulses are analysed and the image formed on the retina is recognized based on earlier memory and experience.