Explain the mechanism of vision.
Mechanism of vision :
The light rays from the object pass through the cornea and the lens. These are focused on the retina of the eye. The rods and the cones contain photopigments which are conjugated proteins. They are composed of opsin and retinol. The light induces dissociation of retinol from the opsin resulting in changes in the structure of opsin. This causes a change in the permeability of retinal cells. It generates an action potential which is carried via bipolar neurons and ganglion cells and further conducted by the optic nerves to the visual cortex of the brain. The neural impulses are analyzed and the image formed on the retina is recognized.