Question

Draw a neat and labelled diagram of the vertical section of the eye of man and explain its working.

Answer 1

The light rays entering the eyes are either parallel or diverging when they strike the eyes. In both cases, the light needs to be bent and focussed on the retina. The light rays in the visible wavelength are focussed on the retina through the cornea and the lens. This generates the potential in the rods and the cones present in the retina. The light rays cause the dissociation of the opsin present in both the rods and the cones. This cause the membrane permeability change that generates potential differences in the photoreceptor cells. These cells synapse with the bipolar cells and generate an action potential in them as well. The action potential is passed to the ganglion cells that synapse with the above bipolar cells. The axons of these ganglion cells bundle together to form the optic nerve. Finally, the impulses are transferred to the visual cortex area of the brain through the optic nerve.

After reaching this area, impulses are analysed and an image formed on the retina is recognised. This recognition is based on the earlier memory and experience stored in the brain. This visual cortex area is the part of the occipital lobes of the cerebrum.