Question

Explain the mechanism of generation of light-induced impulse in the retina.

Answer 1

1. Retina is the inner layer of the eye.
2. It consists of rods and cones (photoreceptors/visual cells).
3. These contain light sensitive proteins called photopigments.
4. When light rays fall on the retina, potentials are generated in rods and cones.
5. Light induces the dissociation of the photopigments of photoreceptors into opsin (a protein) and retinal (an aldehyde of vitamin A).
6. This results in changes in the three-dimensional structure of opsin.
7. This causes changes in the permeability of the cell membrane.
8. As a result, potential differences are generated in the photoreceptor cells.
9. This produces a signal which generates action potential (impulses) in the ganglion cells.
10. 1These impulses are conducted to the visual area of the cerebrum, via. the optic nerves.
11. 1In the visual cortex area of the brain, neural impulses are analyzed and the image    formed on the retina is recognized based on previous memory