Question

What are the two types of photoreceptors and how do their functions differ?

Answer 1

Hint: The photoreceptors are the pigment-containing cells present in our eye which are responsible for vision. They are present in the inner surface of the retina. These photoreceptors are specialised neuroepithelial cells.

Complete answer:
The photoreceptors in our eye convert the electromagnetic radiations/waves to signals which can stimulate biological processes. These receptors are called neuroepithelial as they are related to neurological functions which are related to signal transduction. There are more than millions of photoreceptor cells present in the retina of the eye.

The two important photoreceptor cells are Rods and Cones. They are arranged irregularly for bringing about proper vision. These cells absorb the light and process them in the brain. The rod cells contain pigment Rhodopsin and cones contain photopsin pigments. The rod cells are responsible for the vision in low light whereas the cones are responsible for colour vision.

Different functions of rods and cones are as follows-

Functions of Rods	Functions of Cones
The rods are distributed throughout the retina thus involved in peripheral vision.	The cones are found mainly in the fovea region so they are involved in centralised vision.
These cells are sensitive to all wavelengths.	These cells are sensitive to blue, green and red wavelengths.
They are responsible for the vision in dim light.	These cells are responsible for coloured vision.

Note: The damage to the photoreceptors can lead to poor visibility. This damage is irreversible. The diseases linked to rods and cones are inheritable and there is no cure for this degeneracy.