Question

Which one is the correct difference between rod and cone cells?

| | Rod cells | Cone cells
---|---|---|---
(A) | Overall function | Vision in poor light | Colour vision and detailed vision in bright light.
(B) | Distribution | More concentrated in centre of retina | Evenly distributed all over the retina.
(C) | Visual activity | High | Low
(D) | Visual pigment | Iodopsin | Rhodopsin

Answer 1

The inner coat of the eyeball is the retina. It contains the actual light receptors, the rods and cones, and thus retina functions in the same way as the film of a camera does. Retina contains three layers of cells- from inside to outside-ganglion cells, bipolar cells and photoreceptor cells. There are two types of photoreceptor cells, namely, rods and cones. These cells contain the light-sensitive proteins called the photopigments.

Complete answer:

| Rod cells | Cone cells
---|---|---
Number of cells | They are more in number | They are less in number
Pigment present | They have rhodopsin in them | They have Iodopsin in them
Type of vision | They give response to dim light that is give vision in poor light | They give detailed and colour vision and operated in bright light
Distribution | They are distributed at periphery of retina | They are distributed at centre of retina
Speed of response to light (visual activity) | They give slow response (low) | They give fast response (high)
Size | They are small | They are large
Number of visual pigment | Only one pigment is present | Three visual pigments are present.

According to above mentioned differences the correct option is a) that rod cells function is vision in poor light and cones colour vision and detailed vision in bright light.

Note: The visual pigments for colour vision are: erythrosine (sensitive to red), chloropsin (sensitive to green) and cyanopsin (sensitive to blue). In moonlight we cannot see colors because only the rods are functioning. Due to the low light level cones are not functioning, And the sensations of different colours are produced by various combinations of these cones and their photopigments. When these cones are stimulated equally, a sensation of white light is produced.