Question

lodopsin is a light sensitive (photosensitive) pigment and is present in the
A. Rods
B. Cones
C. Neuroglia
D. Bipolar cells

Answer 1

Hint: The human eyes operate on the same basic principles as a camera. A single lens focuses light from all parts of the visual field onto a sheet of light-sensitive cells. The region of the environment from which each eye collects light rays, is called the visual field.

Complete Answer:
The adult human eyeball is roughly/nearly a spherical structure. The wall of the eyeball is composed of three concentric layers. The external layer is called sclera, middle layer is called choroid and inner layer is called retina.

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 is composed of three layers of cells- from inside to outside-ganglion cells, bipolar cells and photoreceptor cells. There are two types of photoreceptor cells, that is present in the eyes and that are, rods and cones. These cells constitute the light-sensitive proteins called the photopigments.

Now let us collect information about given options:
- Rods: Rods are used chiefly for vision in dim light that is twilight (scotopic) vision is the function of the rods. The rods are made up of a purplish-red protein called the rhodopsin or visual purple. The rhodopsin pigment is incorporated in the membranes of rods.
- Cones: the daylight (photopic) vision and colour vision are functions of cones. In the human eye, there are three types of cones which possess their own characteristic photopigments that respond to red, green and blue light and contain iodopsin protein.
- Neuroglia: neuroglial cells are present in the brain. They constitute about 2/3rd of the brain. These are special cells of neurons but do not contain any kind of protein in it.
- Bipolar cells: these Are actually the cells of the neurons. These bipolar cells can be called bipolar neurons. The bipolar neuron is the world which has one axon or one or more dendrite.

Hence the correct answer is option B.

Note: Cones are of three different types, short wavelength-sensitive (blue) cones, medium wavelength sensitive (green) cones and long wavelength-sensitive (red) cones. The visual pigments for colour vision are: erythrosine (sensitive to red), chloropsis (sensitive to green) and cyanopsin (sensitive to blue). In moonlight we cannot see colours because only the rods are functioning. Due to the low light level cones are not functioning.