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प्रश्न
Explain the following:
Mechanism of generation of light-induced impulse in the retina.
उत्तर
Retina is the innermost layer of the eye. It contains three layers of cells – inner ganglion cells, middle bipolar cells, and outermost photoreceptor cells. Photoreceptor cells are composed of a protein called opsin and an aldehyde of vitamin A called retinal. When light rays are focused on the retina through the cornea, retinal gets dissociated from opsin. As a result, the structure of opsin gets changed. This in turn causes the permeability of the membrane to change, thereby generating a potential difference in the cells. Consequently, an action potential is generated in the ganglion cells and is transmitted to the visual cortex of the brain via the optic nerves. In the cortex region of the brain, the impulses are analysed and the image is formed on the retina.
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संबंधित प्रश्न
Write the function of retina in human eye.
Explain the mechanism of vision.
Name the part of the eye:
which changes the focal length of eye-lens.
Where is the image formed in a human eye?
What is the range of vision of a normal human eye?
Give the scientific names of the following parts of the eye:
muscles which change the shape of the eye-lens.
Fill in the following blank with suitable word:
To bring light from a distant object to a focus on the retina of the eye, the convex eye-lens needs to be made..........
The descriptions of five kinds of images are given below:
(a) diminished and virtual
(b) enlarged and real
(c) enlarged and erect
(d) real and inverted
(e) virtual and the same size
Which one of these describes the image formed:
(i) on the retina of the eye?
(ii) by a magnifying glass?
(iii) by a convex driving mirror on a car?
(iv) by a plane mirror?
(v) on the screen of a slide projector?
What shape are your eye-lenses:
when you look at your hand?
When is a person said to have developed cataract in his eye? How is the vision of a person having cataract restored?
Which of the following have a wider field of view?
(a) Animals having two eyes on the opposite sides of their head.
(b) Animals having two eyes at the front of their head.
With reference to the functioning of the eye, answer the question that follow:
Name the cells of the retina and its respective pigments which get activated in the dark.
We see advertisements for eye donation on television or in newspapers. Write the importance of such advertisements.
Choose the correct answer.
Which one is the photoreceptor _____________
Mention, if the following statement is True or False
The least distance of distinct vision for the human eye is 25 cm
State the Function:
Aqueous humour
We cannot distinguish colours in dim light. Explain giving suitable reasons.
The change in the focal length of an eye lens in human beings is caused by the action of ______.
With reference to human eye, answer the following question.
What is blind spot?
Assertion (A): Rods and Cones are photoreceptors in the sclera of eyeball.
Reason (R): Rods are sensitive to dim light.
