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Control and Co-ordination — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYControl and Co-ordination5 Marks
Question
Mechanism of vision.
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Answer

  1. The light rays of visible wavelength pass through the cornea and the lens and are focused on the retina of the eye.
  2. The sight is possible due to conjugated proteins present in the rods and the cones.
  3. These are photo pigments which are composed of opsin (a protein) and retinal (Vitamin A derivative).
  4. The light induces dissociation of retinal from the opsin, which causes a change in the structure of the opsin.
  5. This causes the change in the permeability of the retinal cells.
  6. It generates action potential which is carried via bipolar cells and ganglion cells and further conducted by the optic nerves to the visual cortex (vision centre) of the brain.
  7. The neural impulses are analyzed and the image formed on the retina is thus recognized.

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