Here you can know about the Physiology of Vision. Also understand the Processes for the Retinal Image Formation and Activation of Photoreceptors. Visit Us: https://bit.ly/31X6A47

1. Fossil Remedies
What is the Physiology of
Vision?

2. Before light can reach the rods and cones of the retina, it must pass
through the cornea, aqueous humor, pupil, lens and vitreous humor.
The first step in Physiology of Vision is retinal image formation and
activation of Photoreceptors. The resulting nerve impulses are then
passed to the visual areas of the cerebral cortex.
RETINAL IMAGE FORMATION:
This requires four basic processes,
 Refraction of light rays
 Accumulation of the lens
 Constriction of pupil
 Convergence of eyes

3. Light rays entering the eye from the air
are refracted at the anterior surface
of the cornea, posterior surface of
the cornea, anterior surface of the lens
and posterior surface of the lens. The
degree of refraction that takes place at
each surface is very precise and such
that rays fall at the fovea centralis.

4. The lens of the eye is Biconvex. Furthermore, it has the unique ability to
change the focusing power of the eye by becoming moderately curved at one
moment and greatly curved the next. This change in curvature of lens is
known as accommodation. In far vision, the ciliary muscle contracts pulling
the ciliary process and choroid forward towards the lens. This causes
shortening, thickening and bulging of the lens and thereby increasing the
curvatures.
Constriction of pupil occurs in response to light reflex involving automonic
nervous system and it is purely the function of smooth muscles of iris i.e.
constrictor or circular muscles of iris.

5. CONVERGENCE IN PHYSIOLOGY OF VISION:
Human eyes are such that they focus on only one set of the object (single
binocular vision). This type of vision is possible due to the phenomenon
called Convergence. Convergence refers to the medial movement of the two
eye-balls so that they are directed towards the object being viewed.
Convergence is the function of the voluntary muscles attached to the outside
of the eye-ball called extrinsic eye muscles. These are superior rectus, inferior
rectus, medial rectus, lateral rectus, superior oblique and inferior oblique.

6. STIMULATION OF
PHOTORECEPTORS:
After the formation of image on the retina, it is
converted into nerve impulses. The steps involved in
the generation of nerve potentials are activation of
rhodopsin and/or iodopsin of rods and cones
respectively.
Hyperpolarization occurs as a result of activation of
these pigments in response to light. These impulses
are then passed through optic nerve to the
thalamus. Here the fibres synapse with other
neurons whose axons pass to the visual areas of the
cerebral cortex located in the occipital lobe. Also
view more useful articles by PCD Pharma Company.

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