Nursing Theories

How do we see? Sense organs contains receptors which detects stimuli.The receives light which it brings to guidance on a layer of light sensitive cells, called the retina.Some of the cells in the retina detect colour.The brain interprets the impulse passed to it from the eyes. The optic centre in the cerebral cortex of the brain produces the picture seen from the nerve impulses.The retina is a thin layer which contains light sensitive cells.These nerves then all pass out of the eye at a point where light sensitive cells argon absent and is so called the blind spot. The way the crystalline lense brings about fine direction is called accommodation. The lens is elastic and its shape and focal length leaven be changed. The focal length of the lens is made all-night for viewing distant objects, by the lens becoming thinner. The suspensory bandage ligament holding thr lens becomes tight, stretching it, due to the relaxation of the ciliate muscles.To view rise objects the ciliary muscles contract.

Long destiny occurs when beneficial objects cannot be tapered because the diverging ray of light atomic number 18 not sufficirntly refracted.Short deal makes distant objects appear blurred because checkout time light ray are refracted too much and cerebrate in front of the retina .With age the natural elasticity o! f the lens is lost so that accommodation is reduced. This condition is called old sight or presbyopia. Should the cornea become uneven, then vision becomes distorted. Parallel vertical or longitudinal bars appear to bend .This is called astigmatism and correction by lenses has to compensate for the uneven cornea.If you want to loll a full essay, order it on our website: OrderEssay.net

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