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Eyes, ears, nose, and throat
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Photoreception is the process that describes how photoreceptors like rods and cones absorb light waves that enter the eye and convert them into electrical signals which are then sent to the brain for visual processing.
The retina itself is composed of ten of its own distinct layers.
Moving from the deepest layer of the retina, from posterior to anterior, the layers are as follows: the pigment epithelium, the photoreceptor layer, the outer limiting membrane, the outer nuclear layer, the outer plexiform layer, the inner nuclear layer, the inner plexiform layer, the ganglion cell layer, the nerve fiber layer, and finally the inner limiting membrane.
Since the inner limiting membrane and nerve fiber layer are the most anterior portions of the retina, you would think that as light enters the eye it would hit these layers first.
However, light actually travels right past all the retinal layers until it comes into contact with the deepest layer of the retina, the pigmented layer.
So let’s trace the pathway of a visual impulse as it travels from the pigmented layer, all the way through to the nerve fiber layer and eventually to the brain.
The pigmented layer contains epithelial cells which absorb light so it doesn’t scatter within the eye.
Photoreceptors are specialized neurons that detect light and when they hyperpolarize, they send visual impulses in the form of electrical signals to the brain.
Photoreception is the process by which photoreceptor cells transduce light energy into electrical energy. Human photoreceptor cells are rods and cones found within the retina. Rods are mainly used for night vision, have a high sensitivity to light, and a low visual acuity, whereas cones are mainly used for color vision, have a low sensitivity to light, and a high visual acuity.
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