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PHGY 209 CNS Lecture V

PHGY 209 CNS Lecture V - PHGY 209 CNS-Lecture V November 2...

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PHGY 209 CNS-Lecture V November 2, 2008 Visual perception is context dependent- you don’t see the actual image, but what your brain perceives BASIC ANATOMY OF THE EYE Sclera- outside, white part. (Form a white capsule around the eye, except at the anterior surface where it is specialized into the clear cornea. It protects and shape the eye by providing an insertion point for external muscles that move the eyeball within its socket) Becomes clear at the anterior part-called cornea- in order to let light in. Pupil- opening behind the cornea. The size of the pupil is goverened by the iris ( muscles on the iris determine the diameter of the pupil opening that allow light into the eye) Lens- sit behind the pupil- focus the light. Cornea also focus the light. ( Cornea plays a larger quantitative role than the lens in focusing light wave due to waves refracted more in passing from air to the cornea than when they are passing into and out of the lens) Viterous humor- clear jelly (Between the lens and the retina) Retina- lines the back half of the eyeball. (extension of the brain lining the inner posterior end of the eye- contain numerous types of neurons as well as photoreceptors) Chloroid- behind the retina absorb scattered light (don’t want light to bounce around and distort your vision-some animals like cat have very reflective chloroid) ( darkly pigmented) Optic nerve- send information to your brain about the visual world Blood vessels on the retina- where the blood vessels are, you don’t see anything. Forvea centralis- central part of the retina highest visual acuity highest concentration of photoreceptors Optic disk- where the optic nerves leave the retina. No photoreceptors here. Brain fills in the information here. OPTICS OF THE EYE Refraction-bending of light when it travels from one medium to another. Amount of refraction depends on the angle of incidence as well the properties of the two mediums.
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