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Flashcards by Alexandra Levy, updated more than 1 year ago
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Created by megdouglask
about 9 years ago
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Copied by Alexandra Levy
about 7 years ago
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| Question | Answer |
| PHOTORECEPTORS | Photoreceptors are specialised cells located in the retina: rods and cones. The rods are the most sensitive to light and dark changes, shape and movement. Cones control the colour vision aspect of sight. |
| CONCAVE LENS | Causes light rays to spread apart or diverge. |
| CONVEX LENS | Causes light rays to meet or converge. |
| REFRACTION | A change of direction that light undergoes when it enters a medium with a different density from the one through which it has been traveling. |
| CILIARY BODY | The ciliary body is the structure in the eye that releases aqueous humor within the eye. The ciliary body also contains the ciliary muscle, which changes the shape of the lens when your eyes focus on something. |
| RETINA | Light sensitive membrane located at the back of the eye which translates light rays into nervous signals. (Continuous with optic nerve) |
| CORNEA | The transparent layer that forms the front of the eyeball. |
| CHOROID | The choroid is the vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera. |
| VITREOUS HUMOR | A jelly-like fluid that maintains the shape of the eye. Located behind the lens inside the choroid. |
| AQUEOUS HUMOR | A watery fluid that maintains the shape of the eye. Located between the cornea and the lens. |
| CONJUCTIVA | A continuation of the epidermis of the skin; protects the cornea at the front of the eyeball against friction. |
| SCLERA | The white of the eye, a tough coat of fibres; protects the eyeball against mechanical damage, maintains shape of eyeball. |
| ELECTROMAGNETIC SPECTRUM | Consists of waves of varying wavelengths. These waves include visible light, infra-red radiation and ultraviolet radiation. Blue-green light is the most effective wavelengths for humans. Either side of this wavelength in the red and ultraviolet areas are less effective in humans but are used by other organisms. |
| HYPEROPIA | Long-sightedness. People with hyperopia see objects in the distance clearly but close objects are out of focus. Rays from distant objects are focused behind the retina not on the retina. The eyeball is too short or the lens gradually hardens with age, reducing its power of accommodation. |
| MYOPIA | Short-sightedness. People with myopia see objects that are close clearly but objects in the distance are out of focus. Rays from distant objects are focused in front of the retina not on the retina. The usual cause of myopia is that the eyeball is too long. Some forms of myopia improve with age. |
| CATARACTS | Cataracts are a clouding of the lens resulting in blurred or patchy vision. |
| RHODOPSINS | Rhodopsins are light-sensitive pigments, which consist of two molecules bonded together, opsin and retinal. When light enters a rod cell, it splits rhodopsin molecules into its two components. Rods contain rhodopsin sensitive to blue-green light. |
| COLOUR BLINDNESS | Colour blindness in humans occurs because one or more of the three types of photopigments in cones is either absent or does not function properly. |
| PHOTOPIGMENTS | Photopigments are unstable pigments that undergo a chemical change when they absorb light. |
| IRIS | A thin, circular structure in the eye, responsible for controlling the diameter and size of the pupil and thus the amount of light reaching the retina. The color of the iris gives the eye its color. |
| PUPIL | A transparent hole located in the centre of the iris that allows light to strike the retina. |
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