Bio30 Chapter 12.2 - Photoreception
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22 terms
Terms | Definitions |
|---|---|
 Sclera | The white, tough, fibrous protective layer that gives the eye its shape |
| Cornea | The transparent part of the sclera at the front of the eye, through which light enters |
| Choroid | Vascular membrane of the eye that lies between the retina and the sclera; absorbs stray light rays that are not detected by the photoreceptors in the retina |
| Iris | The doughnut-shaped, coloured muscle formed from the choroid at the front of the eye; adjusts the central dark pupil to regulate the amount of light that enters the eye |
| Pupil | Aperture in the middle of the iris of the eye, whose size can be adjusted to control the amount of light entering the eye |
| Adaption | In vision, the process by which the iris adjusts the size of the pupil based on the light conditions, thereby controlling amount of light that enters |
| Retina | The innermost layer of the eye, containing the photoreceptors (rods and cones) |
| Rod | Type of photoreceptor in the eye that is more sensitive to light intensity (level of brightness) than is a cone, but is unable to distinguish colour |
| Cone | The type of photoreceptor in the eye that is sensitve to different colours |
| Optic Nerve | A nerve that carries messages from the photorecepotors in the retina to the brain |
| Aqueous Humour | Clear, watery fluid in anterior chamber of eye; maintains the shape of the cornea and provides oxygen and nutrients for the surrounding cells, including those of the lens and cornea |
| Glaucoma | Condition caused by blockage of the draining of aqueous humour in the eye; resulting pressure ruptures delicate blood vessles in the eye and causes deterioration of the cells due to a lack of oxygen and nutrients, can lead to blindness of untreated |
| Vitreous Humour | A clear, jelly-like fluid inside the posterior chamber of the eye; helps to maintain the shape of the eyeball and support the surrounding |
| Lens | Clear, flexible part of the eye that focusees images in the retina |
| Accommodation | In the eye, adjustment that the ciliary muscles make to the shape of the lens to focus on objects at varying distances |
| Cataract | Cloudy, or opague, grey-white area on the lens of the eye caused by the degeneration of the protein structure of the lens; prevents the passing of light; increases in size over time and can lead to blindness if not medically treated |
| Astigmatism | Uneven curvature of part of the cornea or lens that results in uneven focus and therefore blurry vision |
| Myopia | Near-sightedness, or difficulty seeing things that are far away; caused by ciliary muscles that are too strong or an eyeball that is too long |
| Hyperopia | Fair-sightedness, or difficulty seeing things that are nearby; caused by weak ciliary muscles or an eyeball that is too short |
| Fovea Centralis | Concentration of cones on the retina; loacted directly behind the centre of the lens |
| Colour Blindness | An inherited condition that occurs more frequently in males than in females; is actually colour deficiency, caused by a lack of particular cones, usually red and green cones (thus, a red-green colour-blind person may find it difficuly or impossible to know the difference) |
| Blind Spot | Region of the retina lacking photoreceptors (rods or cones) and where the optic nerve leaves the eye; is incapable of detecing light |
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