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40 Cards in this Set
- Front
- Back
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Visible Light Spectrum |
- 400 nm (violet) - 700 nm (red) |
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Optics |
- light rays travel in straight lines - Until it interacts with matter and reflect, absorb, or refract |
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Pupil |
- opening that allows light to enter the eye and reach retina - help focus light rays on retina |
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Iris |
- two muscles that vary the size of the pupil |
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Cornea |
- transparent, external surface of the eye |
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Sclera |
- white of the eye |
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Extraocular Muscles |
- 3 pairs of muscles that attach to sclera -move the eyeball in its orbit |
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Optic Disk |
- pale circular region on retina - origin of blood vessels - optic nerve fibers exit here - blind spot |
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Macula |
- part of the retina for central vision - relative absence of blood vessels
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Image Formation |
- Light is refracted by cornea and converge on retina - Lens refracts light mainly to see close objects, lens hardens with age - image received by retina is inverted - glasses help light rays converge on retina |
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Bipolar Cells |
- synapsed with photoreceptor on one end and ganglion cell on the other |
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Retina Layer Organization |
- Ganglion cell layer (cell bodies of ganglion cell) - inner nuclear cell layer (cell bodies of bipolar cells) - Outer Nuclear Layer (cell bodies of photoreceptors) - Layer of photoreceptor outer segments (light sensitive elements of retina) |
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Ganglion Cells |
- fire APs in response to light - propagates down optic nerve - only source of output from retina |
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Cranial Nerve II |
- Optic Nerve - constitutes ganglion cells |
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Horizontal Cells |
- Receives input from the photoreceptors and project neuritis laterally to influence surrounding bipolar and photoreceptor cells |
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Amacrine Cells |
- Receives input from bipolar cells - Projects laterally to influence surrounding ganglion cells, bipolar cells, and other amacrine cells |
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Photoreceptor Cell |
- Only light sensitive cells in retina |
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Rods |
- long cylindrical outer segment that contains many disks - more sensitive to light - nighttime lighting - all contain same photopigment
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Cones |
- shorter outer segment with fewer membranous disks - daytime lighting - each cone contains one of three types of pigment - See color |
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Photopigment Disks |
- contain photopigment |
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Central Retina |
- Fovea contains only cones - small - lower ratio of photoreceptors to ganglion cells |
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Peripheral Retina |
- higher ratio of rods to cones - higher ratio of photoreceptors to ganglion cells |
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Fovea |
- dark spot center in macula - thinnest part of retina |
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Opsin |
- receptor protein with prebound ligand called retinal in rods - three types sensitive to different colors: blue, red, or green |
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Transducin |
- G-protein -located is disk membrane |
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phosphodiesterase |
- breaks down cGMP |
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cGMP |
- intracellular second messenger |
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Phototransduction in Rods |
- membrane is depolarized (-30 mV) in the dark because cGMP is present and opens Na channels - light changes conformation of retinal, which activates opsin - G-protein transducing is activated, which activates phosphodiesterase - PDE breaks down cGMP, which closes Na channels and hyperpolarizes |
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Phototransduction in Cones |
- 3 types of opsins - perceived color determined by relative activation of 3 opsins |
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Colorblindness |
- cone opsin missing - more prevalent in males - red and green opsin genes located on X chromosome |
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Receptive Field - Bipolar Cells |
- area of retina that when stimulated with light changes the cell's membrane potential - Center-Surround receptive fields: On center/OFF surround; OFF center/ON surround |
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Center - Bipolar Cells |
- received direct input from photoreceptor cells |
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Surround - Bipolar Cells |
- receives input from horizontal cells that provide input from surrounding photoreceptor cellls |
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Receptive Fields - Ganglion Cells |
- center-surround receptor fields - allows for detection of differences in light/ dark across receptive field - detect relative differences in light/dark |
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Types of Ganglion Cells |
- M cells - P cells - nonM-nonP cells |
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M cells |
- Larger cells - Larger Receptive Fields - Detection of Movement - 5% of ganglion cells |
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P cells |
- 90% of ganglion cells - smaller cells - smaller receptive fields - for detection of form and detail - some are color opponent |
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NonM - NonP Cells |
- 5% of ganglion cells - color opponent cells |
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Lens |
- provides additional focusing power, called accomadation |
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Color Opponent Cells |
- Red vs. Green and Blue vs. Yellow receptor fields - M cells have too many photoreceptors with different color opsins to have color opponency |
