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32 Cards in this Set
- Front
- Back
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Cornea |
transparent cover of the front of the eye uneven cover causes astigmatism sclera is the white cover over the eye ball |
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Iris |
muslce that contracts or relaxes to control the amount of light entering the eye |
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Ciliary body |
muscle that controls lens shape |
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Choroid |
vascular layer of the eye |
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Retina |
sensory tissue |
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Optic nerve |
contains the ganglion cell axons that run to the brain contains blood vessels that open into the retina to vascularize the retinal layers |
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The lens |
transparent body located behind the iris a lens that loses its transparnecy is called a cataract cataracts are common in the aged populaiton inverts the image needed to focus the image, suspened by ligaments connected to teh ciliary body amount of contraction of teh ciliary body muscles determines the shape of the lens |
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Presbyopia |
loss of flexibility within the lens produces difficulty focusing on close objects occurs around age of 45 |
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Aqueous humor |
located in the anterior (between cornea and lens)and posterior chamber (between the iris and the lens) |
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Vitreous humor |
between the lens and the retina gelatinous and fills the back of teh eye |
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Retina |
neurons, glia, pigmented epithelium and blood vessels light passes through the lens through the inner layer of ganglion cells and bipolar cells to reach the rods and the cones |
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Photoreceptors |
located distally to the front of the retina so it has to move through the layers of the retain before being recognized |
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Optic disc |
papilla origin of nerve blind spot |
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Macula |
contains the fovea yellow pigmentation of the macular area is known as the macula lutea cones in teh area die which can cause blindness` |
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Retina layers |
photosensors interneurons ganglion cells which are innermost |
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Phototransduction in the dark |
Na and Ca enter the rod cell and causes transmitter release this decreases with light cGMP remains high during the dark which keeps the CNG cation channels open, relies on rhodopsin not being acticvaed |
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Activated rhodopsin |
triggered by light activated transducin activated PDE decrease cGMP decrease positive charge entering decrease AP |
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Cone opsins |
similar to rhodopsin but only absorb light of certain wavelength |
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Cones vs rods |
125 million rods, specialized to function under dim conditions 6.4 mil cones, function in well lit rooms and mediate color |
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Fovea |
lies in the center of the macula central region contains only cones overlying retinal layers are displaced rods are displaced to the peripherary with poor resolution of small objects |
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Retinitis pigmentosa |
hereditary disease of the retina for which there is no cure at present caused by at least 10 different mutations in the phototransduction cascade leads to loss of peripheral bision and can progress to total blindness gene therapy to replace fault rhodopsin gene is in trials |
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Retinal interneuosons |
many photoreceptors synapse onto one interneuron and a single interneuron will synapse on many ganglia and other interneurons |
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Ganglion cells |
about a million cells at least 18 different morph types of the ganglion cell in the human retina changing features in areas of the eye differences convery changes in spatial and temporal contrasts |
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Visual vs receptive field |
visual is the whole area seen by the eye receptive field refers to the part of the visual field that affects a particular visual system neurons |
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Center surround receptive fields |
ON center fires action potential but OFF center inhibits fires fastest if there is a small spot of light centered in the receptive field, responds less to a larger sport of light |
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Off center On surround |
fires when the surround is activated respond best to a small dark spot on a bright background neither type responds welll to an all bright or all dark field |
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Sustained vs transient responses |
sustained will fire during the entire length of the activationg where as transient will fire only a couple times then stop |
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Other ganglion ttypes |
some project to superior colliculus and are involved in eye movement some to suprachiasmatic nucleus that control circadian rhythms |
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Receptive field size |
ganglion cell centers in the fovea and are as small as a fraction of a degree where as the peripheray can be 100 times bigger in the fovea, smaller fields would result in less convergence due to only light in the center of teh receptive field causing activation, high spatial acuity peripherary has photoreceptors with large amounts of convergence, which will allow for the greatest amount of light to be acquired but low sensitivity to spatial resolution |
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Color vision |
Red green center surround is very common blue-yellow used as well if you activated a center green on and red off a large red stimulus will turn off and then fire when removed |
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Color vission |
occurs because located close on X chromosome recombination errors can result in defects |
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Fovea vs peripheray |
sustained, color selective, small field, some on some off center transient, broad band, larger field, mix of on and off center |
