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26 Cards in this Set
- Front
- Back
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The eye is composed of what 3 tunics?
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fibrous tunic (superficial)
vascular tunic (middle) nervous tunic (deep) |
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The fibrous tunic includes what 2 parts?
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cornea, and sclera
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What is the cornea's job?
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collects the light rays and bends them for focusing
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What is sclera and its job?
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the white of the eye-provides shape for the eyeball, provides attachment point for extrensic eye muscles
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What 4 parts does the vascular tunic include?
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choroid
lens iris pupil |
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What is the choroid's job?
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darkly pigmented to absorb stray light rays (prevents glare)
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Describe the lens...
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clear(if cloudy=cataract), bends light rays, changes shape to allow for fine focusing
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Describe the iris...
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colored portion of the eye
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Job of pupil?
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controls the amount of light entering the eyeball, radial muscles control pupil dilation
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Unequal pupil dilation indicates what?
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trauma
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The nervous tunic includes...?
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retina
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What is the retina composed of?
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Rods-provide nighttime vision
Cones-provide color vision, not responsive in low light conditions |
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In the visual field..which images stay on the same side as the brain and which images cross over?
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Image on lateral side of retina stay
on the same side as the eyeball Image on the medial sides of the retina cross over to the opposite side of the brain as the eyeball |
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Optic Chiasm is responsible for...?
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the crossing over of visual info.
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In normal vision...?
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eyeball has correct shape and image is focused on the retina
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Describe Myopia...
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(nearsighted)-eyeball is too long, image is focused in front of the retina
cant see far objects corrected by a diverging lens |
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Describe hyperopia...
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(farsighted)-eyeball is too short, image is focused in back of retina
cant see near objects corrected by converging lens |
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Describe astigmatism...
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irregular shape of cornea or lens, causes incorrect refraction of light ray..causing it to disappear
-can change over time -contacts to correct are expensive and need a weight specifically placed |
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Describe the resting state of Dark Current...
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(no light)-Na+ influx into rod leads to neurotransmitter release (glutamate), this inhibits the bipolar and ganglionic neurons so no action potential is generated
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Describe the active state of Dark Current...
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(light needed)-Na+ influx stops due to photobleaching, the neurotransmitter is not released to inhibit the neurons, therefor allowing action potential
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What is the structure of a photopigment?
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Rhodopsin is composed of retinal and opsin. Rods have 1 opsin and cones have 3 opsin.
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Job of retinal in photopigment...
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interacts with lightrays
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Job of opsin in photopigment...
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determines the wavelength of light that retinal absorbs
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Step 1 of photopigments...
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Retinal is initially bent and called cis-retinal, a photon of light 'hits' it and changes it to trans-retinal, a straight form.
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Step 2 of photopigments...
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the trans-retinal seperates from the opsin (photobleaching).
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Step 3 of photopigments...
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the trans-retinal is converted back to cis-retinal during isomerization so that it may join again with opsin.
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