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15 Cards in this Set
- Front
- Back
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What is emmetropia?
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normal vision
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What is farsightedness called?
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Hyperopia
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Where does the image converge in hyperopia? Why?
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behind the retina, because eyeball is too short
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Where does the image converge in myopia? Why?
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in front of the retina, because eyeball is too long
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What is nearsightedness called?
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myopia
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Cell types in the retina? (from outer to inner)
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rods/cones -> (w/modulation by horizontal cells) -> bipolar cells -> (w/modification by amacrine cells) -> ganglion cells -> converge as optic nerve
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How is the light signal transduced into an electrical signal?
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light -> absorbed by rhodopsin in rods/cones -> conformations shift activates G protein cascade -> Na channels CLOSE -> HYPERPOLARIZATION of photoreceptor cell -> STOPS releasing NT
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Which retinal cells fire action potentials?
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ganglion cells only
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What 4 places do ganglion cells project to?
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LGN (majority), suprachiasmatic nucleus of hypothal (circadian rhythms), superior colliculus (saccadic eye mvts), pretectal area (Ed-Westphal/pupillary light reflex)
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Symptoms of 3rd nerve palsy?
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resting "down and out", droopy eyelid, external strabismus (can't focus), mydriasis (dilated pupil), loss of accomodation
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Symptoms of trochlear nerve damage?
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vertical diplopia, difficulty walking down stairs, compensates by tucking chin and looking up slightly, and tilting head away from lesion (to compensate for loss of intorsion)
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Symptoms of abducens nerve damage?
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horizontal diplopia on attempted gaze toward lesioned side
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What is the function of the vestibulo-ocular reflex?
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keep image stationary on retina during head mvts
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What is the function of the optokinetic reflex?
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keep image stationary on retina during visual field motion
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What types of eye movements are used to capture and keep particular stimuli on fovea?
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Saccades, smooth pursuit, fixation
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