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Physiology

vision

QuestionAnswer
Cornea shape of cornea has to be perfect, so that light won't bend.
concept thicker the medium, the more it bends light
vitreous humor can bend light as well, but not its primary function
lens bend light more when it's thick and round.
step of light entering the eye light enters cornea, pass through aqueous humor.2. the iris ( smooth muscle) control diameter of pupil for amount of light. in bright light, iris contract to limit the amount of light. in less light iris dilate.
step 3: Accommodation light pass through pupil and hit the lens.4. accommodation, ciliary body control the thickness of the lens to focus light.
Accommodation: distance object For distance of object, light rays are paralleled. 2. lens thins because they don't need to bend light as much.3. Zonules are pulled tight, ciliary would dilate
Accommodation: Near object light rays are divergences( scattered) lens need to be thick to bend light a lot, therefore, zonules slacken and ciliary body contric.
Fovea light focus on fovea as it passes through vitreous humor and hit retina.
Retina contains photoreceptors which embedded in a black pigment epithelial to prevent light from scattering.
Rod Rod is more numerous. located at the outer edges of retina. it function as peripheral vision and dim light.
Cone color vision and visual accuracy. mostly concentrated in fovea. there are three type, green, blue and red.
Retina: photoreceptor outer segment are embedded in pigment epethialium and axon terminal and it synapses to bipolar cell. bipolar cell connects to ganglion cell and to optic nerve.
visual pigment various types, typically rhodopsin,in the outter segment of photoreceptor . it consists of opsin, the structural protein and retinal - vitamine A derivative. when retina changes form, it causes action potential, light travel through optic nerve.
Phototransduction: in the dark no proton of light, retina is in opsin. through G-protein coupled cascade, it opens Na+ gated channel ( Na+ influx) and open K+ ion gated channel (K+ eflux), action potential occurs (excitatory) cause the release of neurotransmitter. Glutamate release.
In light or bleaching Retinal changes conformation, leave opsin and enter pigment epithelium, called bleaching. if bleaching is synchronized, temporary occurs until retinal diffuse back into opsin.
In light Through G-protein cascade, closes Na+ gated ion channel.-photoreceptor hypopolarized (inhibitory), K+ gated ion channel open (K+ eflux only)- prevent the release of glutamate. therefore, no glutamate or less
Two types of bipolar cell because different receptor has different respond to glutamate. Light on bipolar cell is inhibited by glutamate.
Light off light off excited by glutamate
Step 4 of phototransduction ganglion cell receive an info from different bipolar or receptor in different area of retina or visual field. Toward fovea, there's less convergence and high activity.
Binocular Zone an image from each eye. double vision. high activity.
step 5 Ganglion cell send action potential down to optic nerve and crosses at optic chiasm.
step 6 the info is received by the visual cortex in ocipital lope and send info to cerebellum.
Visual defect: Presbyopia Loss accommodation. loss flexibility or ciliary body, loss of contraction
Glucoma is a number one cause of blindness causes by increase ocular pressure that damage optic nerve.most common cause is untreated diabetes. for example, increase glucose in aqueous humor would increase the valume of aqueous humor which then increase the pressure.
color blindness cone type defective
Created by: katzz
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