Study BIOL 472 Topic Vision Flash Cards

 
Pile Management Card
BIOL 472 Topic Vision

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macular sparing
-lesions at end of path do not affect macula, which has already diverged
-macular sparing tends to occur with lesions beyond the LGB
conjunctiva
-membrane that covers the sclera (white part of the eye) and lines the inside of the eyelids.
color visoin
-similar to rhodopsin, except sensitive to specific wavelengths
-blue cones, green cones, and red cones (sensitive to yellow light)
dark adaptation
-generates more sensitive rhodopsins
light adaptation
-light bleaches photopigments (retinal + opsin)
-sensitivity to light reduced
rhodopsin
2 molecules: opsin (protein embedded in membrane of rod disks)

retinal: vit A derivative
phototransduction
-similar for rhodopsin (rods) and 3 color pigments (cones)

in dark:
-retinal binds snugly to opsin
-cGMP is high
-open Na+ channels
-rod stays depolarized at -40mV
-continuous release f neurotransmitter (glutamte), inhibitoyr for bipolar cells

in light:
-light contacts rod
-rhodopsin changes from cis to trans + opsin
-(similar rxn in cones, but sensitive to blue, green, red wavelengths)
-free opsin activates transducin (G-protein) that activates phosphodiesterase (cGMP to 5'GMP)
-closes Na+ channels
-Na+/K+ ATPase pump dominates
-hyperolarizes to -70mV
-decreases glutamate to bipolar cells
-no more inhibition
occular dominance columns
-alternating right/left eye info projects to cortex
macula
-projects to huge amount of cortex
to oppipital lobe
lateral: top portion of left or right field

medial: bottom portion of left or right field
lateral geniculate body
-in thalamus
-synaspe onto neurons leading to visual cortex in occupital lobe
optic tract
-axonds from nasal (L) and temporal (R)
-lesions affect both eyes
optic chiasm
-asons from nasal retinas cross over
optic nerve
-conducts axons from each eye
lateral or temporal retinas
-central vision
medial or nasal retinas
-peripheral vision
choroid
-pigmented epithelium blood supply
-the vascular layer of the eye lying between the retina and the sclera
pursuit mvt
-eyes remain fixed on moving object and track it
-can't voluntarily do this
-not jerky mvt
saccade mvt
-successive fixation points
-watching telephone poles in cars
-reading
ganglion cells
-W: smallest, rod info, esp. mvt
-X: most common; cone; color info
-Y: largest, least common, rapid mvt, changes in intensity
horizontal cells
-inhibitory to surrounding photoreceptor cells
-determine image representation on ganglion cells
-on center/off surround
-on surround/off center
colors
-blue cone: blue hv
-gren cone: green hv
-red cone: YELLOW hv; we're less sensitive to red
color blindness
-X-linked
-defect in one or more of 3 types of cones
glaucoma
-excess intra ocular pressure
-too much aqueous humor in anterior
cataract
-cloudy lens
astigmatism
-uneven thickness of cornea
presbyopia
-in people >40
-loss of accommodation
hyperiopia
-far sighted
-eye too short
-focal point falls behind the retina
-convex lens correction
-presbyopia in aged lens
myopia
-(near sighted)
-eye too long
-focal point falls before the retina
-concave lens correction
pigmented epithelium
-supplied most of blood
-absorbs excess light rays that escape photoreceptors
-prevents distracting light from reflecting inside the eye
ganglion layer
-axons form optic nerve
-receive info from bipolar cells
order of retina
-blood vessels
-ganglion layer
-amacrine cells
-bipolar cells
-horizontal cells
-rods and cones
-dark pigment epithelium layer
vitreous humor
-much larger chamber than anterior chamber
-clear, gelantinous matrix that helps maintain shape of the eyeball
canal of schlemm
-where aqueous humor normally flows out
-in anterior chamber of eye
-elevated eye pressure usually associated with too much aqueous eye humor
-have to reopen canal of schlemm!
aqueous humor
-fills anterior chamber
-low-protein plasma-like fluid secreted by ciliary epithelium supporting the lens
anterior vs. posterior chambers
-anterior filled with aqueous humor
-small

-posterior filled with vitreous humor
-big
fovea or macula lutea
-cone concentration
-regions of retina with most acute vision
-center of visual field
optic disk or blind spot
-radiates small arteries and veins
-in retina
where neurons of visual pathway form optic nerve (II) and exit the eye
-blind spot
-where optic nerve and blood vessels leave the eye
Accomodation triad
-eyes adjust the shape of lens to keep object in focus

near vision:
-ciliary body contracts
-lens rounds up
-eyes converge
-pupils constricts
relaxed suspensory ligaments

far:
-ciliary body relaxes
-lens flattens
-contracted suspensory ligaments
retina
-light-sensative lining of eye
contains photoreceptors
lens
-bends light to focus it on the retina
-bend incoming light to focus on retina
ciliary body
-contraction alters curvature of the lens
-when contracts, muscle gets round (to see close)
-when dilates, flattens (to see far)
pupil
where light passes through
-changes the amount of light entering the eye
iris
-
sclera
-outer wall of eyeball
-composed of connective tissue
cornea
-where light enters
-transparent disk of tissue on anterior surface
-continuation of sclera
eye muscles
-6 extrinsic eye muscles
eyelids
-close over anterior surface of eye
UV light
-we see 380-760nm
Trigeminal V
-motor to general sensation
-eye, teeth, mouth muscles
-general facial sensation
-three branches on face
Abducens VI
-motor only to lateral rectus
Trochlear IV
-motor only to superior oblique
Oculomotor III
-iris, ciliary body control
-all muscles except superior oblique, lateral rectus
-motor only, to most extrinsic eye muscles
Optic nerve II
-for vision
-only nerve to conduct visual impulses
-sensory only, light sensation
nerves for eye
II
III
IV
VI
V
Vision
-contains photoreceptors
-2 million neurons (more than all other senses combined)
-inverted image on retina
-sends signals to brain
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