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Visual Systems

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What happens embryologically on day 25?
the edges of the neural fold comes together, the neural ectoderm comes into close contact with surface ectoderm
The retina and optic nerve develops as an outpocket of what?
the diencephalon
What does the optic vesicle cuase?
the differentialtion of the overlying surface ectoderm to form the lens placode
What does the lens placode give rise to?
the lens vesicle
What will the lens vesicle form?
the primitive lens
What happens to the optic vesicle?
it invaginates and forms the 2-layer optic cup
What are the two layers of the cornea derived from?
outer-surface ectoderm
inner-neural crest cells
what do the iris and the ciliary process form from?
the outer rim of the optic cup
What are the components of the external layer?
sclera, cornea (avascular, densely innervated by V)
What are the components of the middle layer?
choroid capillaries, ciliary body, stroma of iris
What are the components of the inner layer?
retinal pigment epithelium and the neural retina
What produces aqueous humor?
ciliary body
What are the boundaries of the anterior chamber?
the cornea and the iris
What are the boundaries of the posterior chamber?
iris and lens
What are the boundaries of the vitreous body?
lens to retina
What mediates accomadation?
the capsule surrounding the lens
Which cells are responsible for the production of the new lens cortical fibers?
E-cells
What is the state of the ciliary muscle need to see in the distance?
relaxed, lens is thin and the curvature is reduced
What is the state of the ciliary muscle needed to see near?
contracted, lens is relaxed with greater curvature
What is myopia?
optical power of the lens is abnlly strong
How do you correct myopia?
concave, diverging lens
What is hyperopia?
optical power is abnlly weak
How do you correct hyperopia?
converging, convex lens
What is a stigmatism?
optical power of the lens is heterogenous
How do you correct astigmatism?
cylindrical lens
What is amblyopia?
visual deficit in one eye
What does amblyopia cause?
cataract, ptosis, strabismus, refractor errors
The cornea uses what type of metabolism?
aerobic
The lens uses what kind of metabolism?
anerobic
What is the function of the retinal epithelium?
metabolically supports photoreceptors and forms blood-retinal barrier
What are the two classes of the ganglion cell?
Large Y and Small X
What is the function of the large Y ganglion cell?
movement of light
What is the function of the small X ganglion cell?
color discrimination
Where do the Large Y cells project to ?
Magnocellular of LGN
Where do the Small X cells project to?
Parvocellular of LGN
When are rods responsive?
moonlight levels of intensity
What is the pigment associated with rods?
Rodopsin
What does a photon do to Rodopsin?
it isomerizes it to metarodopsin II
What happnes to 11-cis-rentinal?
it is converted to all-trans retinal
What does metarodopsin II do?
it activates tranducin
What does transducin do?
it decreases cGMP levels
What happens when cGMP levels dec?
it closes cGMP-gated ion channels, hyperpolarizing the PR
What happens when the PR is hyperpolarized?
it releases less glutamate
What myelinates optic nerver?
oligodendrocytes
What would happen if the optic nerve was lesioned?
one whole eye would be blind
What does a pituitary tumor cause?
bitemporal heteronymous hemianopsia
Where do 10% of the fibers from the retina go?
superior colliculus
Which layers of the LGN do the parvocellular ganglion cells project to?
outer 4 laminae
Where do the magnocellular ganglion cells project to?
inner 2 layers
Which lamina receive from ipilateral eye?
2,3,5
Which lamina receive from contralateral eye?
1,4,6
What should you think when there is macular sparing?
cortical lesion

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