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