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What is the major metabolic fuel of the eye?
What causes Bitot's spots on the eye?
- Vitamin A deficiency
- ultimate lack of mucous so there is more keratin synthesis and deposition in the eye
What metabolic pathway is most active in the eye?
HMP shunt (due to need for NADPH)
What makes up the nucleus of the lens>
Old lens cells that have been compressed together
What are the three crystalline chaperones in the lens?
What causes cold cataracts?
- γ-crystallines are sensitive to cold and will aggregate together.
- **Can be resolved upon heating up
What is Presbyopia?
Loss of near vision
Where does the lens derive its nutrients?
Aqueous humor (since it is not vascularized)
What causes diabetic cataracts?
- Increased glucose in serum enters eye
- Glucose reacts with high Km Aldose Reductase
- Production of Sorbitol
- Increase in eye pressure due to water intake
- **aggregation of lens crystallins
What causes senile cataracts?
- **your eyes continually grow throughout your life, so the crystallines have more chances of aggregation
What is the function of the aqueous humor?
- 1) Pressure for globe-like structure
- 2) nutrients for avascular structures
What cell produces aqueous humor?
What is glaucoma?
- When there is less drainage of aqueous humor fluid with high production of the fluid
- Increased pressure in the eye cuts off blood supply
What is the function of acetazolamide?
Decrease production of carbonic anhydrase to not produce more aqueous humor (HCO3-)
What are the two structures of the retina that differ from the lens and cornea?
- Mitochondria (in inner layers)
What is the photoreceptor pigment in rods?
What is the photoreceptor pigment in cones?
Red, Blue, Green
What is the job of the rods?
Night vision/peripheral vision
What is the job of the cones?
What is the difference b/t the three "opias": 1) Protan 2) Deuteran 3) Tritan
- 1) Protan = red
- 2) Deuteran = green
- 3) Tritan = blue
What is retinitus pigmentosum?
Destruction of rods and then cones. Starts with peripheral/night vision and goes to loss of acute/color vision.
When is neurotransmitter release highest, dark or light?
dark (due to higher Ca2+) in the cell from the cGMP that is open in the outer layer of the rods and cones
Explain light transduction upon shining a light in the eye: (eye normally around -30)
- cGMP gates close and stop any more Na+ and Ca2+ from entering the outer layer
- Na+/K+ ATPase stays open in inner layer and hyperpolarizes the cells to -65
What is produced when light comes in to contact with Rhodopsin?
Explain, with molecules, light transduction:
Light-Rhodopsin = Metarhodopsin-Transducin = GDP-GTP = Alpha subunit dissociates from Beta and Gamma = t-Alpha GTP dissociates two gammas from PDE = PDE hydrolyzes cGMP to 5'GMP which closes cGMP channels = HYPERPOLARIZATION!
What is the most sensitive part of the eye and what is the most congested part within that section?
- Sensitive = macula
- Most congested = fovea centralis
What should be done to avoid macula degeneration?
Intake L and Z molecules in the diet
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