Retina S2M1

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Retina S2M1
2011-08-12 10:05:54
Ross S2M1

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  1. Fundus
    Only area of teh eye where vessels are directly visible
  2. Electroretinalgram
    Objective measure of retinal transduction
  3. Blood-retina barrier
    Prevents certain drugs and other substance from entering the eye, this is made by Pigment Epithelium derived factor
  4. Retinal hemorrhage
    • Blood vessels leak or rupture in the eye
    • Common in diabetes, high BP, blood disorders, trauma, or aging
  5. Retinal vein occlusion
    • Painless loss of vision
    • Often related to hypertension, elevated lipids, and diabetes
  6. Diabetic retinopathy has what two types
    • Nonproliferative - Small vessel damage causing blurred vision
    • Proliferative - Retinal ischemia stimulates the formation of new vessels causing hemorrhaging and scaring, edema, detachment and loss of vision
  7. Retinopathy of prematurity
    • Abnormal new blood vessel growth, leading cause of childhood blindness in western countries
    • Treated with anit-VEGF and photocoagulation
  8. What is the danger of detached retina
    If not fixed quickly it can cause blindness, it isn't painful so it can be neglected
  9. Transmission of neuronal impulses goes through what cells in the retina
    • Photoreceptors
    • Bipolar neurons
    • Ganglion cells
  10. What is the outer segment of a photoreceptor
    • Site of phototransduction
    • Made of Optic disks
    • Photo pigment molecules embedded in the disks
    • Constantly renewed
  11. What is the inner segment of a photoreceptor cell
    • Supplies energy necessary for the restoration of visual pigments
    • They contain the nucleus and organelles
    • They are connected to the outer segment by a stalk
    • These are not renewed
  12. Rhodopsin
    Photosensitive protein complexes in the outer segment of the photoreceptors
  13. What are the parts of Rhodopsin
    • Opsin
    • - G protein coupled receptor w/ 7 transmem. parts
    • - Transmembrane parts sense the diff. wavelangths
    • Retinal
    • - Vit A derivative
    • - Undergoes conformational changes in light
  14. Photoreceptors don't make an action potential but do make a
    Reaction potential that can be graded
  15. What process happens in photoreceptors when exposed to light
    • They undergo a conformational change from 11 cis-retinal to all trans retinal photopigment
    • Activation of transducin
    • Activation of phosphodiesterase
    • Decreased cGMP
    • Closure of Na+ channels
    • Hyperpolarization
    • Decreased release of synaptic transmitter
  16. What happens to a photoreceptor in the dark
    • 11-cis retinal is bound to opsin
    • cGMP levels are high
    • Na+ channels open
    • Depolarization
    • Increase release of transmitter (Glut)
  17. The Fovea only contains
    Cones there is a 1:1 ratio with ganglion cells here
  18. Where are the rods found in abundance
    Peripheral retina
  19. What is the difference in sensitivity to light between the rods and cones
    • The Rods have a very high sensitivity Cones have a low sensitivity
    • Rods are used most at night
  20. When a dark adapted person moves to light, decomposition is
    Faster then the adaption to dark from light
  21. Rod vision is specialized for
    • Dim light
    • Motion
    • Peripheral vision
    • Not good at detail
  22. Why don't rods provide a sharp image
    • Adjacent rods are connected by gap junctions and share their changes in membrane potential
    • Several nearby rods often share a single circuit to one ganglion
  23. What happens in Vitamin A deficiency
    • Night Blindness
    • Synthesis of retinal is impaired
  24. What happens in Hypervitaminosis A
    Signs of poisoning with nausea, vomiting, headache, dizziness, blurred vision, and loss of muscular coordination
  25. Retinitis pigmentosa
    • Progressive dysfunction of mostly Rods
    • Photoreceptor atrophy
    • Tunnel vision
    • Night blindness
    • Progressive loss of peripheral vision
  26. What is the comparison in prevalence of the different cones
    • Red 64%
    • Green 32%
    • Blue 4%
  27. What are we not born with that gives us the most acute vision
  28. What are the symptoms of Macular degeneration
    • High acuity vision loss
    • Dark spots and cloudiness in central area of vision
    • Yellow depositions (Drusen)
  29. Achromatopsia
    Color blindness (X chromosome)
  30. What is the most common type of color blindness
    Red-green (most common in men)
  31. What is the role of the pigment epithelial cells
    • Light absorption
    • Blood retina barrier
    • Phagocytosis
    • Secretion (growth factors)
    • Vit A storage
  32. Accumulation of lipofuscin (cellular debris) in the retinal pigment epithelium may
    Make retina more sensitive to damage from chronic light exposure
  33. Albinismus causes what symptoms in the eyes
    • Inability to synthesize melanin
    • Light blue eyes (rarely red)
    • Lack of pigment
    • Vision lacks fine details
  34. What makes optical allusions possible
    The eyes detect the contrast of light more then the intensity
  35. Retinal ganglion cell axons are not
  36. Papilledema
    Optic disk swelling that is caused by increased intracranial pressure