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Karteikarten

Vision

Anita Klukowska Medicine Englisch 86 Karten

Karten in diesem Stapel (86)

  1. 1What are the 3 types of neural cells in the eyes?Ganglion cells
    Interneurones
    Receptor cells
  2. 2What do retinal ganglion cells (RGC) leave the eye as?As optic tract
  3. 3What is another name for retinal glial cells?Muller cells
  4. 4Where is the retinal layer thicker or thinner?Thicker in the centre, thinner at the periphery
  5. 5Where are the photoreceptors exposed?In the macula lutea, where the inner layer of retina is laterally displaced
  6. 6What is macula lutea?5.5mm wide pigmented area near the centre of the retina which contains fovea centralis at the centre
  7. 7What is fovea centralis?Area of central vision (high- resolution & colour)
    Objects are consistently focused on the fovea
  8. 8What is the 2mm wide area where the sclera has perforations?Lamina cribrosa
  9. 9What is the purpose of lamina cribrosaTo allow the passage of RGC axons and the central retinal vessels
    So called physiological blind spots (no photoreceptors)
  10. 10What is the name for the central depression of the optic disc?Optic cup (1/3 the size of the disc)
  11. 11What happens to the optic disc during glaucoma?Inside- out pressure due to raise in intraocular pressure
  12. 12What happens when intracranial pressure increases?Outside- in pressure
  13. 13What are the 2 seperate circulations for the retina?Choroid vessels from ciliary arteries
    Retinal vessels from the central retinal artery
  14. 14What percentage of the eye has cilioretinal artery?35%
  15. 15What is cilioretinal artery?Anastomosis between choroid and retinal circulation, supplies most of the papillomacular bundle
  16. 16What does the supply of photoreceptors via diffusion depend on?- tight contact between RPE and photoreceptors
    - a permeable Bruch's membrane
  17. 17Where is Bruch's membrane?Between choroid and RPE
  18. 18What is Bruch's membrane?An elastic pentilaminar structure which acts as a molecular sieve and diffusion barrier between the RPE and choroid
  19. 19Is Bruch's membrane involved in chorioretinal diseases, especially age- related molecular degeneration (AMD)?Yes
  20. 20What are the 4 types of photoreceptors?Rods
    L, M and S cones
  21. 21What are the types of interneuroes?2 types of horizontal cells
    12 types of bipolar cells
    30 types of amacrine cells
  22. 22What is the role of horizontal cells?Provide inhibitory feedback onto photoreceptors
  23. 23What is the role of bipolar cells?Extracts a different component from the output of a photoreceptor and transmits it to the inner retina
  24. 24What is the role of amacrine cells?Multiple connectivity (back to bipolar cells, forward to RGC)
    Multiple functions (narrow task specificity, vertical integration, horizontal integration, wide field action)
  25. 25How many types of retinal ganglion cells are there?>17 types
  26. 26How many of them project visual information to the LGN?> 13
  27. 27What do photoreceptors form?Regularly spaced monolayer
  28. 28What are rod cells responsible for?Dark vision & motion
  29. 29What are cone cells responsible for?Colour vision and acuity
  30. 30What are intrinsically photosensitive retinal ganglion cells responsible for?Day: night cycle
  31. 31What are opsins?Universal chemoreceptors
  32. 32What opsin do?Light absorption changes their conformation from resting to a signalling state resulting in a signalling cascade that produces physiological response
  33. 33What is phototransduction?A process of capturing a photon and transforming it into a physiological response
  34. 34Do PR show graded potentials?Yes
  35. 35What is rhodopsin?A membrane protein that consists of 2 parts
    - apoprotein opsin
    - chromophore rtinal
  36. 36What is the visual cycle?A chain of enzymatic reactions that recycle the retinoids used during light detection
  37. 37Why does recycling have to occur in the RPE?PR segments lack necessary enzymes, thus the retinoids have to shuttle across the subretinal space
  38. 38Compare rod opsin and cons opsinsRod and con opsins have the same sensitivity to light, their signalling is different
  39. 39Why rod opsin amplify light responses better than cone opsins?Rod opsins have prolonged signalling in exchange for slower responsiveness
  40. 40What is the consequence of cone opsin responding much faster than rod opsin?Photoreceptors respond much faster
  41. 41Where is L opsin found in terms of genes?On X chromosome
    2/ 3 cones
    Long wavelength
  42. 42Where is M opsin found in terms of genes?On X chromosome
    1/ 3 cones
    Medium wavelenght
  43. 43Where is S opsin found in terms of genes?On chromosome 7
    Short wavelength
    2% of cones
  44. 44Where is rhodopsin found in terms of genes?On chromosome 3
    Medium- short wavelenght
  45. 45Where are L & M opsin found?In fovea centralis
  46. 46Where are S cones found?Outside the fovea centralis
  47. 47Where are rods found?In the outer macula
  48. 48What are colours?Result of calculated cone excitation ratios
  49. 49What are the 3 attributes of colourHure (wavelength)
    Saturation (purity)
    Brightness (intensity)
  50. 50What is colour blindness?A loss or shift in the sensitivity of cone pigments, due to mutations in the OPN1MW> OPN1LW> OPN1SW genes
  51. 51What kind of discrimination is retained?Blue- yellow
  52. 52What are anomalous trichromats?All 3 opsins are present but used in unusual combination to match colours
  53. 53What are protanomalous trichromats?Use more L- opsins than normal individuals
  54. 54What is deuteranomalous trichromats?Use more M- opsin than normal individuals
  55. 55What are true dichromats?One opsin is missing, thus all colours are a match for only two opsins
  56. 56To how many cones that cone bipolar cells connect?Between 1-10 cones
  57. 57What does cone bipolar cells have?On and off types
  58. 58To how many cells does rod bipolar cells connect?To between 30- 50 rods
  59. 59What do rod bipolar cells have?Rod bipolar cells only have an ON types and mainly connect via AII amacrine cells to either ON and OFF cone bipolars
  60. 60How is the output of the photoreceptor encoded?It's encoded into 12 parallel information streams
  61. 61How is the 2D distribution of light intensity expressed?Function of position, wavelength and time
  62. 62How are those streams transmitted?Vertically transmitted to RGCs while being modified by horizontal and amacrine cells
  63. 63What % of RGC axons project to thalamus?90%
  64. 64What % of RGC axons project to subcortical nuclei other than thalamus?10%
  65. 65Describe the visual pathwayThe visual pathway extends from the retina via the dLGN to the calcarine fissure and theraby passes through the entire brain in a transverse orientation
  66. 66What are the 4 divisions of the optic nerve?1. intraocular
    2. intraorbital
    3. intracanalicular
    4. intracranial
  67. 67Through which cistern does the optic nerve pass?Suprasellar cistern
  68. 68What is Chiasmal syndrome?Visual field defect caused by lesions of the optic chiasm, usually caused by pressure upon the middle chiasm from below by pituitary tumours
  69. 69Where is optic chiasm situated?Within circle of Willis, above the pituitary gland, within suprasellar cistern
  70. 70What happens at the optic chiasm?The nasal fibres decussate while the temporal fibres do not
  71. 71What does each emerging tract contain?Contralateral nasal fibres and ipsilateral temporal fibres
  72. 72What does partial decussation allow?Accurate depth perception through stereopsis
  73. 73Why does the primate visual system have higher proportion of ipsilateral retinal projections?Manual activity occurs usually within arms lenght
  74. 74Where does the lateral geniculate body receive extensive modulating connections?Thalamic reticular nucleus
    Layer 6 of visual cortex
  75. 75Describe superior/ dorsal/ direct bundle in terms of visual fieldCarries information from superior retinal quadrant= inferior visual field
  76. 76Describe middle/ central bundle in terms of visual fieldCarries information from fovea centralis= central visual field
  77. 77Describe inferior/ lateral/ anterior bundle in terms of visual fieldCarries information from the inferior retinal quadrant= superior visual field
  78. 78What is Meyer's loop?Part of anterior bundle
    Sweeps back on itself into the temporal lobe
    At risk during temporal lobectomy
  79. 79What are the principles of visual processing?- parallel processing
    - hierarchical
    - functionally & topically segregated
  80. 80How is retinotopic mapping achieved?Parallel pathways from RGC remain anatomically seperate through the LGN and into the primary visual cortex (V1)
  81. 81Where is the primary visual cortex, V1?Broadmans Area 17 (striate cortex)
  82. 82Where is the secondary visual cortex, V2?Broadmans Area 18, 19
  83. 83Are V1 and V2 low level areas?Yes
  84. 84Where are the parallel processing streams that are high level areas located?Beyond V2
  85. 85What is the ventral stream?"What" pathways (colour, form, recognition, long- term moemory
    V1->V2>V4>V8- inferior temporal lobe
  86. 86What is the dorsal stream?"Where" or "How" pathways (action)
    V1->V2->V3>V5/MT (Middle temporal area
    Posterior parietal lobe

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Medicine (FBN) Karteikarten am Vision, erstellt von Anita Klukowska am 28/05/2017.
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