1.6 Vision Sense

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1.6 Vision Sense
2015-01-23 14:46:17

Physiology of vision
Show Answers:

  1. The eyes work like a camera..
    It retracts and focuses light rays to form image on retina
  2. Which portion of the eye is the part that retracts & focuses?
    Anterior protion
  3. Which portion of the eye is the part that transduces the image?
    Posterior portion
  4. The eye can detect wavelengths from which range?
    400-700 nm
  5. What occurs when light rays hit a curved surface?
    The light rays will bend
  6. Light rays AND convex surface
    Light rays hit convex surface and they will bend inwards creating a focal point then spread out creating an upside down image
  7. Light rays AND Concave Surface
    • Light rays hit the concave surface and do not create a focal point, instead they end up diverging further more.
    • *not useful for human eye
  8. Which surface is useful for human eye?
    Convex surface
  9. 2 structures that retract light

  10. What type of surface does cornea contain?
    Convex surface
  11. Why does the cornea contain low water content? And how does this occur?
    If it has a high water content then it would blur the image.

    The lower water content is maintained by a sodium pump
  12. Which structure bends the light more?
  13. What type of surface does the lens have?
    Convex surface
  14. Does the lens have low water content or high?
    Low water content
  15. What are the lens held by?
    suspensory ligaments that surround the lens In a circle
  16. What are the suspensory ligaments attached to?
    ciliary muscles
  17. Focusing on something is the active process of ..
    Bending the light in a way to properly view it
  18. What occurs when ciliary muscles contract? (3)
    -ciliary muscles pull forward

    -relaxes ligaments

    -causes lens to become more globular
  19. What occurs when ciliary muscles relax? (2)
    -pulls on suspensory ligaments

    • -puts tension on lens causing it lengthen
    • *straighten out
  20. What occurs if we are trying to focus on distant objects
    -lens are flat

    -ciliary muscles are relaxed

    • -suspensory ligaments are pulled tightly
    • *emmetropia
    • **20 ft
  21. What process occurs when we are trying to focus on nearby object
    -ciliary muscles contract

    -release tension on ligaments

    -lens becomes more spherical

    *bending light rays more
  22. As you move towards something,
    Pupillary constriction occurs giving us greater depth of focus by light passing through lens center to make it easier to see
  23. When does convergence of pupils occur?
    When objects are too close to the nose our eyes rotate medially
  24. Retinal transduction of image
    -the inverted image must be translated from photons of light to AP in order for the CNS to understand it
  25. What is the pigmented retina?
    • Cells with melanin that reduce light scatter
    • *single layer
  26. What are the 2 receptor cells in sensory retina?
    Rods and cones
  27. When are rods activated/
    Dim light
  28. When are cones activated?
    • Bright light
    • *color
  29. which are the 2 relay cells in sensory retina?
    -bipolar cells

    -ganglion cells
  30. What are the 2 interneurons in sensory retina?

    -horizontal cells
  31. What are the relay cells going to do?
    Will carry AP from rods/cones toward CNS
  32. 2 functions of interneurons
    -synapse with different rods/cones

    -help provide integration in retina itself
  33. With what are rods/cones embedded in?
    Pigmented retina
  34. Where will transduction take place in rods/cones?
    Dendritic end
  35. What does the rods dendritic end contain?
    Unfolding of plasma membrane which forms discs.
  36. What is within the unfolding of plasma membrane that forms discs?
    A protein called rhodopsin
  37. What 2 components make up rhodopsin ?
    opsin and retinal
  38. What is rhodopsin important in?
    Initial step & transduction
  39. How does transduction process begin in rods?
    Bleaching, meaning when light hits rhodopsin it splits it into its 2 components (opsin and retinal)
  40. What is rhodopsin near?
    Na channels
  41. In the dark, the rod membrane is normally
  42. When light hits the rod membranes,
    NA channels close and hyperpolarization begins resulting in GP
  43. What does the dendritic end of cones contained?
    PM folded into membranous discs
  44. What do the membranous discs of cones contain?
  45. What are the 3 different iodopsin?


  46. What are the 2 components that make up iodopsin?

  47. What is the process of initiating transduction in cones called?
  48. What does the fovea centtralis contain/
    • Concentration of only cones
    • *it is located within macula lutea
  49. What does having cones/rods embedded in pigmented layer do?
    Allows for less scatter of light
  50. When we are focusing on something, what are we doing to fovea centrallis?
    Placing it directly to it
  51. What is the pathway in which the GP (then AP) has to travel to get realized?
    -Rod/cone to Bipolar cells to ganglion cells to optic disc to optic nerve to visual pathway in brain
  52. Which are the only cells to generate APs?
    Ganglion cells
  53. Visual diagram summary
    The medial of the Left and right eyes will pick up their own side ( left eye to left visual) but will be processed on the opposite side (left visual field to right visual cortex). The lateral points of eyes will process the middle area but will not cross and be processed on that same side (lateral left eye to center will not cross and be process on left visual cortex ).
  54. Which structure focuses and retracts?