Biology Forum Human Biology Black and white

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    • #3172
      hoiki426
      Participant

      1.)When in bright condition
      The black and white colour is detected by cone or rod?

      My book said"Rod is for black and white vision"

      but…..

      I have done a HKCEE mc(30/99)
      It said:

      "When you are reading through a page , only a few words can be seen clearly each time.This is because

      only a few words can be focused onto the yellow spot each time."

      There is just cone on the yellow spot and the words on the book is usually black in colour…………………………………..

      The black and white colour is detected by cone or rod?

      2.) What kind of eye disease will be caused if our lens is not elastic?

      Th for answering me so many questions~><

    • #36921
      Dr.Stein
      Participant

      RODS are more sensitive to light than are cones, and rods are particularly important for night vision. The outer segment of rods is an elongate cylinder of cytoplasm. Within this is column of discs which are flattened membrane bubbles whose contents are technically extracellular. These hollow wafers are produced continuously from the basal portion of the outer segment, forming as projections of cytoplasm that serially fuse to form the discs. These mature discs are not connected at all to the plasma membrane.

      CONES operate at higher light intensities and are the main receptor of "daylight" vision, since rods saturate at very low light levels and essentially cease to function. All color distinction is due to cone function, based on the existance of three subtypes of cones sensitive to three distinct light wavelengths. Rods respond only to one narrow band of light frequency, and rod-only retinas are entirely colorblind. Cones have a much shorter outer segment than do rods, and the developing membranous processes that in rods fuse into the disc series–remains unfused in the rods. This gives these cells the appearance of bearing a kind of comb on their outer segment, but keep in mind that in 3-D, that is really a series of plates joined at the ciliary end.

    • #37203
      hoiki426
      Participant

      So…
      I still have one question.

      What kind of eye disease will be caused if our lens is not elastic?

    • #37217
      MrMistery
      Participant

      This occurs in old people. As you get older, it is harder and harder to see things close to you. Punctum proxim moves from 7 to 80 centimeters away from the eye. The condition is called presbyopia

    • #37238
      Dr.Stein
      Participant

      Here it is the figure of presbyopia 🙂

    • #37299
      MrMistery
      Participant

      At the rate you are posting pictures and i am saving them, i will have your entire collection by next year.

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