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Vitamin A: Color Detection, Visual Cycle and Retinoic Acid Function

by Kevin Ahern, PhD
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    So the process that I’ve just described to you for the transmission of information from the eye cell to the brain is known pretty much for the rod cells. Less is known about how the process occurs in the cone cells but it is believed to happen in a pretty much the same way as in the rod cells. Now, as I said earlier, the cone cells have pigments that have varying sensitivity to different wavelengths of light. Cone cells need direct light and they need direct strong light in order to detect the colors that they detect. Cone cells as I said need more intense light. What would stimulate rod cell might not stimulate a cone cell. The detection process as I said, however, is pretty much the same. Now, the cone cells that have various maxima in the red region, for example, are more likely to fire if they get red light shined upon them whereas those that have maxima in the green, they get fire when the get green and those in the blue more likely when they get blue. The colors detected by the cone cells and by the brain, not by the sensitivity of any individual cells, but rather by a polling of groups of cells. So a group of blue cone cells in one cluster that all send a signal to the brain about blue color then tell the brain, “Yes, we really did get a blue color and that wasn’t an aberrant signal that we got. The brain then paints that image that we see as a result of these actions of these individual cells. Now, after vitamin A has been isomerized from the 11-cis to the trans form, it has to reconverted back to the 11-cis form. Now, I told you that...

    About the Lecture

    The lecture Vitamin A: Color Detection, Visual Cycle and Retinoic Acid Function by Kevin Ahern, PhD is from the course Vitamins. It contains the following chapters:

    • Vitamin A and Color Detection
    • Vitamin A and the Visual Cycle
    • Retinoic Acid Function

    Included Quiz Questions

    1. None of the answers are true.
    2. They are sensitive mostly to red light.
    3. They are about as sensitive to light as rod cells.
    4. They each cone cell directly gives a signal.
    5. All of the answers are true.
    1. ...requires ATP.
    2. ...requires conversion back to the all-trans state.
    3. ...occurs on opsin.
    4. All of the answers are true.
    5. None of the answers are true.

    Author of lecture Vitamin A: Color Detection, Visual Cycle and Retinoic Acid Function

     Kevin Ahern, PhD

    Kevin Ahern, PhD


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