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Photons to energize rhodopsin & trigger a nerve impulse

  1. Jun 12, 2015 #1
    I am wondering how many photons must be captured by a rhodopsin molecule to energize it, and also to trigger a nerve impulse to the brain or to deeper in the eyes neural system?
  2. jcsd
  3. Jun 13, 2015 #2


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  4. Jun 13, 2015 #3


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    It takes only one photon to isomerize the retinal in rhodopsin, and activate the rhodopsin molecule. Individual rod cells are capable of responding to an individual photon (http://journals.aps.org/rmp/abstract/10.1103/RevModPhys.70.1027), but as Pythagorean's link points out, some of the downstream neurons responsible for processing visual simuli may not be triggered by the signal from a single rod cell.
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