What intracellular messenger is the primary regulator of adaptation of photoreceptors?
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As you know light triggers hyperpolarization of the plasma membrane in photoreceptive cells. Essentially light is absorbed by 11-cis-retinal. Retinal is covalently bound to a protein opsin to form rhodopsin. When light is absorbed by the 11-cis-retinal in rhodopsin, the retinal is isomerized to the all trans form. The all-trans form of retinal dissociates from the protein. The resulting protein, now activated, triggers the enzymatic cascade leading to hyperpolarization.
In the absence of light, sodium ion channels are open, allowing for passage of Na+ ions into the cell. This flow is called the "dark current" because it takes place in the absence of light. Once the Na+ ions flow ...
A solution that explains the primary regulator of both the physiological response and the adaptation of photoreceptors in the context of intracellular messengers.