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Describe the molecular events that generate the "dark current" in photoreceptor cells; explain the impact of this cycle on the typical resting membrane potential, and how light leads to a hyperpolarization of the membrane.

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The dark current is caused by the inward flow of sodium ions into the outer segment of the photoreceptor cells. It is called the dark current because it occurs in the dark without any light stimulation. It keeps the photoreceptor cell depolarized in the dark. It occurs as long as cGMP ...

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