During rod phototransduction, what is the immediate effect on membrane potential when Na+ channels close?

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Multiple Choice

During rod phototransduction, what is the immediate effect on membrane potential when Na+ channels close?

Explanation:
Closing the Na+ channels stops the inward current that kept the rod depolarized in darkness. With that inward breeze gone, the outward K+ current dominates, pulling the membrane potential to a more negative value. In other words, the rod rapidly hyperpolarizes. This hyperpolarization reduces neurotransmitter release at the synapse, signalling light detection to downstream neurons.

Closing the Na+ channels stops the inward current that kept the rod depolarized in darkness. With that inward breeze gone, the outward K+ current dominates, pulling the membrane potential to a more negative value. In other words, the rod rapidly hyperpolarizes. This hyperpolarization reduces neurotransmitter release at the synapse, signalling light detection to downstream neurons.

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