During this step, the pump releases na+ into the extracellular fluid. na+ has now been transported from the cytoplasm to the extracellular fluid. which of the following best describes why na+ isn’t also transported in the opposite direction—from the extracellular fluid to the cytoplasm?

It is described the Na+/K+ pump and the Na+ does not return to the cell because the channels are closed.

Explanation:

During certain stimulus, as the nerve impulse, the Na+ channels are opened and the Na+ enter to the cytoplasm.

In order to recover the membrane potential and the electrochemical balance, the cell use the Na+/K+ pump, wich transport 3 Na+ outside the cell and enter 2 K+, using 1 ATP as energy.

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sorry if this did not , have a great day!