The Potential Difference Across a Cell

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  . --- The inner and outer surfaces of a cell membrane carry a negative and positive charge, respectively. Because of these charges, a potential difference of about 0.065 V exists across the membrane.

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  Once threshold is reached, sodium channels open wide and sodium ions flow into the cell. This influx of positive charges into the cell diminishes the electrical difference (voltage) across the membrane. This is called depolarization.

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