Question

the movement of sodium ions from a region of lower concentration inside a cell toward a region of higher concentration outside the cell is accomplished by _________.

Explanation:

The movement of substances from a lower concentration to a higher concentration (against the concentration gradient) requires energy and is done by active transport. Sodium ions moving from inside the cell (lower concentration) to outside (higher concentration) is an example of active transport, often via the sodium - potassium pump which uses ATP for energy.

Answer:

active transport (or sodium - potassium pump, as the sodium - potassium pump is a type of active transport that moves sodium ions out of the cell against their concentration gradient)