Question

If you experimentally increase the concentration of na outside a cell while maintaining other ion concentrations as they were, what would happen to the cell's membrane potential?

O the membrane potential would become less negative.
O the membrane potential would be unaffected.
O the membrane potential would become more negative.
O the membrane potential would become positive.

Answer 1

Increasing extracellular Na+ concentration causes the cell's membrane potential to become less negative due to Na+ ions entering the cell, eventually leading to depolarization and potentially an action potential if the entry continues.

Step-by-step explanation:

If you experimentally increase the concentration of Na+ outside a cell while maintaining other ion concentrations, the cell's membrane potential would become less negative. This occurs because Na+ ions are more concentrated outside the cell, and upon opening Na+ channels, they will rush into the cell along the concentration gradient.

The influx of these positively charged ions will cause depolarization, meaning the membrane potential moves toward zero, and may even become positive if the entry of Na+ ions continues. In a resting state, the membrane potential is typically around -70 mV; thus, the increase in intracellular Na+ concentration will make the inside of the cell less negative relative to the outside.

Eventually, as the membrane potential reaches around +30 mV, other voltage-gated channels in the membrane may also open. This process is part of what occurs during the generation of a nerve signal or action potential, where the swift change in membrane potential is a critical factor in neuronal communication.