Final answer:
The membrane potential is primarily influenced by the uneven distribution of sodium (Na+) and potassium (K+) ions across the cell membrane, maintained by selective permeability and the sodium-potassium pump.
Step-by-step explanation:
The membrane potential is mostly related to the uneven distribution of the positively charged ions sodium (Na+) and potassium (K+). When a cell is at rest, the concentration of Na+ is significantly higher outside the cell than inside, while K+ is more concentrated inside the cell. The resting membrane potential is largely established by the selective permeability of the cell's membrane to K+ and Na+ ions, and is maintained by the sodium-potassium pump which moves two K+ ions into the cell and three Na+ ions out of the cell at the cost of ATP, helping to sustain this ionic imbalance across the plasma membrane.