Final answer:
The resting membrane potential is sustained by differences in sodium and potassium ion concentrations maintained by sodium-potassium pumps and ion channels, and is restored after depolarization even if ion concentrations are not initially balanced.
Step-by-step explanation:
The resting membrane potential of a neuron is typically around -70 millivolts, indicating a negative charge inside the cell relative to the outside. This electrical potential is created by the difference in ion concentrations of sodium (Na+) and potassium (K+) across the cell membrane. Sodium-potassium pumps maintain this membrane potential by expelling more Na+ ions from the cell than K+ ions taken in.
This pump operates by consuming ATP and expels three Na+ ions for every two K+ ions it imports. The neuron's membrane has more potassium leakage channels than sodium ones, allowing potassium to diffuse out more readily and maintain the negatively charged interior. Even after a nerve impulse alters the ion concentrations temporarily, the resting membrane potential is restored, although ion concentrations may not immediately return to their pre-impulse state due to ongoing cellular activities and ion channel permeabilities.