Final answer:
A negative membrane potential pushes positively charged sodium ions (Na+) out of the cell due to electrical force and is integral to maintaining the resting potential with the sodium-potassium pump.
Step-by-step explanation:
A negative membrane potential would exert an electrical force that pushes positively charged ions, specifically sodium ions (Na+), out of the cell. This occurs because a negative membrane potential means that the inside of the cell is negatively charged compared to its exterior, causing an attraction for cations and a repulsion for anions. Sodium ions, being positively charged, are repelled when the membrane potential is negative. This force works together with the chemical concentration gradient to form an electrochemical gradient.
The sodium-potassium pump also plays a crucial role in maintaining this negative interior by expelling more Na+ ions than it brings in K+ ions. For every cycle of the pump, three Na+ are pumped out for every two K+ ions that are pumped in, thus maintaining a net negative charge inside the cell. This activity is significant for the resting membrane potential, where the inside of the cell is maintained at around -70 mV.