Final answer:
If a membrane were equally permeable to K+ and Na+, and not permeable to any other ions, the resting membrane potential would still be -70 mV.
Step-by-step explanation:
A neuron at rest is negatively charged: the inside of a cell is approximately 70 millivolts more negative than the outside (-70 mV). This voltage is called the resting membrane potential; it is caused by differences in the concentrations of ions inside and outside the cell and the selective permeability created by ion channels.
If the membrane were equally permeable to K+ and Na+, and not permeable to any other ions, the resting membrane potential would still be -70 mV. This is because K+ ions would move out of the cell through potassium channels, creating a net negative charge inside the cell.
The actions of the sodium-potassium pump help maintain the resting potential by bringing in two K+ ions for every three Na+ ions removed. This pump accounts for the differences in ion concentrations inside and outside the cell.