Final answer:
The resting membrane potential of a neuron, which is around -70 millivolts, is principally determined by the selective permeability of the membrane to potassium (K+) ions and the action of the sodium-potassium pump.
Step-by-step explanation:
The concentrations of ions inside and outside the neuron, especially potassium (K+) ions to which the resting membrane is selectively permeable, account for the resting membrane potential. The resting membrane potential is the electrical potential difference across the neuron's membrane at rest, which is approximately -70 millivolts. This negative charge inside the neuron is mainly due to the movement of potassium ions, which are at a higher concentration inside the neuron, through potassium channels out of the cell. Sodium ions (Na+), however, are maintained at high concentrations outside of the cell, and because the membrane at rest is less permeable to sodium, this contributes further to the negative potential inside. The sodium-potassium pump also plays a critical role in maintaining the resting membrane potential by pumping two K+ ions into the neuron while expelling three Na+ ions out for each molecule of ATP used.