Resting Membrane Potential

The resting membrane potential is the electrical voltage across a neuron's membrane at rest, typically around -70 millivolts. This negative charge is essential for neuronal function because it provides the electrical foundation for generating signals and responding to stimuli. Without this potential difference, neurons cannot produce action potentials or communicate with other cells.

The sodium-potassium pump actively transports three sodium ions out of the cell and two potassium ions into the cell, using ATP energy. This unequal exchange creates and maintains ion concentration gradients across the membrane. The pump's continuous activity sustains the negative resting potential by keeping more positive ions outside the cell than inside.

The electrochemical gradient and channel proteins work together to establish resting potential by creating both chemical and electrical driving forces for ions. Potassium ions leak out through open channels down their concentration gradient, making the interior more negative. This ion movement continues until the electrical gradient balances the chemical gradient, stabilizing the resting membrane potential.

At rest, the neuronal membrane is more permeable to potassium than sodium because more potassium channels remain open while sodium channels are mostly closed. This selective permeability allows potassium to leak out of the cell, driving the membrane potential toward the potassium equilibrium potential. The differential permeability is crucial for maintaining the negative resting potential.

The resting membrane potential provides the starting point for action potential generation. When a neuron receives sufficient stimulation, the membrane potential depolarizes from its resting state of approximately -70 millivolts. This change triggers the opening of voltage-gated sodium channels, initiating the rapid depolarization phase of the action potential phases of stimulation.

If sodium-potassium pumps fail, ion gradients gradually dissipate and the resting membrane potential becomes less negative. Without active transport maintaining concentration differences, sodium accumulates inside the cell and potassium leaks out. Eventually, the membrane potential approaches zero, preventing neurons from generating action potentials and disrupting normal nervous system function.

Ion channels maintain resting potential stability through selective permeability and leak conductance. Open potassium channels allow continuous potassium efflux, while closed sodium channels prevent sodium influx. This balanced ion leakage, combined with active pumping, creates a steady-state equilibrium where the resting membrane potential remains stable at approximately -70 millivolts.