How do neurons pump sodium and potassium ions across their membranes to generate a resting potential?

Neurons generate a resting potential through the active transport of sodium (Na++) and potassium (K++) ions across their membranes, primarily facilitated by the sodium-potassium pump (Na+/K++/K+-ATPase). This process establishes and maintains the necessary ionic gradients that allow neurons to be electrically excitable.

Mechanism of Sodium-Potassium Pump

1. Active Transport:
   The sodium-potassium pump is an active transporter that uses energy from ATP hydrolysis to move ions against their concentration gradients. For every cycle of the pump:
   • 3 sodium ions are transported out of the neuron.
   • 2 potassium ions are transported into the neuron.

   This unequal exchange results in a net loss of positive charge from the cell, contributing to a more negative internal environment compared to the outside.

2. Establishing Ionic Gradients:
   The pump maintains high concentrations of Na++ outside the neuron and K++ inside. At rest, neurons are much more permeable to K++ than to Na++. As K++ ions leak out through potassium leakage channels, the internal charge becomes more negative, leading to a typical resting membrane potential of approximately -70 mV.
3. Membrane Potential:
   The resting potential is primarily determined by:
   • The concentration gradients of Na++ and K++.
   • The selective permeability of the neuronal membrane to these ions. Since the membrane is more permeable to K++, it allows more K++ to exit than Na++ to enter, reinforcing the negative charge inside the neuron.

Importance of Resting Potential

The resting potential is crucial for several reasons:

• Electrical Excitability: It creates a polarized state that enables neurons to respond quickly to stimuli by generating action potentials when depolarization occurs.
• Signal Transmission: The maintenance of this potential ensures that neurons can efficiently transmit signals along their axons and communicate with other neurons or muscles