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

Question

Sourav · Answer

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^{+}

-ATPase). This process establishes and maintains the necessary ionic gradients that allow neurons to be electrically excitable.

Mechanism of Sodium-Potassium Pump

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.
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.
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.

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