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Sourav PanNovember 9, 2024

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

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

Sourav Pan
Sourav PanNovember 9, 2024

Answered

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

  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

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