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SouravSeptember 23, 2024

There is a much greater K concentration inside the cell than outside. Why, then, is the resting membrane potential negative?

There is a much greater K concentration inside the cell than outside. Why, then, is the resting membrane potential negative?
Sourav
SouravSeptember 23, 2024

Answer

The resting membrane potential is negative despite the higher concentration of potassium ions (K⁺) inside the cell due to the selective permeability of the neuronal membrane. Here are the key reasons:

  1. Potassium Permeability: The neuronal membrane is more permeable to K⁺ than to other ions at rest. As K⁺ ions diffuse out of the cell down their concentration gradient, they leave behind negatively charged proteins and other anions inside the cell. This movement creates a net negative charge inside.
  2. Equilibrium Potential: The equilibrium potential for K⁺ (Eₖ) is around -80 mV, meaning that if the membrane were solely permeable to K⁺, the inside of the cell would be at this negative potential. The actual resting membrane potential is influenced by K⁺ but is typically around -65 mV, indicating a balance between the concentration gradient and the electrical gradient.
  3. Other Ion Influences: While K⁺ is the primary contributor to the resting membrane potential, sodium ions (Na⁺) and chloride ions (Cl⁻) also play roles. The lower permeability to Na⁺ at rest prevents it from significantly affecting the potential, allowing K⁺ to dominate.

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