-70 mV
Resting Membrane Potential
EXTRACELLULAR (OUT)
[Na⁺]145 mM
[K⁺]5 mM
[Cl⁻]110 mM
INTRACELLULAR (IN)
[Na⁺]15 mM
[K⁺]150 mM
[Cl⁻]10 mM
Goldman-Hodgkin-Katz (GHK) Eq:
■ Resting State:
The membrane is highly permeable to Potassium (K⁺ leak channels are open), pinning the resting potential near the K⁺ Nernst equilibrium (-90mV).
■ Action Potential:
When Voltage-Gated Na⁺ channels open dramatically, Permeability (P_Na) spikes, washing out P_K, and driving the voltage towards the Na⁺ Nernst eq (+60mV).
Vm = (RT/F) * ln(P_K[K]o + P_Na[Na]o + P_Cl[Cl]i) / (P_K[K]i + P_Na[Na]i + P_Cl[Cl]o)■ Resting State:
The membrane is highly permeable to Potassium (K⁺ leak channels are open), pinning the resting potential near the K⁺ Nernst equilibrium (-90mV).
■ Action Potential:
When Voltage-Gated Na⁺ channels open dramatically, Permeability (P_Na) spikes, washing out P_K, and driving the voltage towards the Na⁺ Nernst eq (+60mV).