The free energy of biomembrane and nerve excitation and the role of anesthetics

TL;DR

This paper explores how anesthetics influence nerve excitation by affecting the free energy difference between membrane phases, providing a theoretical framework that aligns with experimental data across various species.

Contribution

It introduces a model linking anesthetic effects on membrane phase transitions to nerve stimulation, supported by calculations and comparisons with experimental results.

Findings

Anesthetics lower the free energy barrier for nerve excitation.

The model accurately predicts stimulus-response curves across species.

Experimental data supports the role of membrane phase transitions in nerve excitation.

Abstract

In the electromechanical theory of nerve stimulation, the nerve impulse consists of a traveling region of solid membrane in a liquid environment. Therefore, the free energy necessary to stimulate a pulse is directly related to the free energy difference necessary to induce a phase transition in the nerve membrane. It is a function of temperature and pressure, and it is sensitively dependent on the presence of anesthetics which lower melting transitions. We investigate the free energy difference of solid and liquid membrane phases under the influence of anesthetics. We calculate stimulus-response curves of electromechanical pulses and compare them to measured stimulus-response profiles in lobster and earthworm axons. We also compare them to stimulus-response experiments on human median nerve and frog sciatic nerve published in the literature.