Heat of nervous conduction: A thermodynamic framework

Area of Science:

• Neuroscience
• Biophysics
• Physical Chemistry

Background:

• Nervous conduction is associated with a thermal signature.
• Heat production and absorption during action potentials involve physicochemical processes at the cell membrane.
• The existing Condenser Theory offers a basic analogy but lacks quantitative explanation for the observed heat magnitude.

Purpose of the Study:

• To revisit and quantitatively analyze the Condenser Theory using a detailed electrostatic model of the cell membrane.
• To derive expressions for energy and entropy changes during action potential depolarization.
• To investigate the impact of surface charge density on heat production and absorption.

Main Methods:

• Development of a detailed electrostatic model for the cell membrane.
• Derivation of free energy and entropy changes during membrane depolarization.
• Analysis of the influence of surface charge density on electrostatic energy changes.
• Simulation using a typical action potential and specific surface charge bias.

Main Results:

• Expressions for heat production and absorption were derived from electrostatic energy and entropy changes.
• Surface charge density significantly impacts the energy dynamics across the membrane.
• A specific surface charge bias (0.05 C/m² negative on the internal side) yields predicted heat values consistent with experimental observations.

Conclusions:

• The release of electrostatic energy from the cell membrane is the primary mechanism for heat production and absorption during nervous conduction.
• The refined Condenser Theory, incorporating surface charge effects, provides a quantitative explanation for the thermal signature of action potentials.
• This work bridges the gap between electrostatic principles and the biophysical phenomena of neuronal signaling.