AJP - Regulatory, Integrative and Comparative Physiology, Vol 238, Issue 5 413-R420, Copyright © 1980 by American Physiological Society
Irreversible thermodynamics of an isometric twitch, time-dependent general formulation
A. H. Moreno, H. H. Chiu, J. A. Steen and R. V. Reddy
We used the phenomenological laws of irreversible thermodynamics, to derive
a system of coupled differential equations describing the time course of
the mechanochemical coupling underlying an isometric twitch. Our general
description is concerned only with the fundamental process of energy
transduction taking place within an idealized unit element of muscle and
does not include the description of associated processes such as the
excitation-contraction coupling and the mechanical or external coupling
that, in bulk muscle, lead to or mediate the fundamental process. The
values of the initial conditions and of four parameters are required to
solve for the time course of the process. Two of the parameters have a
clear physical interpretation and, for the specific case of muscular
contraction involving hydrolysis of ATP, their values can be readily
estimated from available experimental data. The interpretation of the two
other parameters is more speculative, but, from their strong
interdependence with the other parameters, their values can be also
approximated. Solution of the coupled differential equations yields results
consistent with the typical experimental time course of an isometric
twitch.
