A field and circuit thermodynamics for integrative physiology. I. Introduction to the general notions

In this first of three articles on a physical basis for integrative physiology, statistical mechanical concepts are developed into a field thermodynamics. The development begins by comparing the different ways change is viewed in biology compared to physics. The Hamiltonian field concept unites the two. The requirements of a thermostatic description are introduced; then those of nonequilibrium thermodynamics are added. Conditions suitable for continuum, near-equilibrium analysis of systems are given; then the role of physical forces in organization is discussed. The development returns to statistical mechanics, and introduces conservation principles and equations of change for ensembles of interacting units. A general notion of systems and thermodynamic engines is discussed next, and a narrative account of the explanatory scope of field thermodynamics is given. Its applications to living systems are the subject of the subsequent two articles of this series.