title: Biorhythms, system organization and bioactive compounds. I. Theoretical background.
abstract: Theoretical considerations are presented for the analysis of nonautonomous, nonlinear, and nonconservative systems. It was suggested that stability and the kind of oscillations are different expressions of the same thing, the response to external signals. A necessary condition of oscillatory systems is that the system consists of coupled units and that the system be influenced by external starting signals. Periodicities can only be observed when the energy dissipation of the system is compensated by maintaining signals. The internal description of biosystems is essentially structural, and the system behavior should be described in terms of system variables, their interrelationships, and the input-output relations in a single equation system.
mesh_terms: D005246:Feedback; D008962:Models, Theoretical; D010507:Periodicity; D010600:Pharmacology; D013598:Systems Theory; D013816:Thermodynamics