Conventional framing
Physiology is traditionally understood as the study of how biological systems function—how organs, tissues, and cells operate to maintain life, often described in mechanistic or systems terms.
APS reframing
In APS, physiology is the present-tense organisation of activity through which a living system sustains its own viability. It is not simply the functioning of parts, but the coordinated regulation of constraint-closed processes that maintain coherence across scales.
Physiology expresses viability-oriented activity in real time. It integrates molecular, cellular, and organismal processes into a continuously modulated system that responds to perturbation, maintains stability, and enables persistence.
Key Point
Physiology is the present-tense enactment of persistence—the coordinated activity through which viability-oriented organisation is sustained in real time.