Chaos in Physiological Control Systems: Health or Disease?

During the nineties, the Rössler’s have reported in their famous book “Chaos in Physiology,” that “physiology is the mother of Chaos.” Moreover, several researchers have proved that Chaos is a generic characteristic of systems in physiology. In the context of disease, like for example growth of cancer cell populations, Chaos often refers to irregular and unpredictable patterns. In such cases, Chaos signatures can be used to prove the existence of some pathologies. However, for other physiological behaviors, Chaos is a form of order disguised as disorder and can be a signature of healthy physiological functions. This is for example the case of human brain behavior. As the boundary between health and disease is not always clear-cut in chaotic systems in physiology, some conditions may involve transitions between ordered and chaotic states. Understanding these transitions and identifying critical points can be crucial for predicting Healthy vs. pathological Chaos. Using recent advances in physiological Chaos and disease dynamics, this survey paper tries to answer the crucial question: when Chaos be a sign of health or disease?