Chronostasis: The Timing of Physiological Systems

Abstract

Even though the biological relevance of circadian rhythmicity has been recognized since the middle of the past century, the majority of the medical community has remained unaware of the circadian rhythms or their relevance during most of this time, perhaps because of their apparent opposition to homeostasis. It was not until the 1980s that circadian rhythms begun to be noticed among the physicians, but even now, 30 years later, circadian rhythms are still not an integral part of medical physiology. The cause of the neglect and even rejection of the relevance of circadian biology to human health, from most medical practitioners until the last quarter of the twentieth century, may have involved among other factors: (1) the heuristic power of homeostasis as a general physiological process to understand health, and its unbalance as a major cause of disease; (2) the fact that disruption of circadian rhythmicity was not ostensibly associated at the time with any pathological entity; and, last but not least, (3) the technical problems associated with collecting relevant physiological data for a long time period before the age of electronic devices and massive digital information processing.

This chapter presents a perspective for integrating circadian rhythmicity and its mechanisms with medical physiology. We start by a brief review of the concepts of homeostasis and rheostasis in physiology, then introduce the concept of chronostasis as the mechanism to timing physiological processes. Finally, we provide the main implications of the concept of chronostasis in human health and disease, in light of the recent advances in molecular genetics related to the so-called clock genes.