Homeostasis is the subject, and under review here is an enormous piece of work, published by Frontiers in Physiology by George E. Billman. He credits pioneers Claude Bernard and Walter Cannon with spreading the notion that “the health and vitality of the organism can be said to be the end result of homeostatic regulation,” and also the concept that a physician’s role is to “clear the path so that nature could take its course.”
[H]omeostatic regulation is not merely the product of a single negative feedback cycle but reflects the complex interaction of multiple feedback systems that can be modified by higher control centers. This hierarchical control and feedback redundancy results in a finer level of control and a greater flexibility that enables the organism to adapt to changing environmental conditions.
Regulation is an interesting word, because rather than rolling up on a problem with heavy artillery, it suggests more of an incremental approach. One regulates a thermostat, or a carburetor. In order for this to be effective, the parts and the system have to work together as a complex and multifactorial community.
Homeostasis, then, is the tendency of a system to maintain an internal stability as the result of the coordinated response of its parts to any situation or stimulus that disturbs normal conditions or function.
As previously noted, Cannon specified that homeostasis does not mean immobility, but “a condition which may vary, but is relatively constant.” Various things are going on at three different levels:
— physiochemical processes, the organ and tissue functions, the component parts upon which homeostasis acts.
— autonomous (self) regulation… [C]hanges in a given variable are sensed and adjustments of the first level processes are initiated…
— central command and control centers (central nervous system) that process the information transmitted from the second level and integrates it with information from other sensory inputs to coordinate the physiological and behavioral response to changing environmental conditions.
The higher centers can intervene either consciously or unconsciously, but only — and this is vital — if the first and second levels are working properly. For good or ill, there are also higher levels of control outside the organism. The body can signal urgently that it needs water, and the conscious mind may concur, but the reality of the situation, e.g. being lost in a desert, will win.
Another outside control mechanism might be a medical care system that cannot or will not take the appropriate measures. In his Summary, Billman reaffirms that disease is caused by disruption of the homeostatic mechanisms, and “effective therapy must be directed toward re-establishing these homeostatic conditions, working with rather than against nature.”
J. S. Turner in 2017 suggested “dynamic disequilibrium” as a fitting description of homeostasis, and went so far as to say “homeostasis is life’s fundamental property, what distinguishes it from non-life. In short, homeostasis is life.”
Your responses and feedback are welcome!
Source: “Homeostasis: The Underappreciated and Far Too Often Ignored Central Organizing Principle of Physiology,” Frontiersin.org/articles, 03/10/20
Image by Pat Hartman