Rheostasis (biology)

Rheostasis refers to biochemical and physiological processes that serve the adaptive needs of an organism facing internal or external environmental challenges through graduated quantitative regulation, much like an electrician’s rheostat graduates current. As discussed in the article on allostasis, the human living system persists in the living state not only through mechanisms that regulate constancy of critical biological variables and processes &mdash; homeostasis &mdash; but also through mechanisms that change the set-point ranges of biological variables and processes so as to adapt to changing, sometimes seriously threatening circumstances. Biologists use the term ‘on/off switch’ when such re-setting occurs in a binary (‘on/off’) type manner, and ‘rheostat’ when the regulatory mechanism operates in a graduated, or quantitative, manner. Biologists see one example of rheostasis in the phenomenon of quantitative gene expression regulation by continuously variable ‘switches’ quantitatively coupled to enzyme activity.

This article will explore the many facets of the phenomenon of rheostasis, in particular in mammalian physiology in relation to homeostasis, allostasis, and systems biology.