Introduction to Homeostasis
Three common misconceptions regarding homeostasis are dispelled. First, the brain has the unique ability to mount an anticipatory defense against changes that could potentially push the body’s physiology out of homeostatic range. Such anticipation of needed adjustments is contrasted to the model of homeostasis as a servomechanism. Second, homeostasis depends on many neurons, not just those in the hypothalamus. Yet hypothalamic neurons play a special role in the integration of challenges and coordination of diverse effector reactions. Third, the idea that homeostasis is the purview of the autonomic nervous system is corrected. As exemplified by respiration and micturition, the brain employs skeletal muscle as well as autonomic targets in supporting visceral life. Finally, the allostatic perspective on the brain’s contribution to staying alive is contrasted with the standard homeostatic perspective and illustrated by examples.