Intro to Homeostasis

Homeostasis can be defined as the maintenance of physiological conditions required to maintain the life of the organism.

Every living thing and every organ is by necessity subject to homeostatic regulation. We can not examine every instance of homeostatic control but will focus on how electrolytes and temperature are regulated.

Footnote: Both positive and negative feedback occurs when the result of some process returns to affect the subsequent course of that process.

Positive feedback generally results in a shift away form equilibrium - a cascade of events which leads to a dramatic change in a physiological state. Such self reinforcing cycles help establish the uterine lining and the enlargement of limbs during development

Negative feedback is the classic mechanism which maintains the status quo. A response to a stimulus leads to a reaction which ultimately reduces the response. Even if the stimulus remains, the response becomes less and less exaggerated. See the diagram below.



Negative feedback loops are inherently stabilizing and eventually establish equilibrium.

Negative feedback is used to control enzyme activity.

Modified July 10, 2005