Homeostatic control mechanisms

Although exact values for physiological or biochemical variables show inter-individual variation, it is important for each value to be kept within a narrow range that is compatible with health. Such homeostasis must be achieved in spite of tendencies for changes to be produced by an individual’s environment and lifestyle. Tight and rapid control requires the existence of specific mechanisms: negative-feedback loops. These mechanisms form the basis of physiology, and this article deals with what they are, how they work, and the problems that can arise with them, and how these problems are solved in humans. The main function of such loops is to maintain a constant environment for the cells of the body, but they can also produce controlled change in a variable; for example, if a smooth movement (change of muscle length) is to be undertaken.