Negative feedback

Negative feedback feeds part of a system's output, inverted, into the system's input; generally with the result that fluctuations are attenuated. Many real-world systems have one or several points around which the system gravitates. In response to a perturbation, a negative feedback system with such point(s) will tend to re-establish equilibrium.

In many physical and biological systems, qualitatively different influences can oppose each other. For example, in biochemistry, one set of chemicals drives the system in a given direction, whereas another set of chemicals drives it in an opposing direction. If one, or both of these opposing influences are non-linear, an equilibrium point(s) results.

In Biology, this process (generally biochemical) is often referred to as Homeostasis.

Examples
Some biological systems exhibit negative feedback such as the baroreflex in blood pressure regulation and erythropoiesis. Many biological process (e.g., in the human anatomy) use negative feedback. Examples of this are numerous, from the regulating of body temperature, to the regulating of blood glucose levels. The disruption of negative feedback can lead to undesirable results: in the case of blood glucose levels, if negative feedback fails, the glucose levels in the blood may begin to rise dramatically, thus resulting in diabetes.