homeostasie

Homeostasis (homeostasie in French) is the property of a system to maintain internal stability. In biology, it refers to the regulation of many physiological variables within narrow limits, despite changes in the external environment.

The process relies on sensors that detect deviations, a control center that compares values to a set point, and effectors that adjust processes to restore balance. Negative feedback is the dominant mechanism; positive feedback reinforces a temporary change in certain contexts.

Common examples include body temperature, blood glucose, pH, and fluid balance. Hormonal and neural pathways coordinate responses: insulin and glucagon regulate glucose; antidiuretic hormone (ADH) and aldosterone regulate water and salt balance; thermoregulatory responses adjust heat production and loss.

Homeostasis is maintained by interactions among the nervous, endocrine, and sometimes immune systems. Circadian rhythms, acclimatization to high altitude or cold, and dehydration are examples of dynamic regulation.

Disruption can lead to disease and dysfunction, such as diabetes mellitus, electrolyte imbalance, fever, or dehydration. Treatments often aim to support or restore homeostatic control.

Historically, the concept was developed by Claude Bernard and popularized by Walter Cannon, who coined the term homeostasis. The idea underpins modern physiology and bioengineering.