Homeostasis ( ancient Greek ὁμοιοστάσις homoiostásis , German 'equality' ) is a state of equilibrium and describes a state of equilibrium of an open dynamic system that is maintained by an internal regulating process. It is therefore a special case of the self-regulation of systems. The term is used in numerous disciplines such as physics , chemistry , biology , ecology , economics , sociology , psychology , medicine or law . A system in homeostasis is a homeostat .
Biology knows many states of equilibrium, which are maintained by special homeostatic processes. The equilibrium can be maintained within a cell, an organ or via an organism. The property to be obtained can be anatomical, chemical, physical or mathematical (number of cells). In physiology , the concept of homeostasis is defined as the maintenance of an internal milieu (target state) that comes about through regulation . An example of this is the homeostasis of the brain , which is maintained by the blood-brain barrier .
- Volume and osmoregulation
- Calcium and phosphate balance
- Acid-base balance
- Breathing drive for homeostasis of the partial pressures of oxygen and CO 2 and for the respiratory compensation of acid-base disorders
- Blood pressure regulation
- Iron Stock Homeostasis
- Regulation of blood sugar levels
- Regulation of the energy balance, see energy expenditure , energy balance (nutrition) , obesity , glucagon , insulin , leptin , thermogenin , adipocytes , starvation metabolism ; Disorders: metabolic syndrome , insulin resistance , leptin resistance
- Reflexes to secure the posture against gravity or external disturbances
- Sleep and homeostatic pressure (sleep pressure). The need for sleep increases while you are awake and decreases again during sleep. Adenosine plays an important role here.
In the case of social systems, Niklas Luhmann , Francisco Varela and Humberto R. Maturana have advocated replacing the term homeostasis with the term homeodynamics , since stasis would denote a standstill and thus the death of a (self-regulating) system.
Clinical homeostasis is used in connection with hormone production.
- Steady state
- Control engineering
- Regulation (nature and technology)
- Chemical equilibrium
- Jörg Martin , Jörg Hardy, Stephan Cartier (eds.): The world in flux. Case studies on the homeostasis model. Franz Steiner, Stuttgart 2008, ISBN 978-3-515-08980-7 .
- A. Rodenbeck, Bundesgesundheitsbl 2011 · 54: 1270-1275
- When all signals are on sleep , Deutschlandfunk
- Hans Joachim Flechtner : Basic concepts of cybernetics. Hirzel, 1972.
- Cornelius Borck: The wisdom of homeostasis and the freedom of the body. Walter B. Cannon's integrated theory of the organism. In: Zeithistorische Forschungen / Studies in Contemporary History. Volume 11, No. 3, 2014, pp. 472-477, doi: 10.14765 / zzf.dok-1469 .
- QuickGO: GO: 0042592 homeostatic process
- Harrisons: Internal Medicine. 18th edition, p. 3113.