homeostasis
Sign in to saveIn biology, homeostasis (British also homoeostasis; ) is the state of steady internal physical and chemical conditions maintained by living organisms. This is the condition of optimal functioning for the organism and includes many variables, such as body temperature and fluid balance, being kept within certain pre-set limits (homeostatic range). Other variables include the pH of extracellular fluid, the concentrations of sodium, potassium, and calcium ions, as well as the blood sugar level, and these need to be regulated despite changes in the environment, diet, or level of activity. Each of t
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Homeostasis is the ability of living organisms to maintain stable internal physical and chemical conditions—like body temperature, fluid balance, and blood sugar—within a narrow range despite changes in their environment or activity level. This stable internal state is essential for an organism to function optimally and survive.
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33 sectionsContents
- Etymology
- History
- Overview
- Controls of variables
- Core temperature
- Blood glucose
- Iron levels
- Copper regulation
- Levels of blood gases
- Blood oxygen content
- Arterial blood pressure
- Calcium levels
- Sodium concentration
- Potassium concentration
- Fluid balance
- Blood pH
- Cerebrospinal fluid
- Neurotransmission
- Neuroendocrine system
- Gene regulation
- Energy balance
- Clinical significance
- Biosphere
- Predictive
- Other fields
- Risk
- Stress
- Technology
- Society and culture
- See also
- References
- Further reading
- External links
In biology, homeostasis (British also homoeostasis; ) is the state of steady internal physical and chemical conditions maintained by living organisms. This is the condition of optimal functioning for the organism and includes many variables, such as body temperature and fluid balance, being kept within certain pre-set limits (homeostatic range). Other variables include the pH of extracellular fluid, the concentrations of sodium, potassium, and calcium ions, as well as the blood sugar level, and these need to be regulated despite changes in the environment, diet, or level of activity. Each of these variables is controlled by one or more regulators or homeostatic mechanisms, which together maintain life.
Homeostasis is brought about by a natural resistance to change when already in its optimal conditions, and equilibrium is maintained by many regulatory mechanisms; it is thought to be the central motivation for all organic action. All homeostatic control mechanisms have at least three interdependent components for the variable being regulated: a receptor, a control center, and an effector. The receptor is the sensing component that monitors and responds to changes in the environment, either external or internal. Receptors include thermoreceptors and mechanoreceptors. Control centers include the respiratory center and the renin-angiotensin system. An effector is the target acted on, to bring about the change back to the normal state. At the cellular level, effectors include nuclear receptors that bring about changes in gene expression through up-regulation or down-regulation and act in negative feedback mechanisms. An example of this is in the control of bile acids in the liver.