Homeostasis (from Greek: ὅμος, homos, "equal"; and ιστημι, histemi, "to stand" lit. "to stand equally"; coined by Walter Bradford Cannon) is the property of either an open system or a closed system, especially a living organism, that regulates its internal environment so as to maintain a stable, constant condition. Multiple dynamic equilibrium adjustments and regulation mechanisms make homeostasis possible. The concept was created by Claude Bernard, often considered as the father of physiology, and published in 1865. Walter Bradford Cannon (Prairie du Chien, Wisconsin, October 19, 1871 – Lincoln, Massachusetts, October 19, 1945) was an American physiologist. ... This article is about systems theory. ... In thermodynamics, a closed system, as contrasted with an isolated system, can exchange heat and work, but not matter, with its surroundings. ... Domains and Kingdoms Nanobes Acytota Cytota Bacteria Neomura Archaea Eukaryota Bikonta Apusozoa Rhizaria Excavata Archaeplastida Rhodophyta Glaucophyta Plantae Heterokontophyta Haptophyta Cryptophyta Alveolata Unikonta Amoebozoa Opisthokonta Choanozoa Fungi Animalia An ericoid mycorrhizal fungus Life on Earth redirects here. ... A dynamic equilibrium occurs when two reversible processes occur at the same rate. ... For the 17th Century Roman Catholic priest who popularized the Memorare, see Father Claude Bernard. ... This article or section does not cite any references or sources. ...

Biological homeostasis

Further information: Human homeostasis

With regard to any given life system parameter, an organism may be a conformer or a regulator. Regulators try to maintain the parameter at a constant level over possibly wide ambient environmental variations. On the other hand, conformers allow the environment to determine the parameter. For instance, endothermic animals maintain a constant body temperature, while ectothermic animals exhibit wide body temperature variation. Examples of endothermic animals include mammals and birds, examples of ectothermic animals include reptiles and some sea animals. The factual accuracy of this article is disputed. ... For other uses, see Animal (disambiguation). ... Cold-blooded organisms, more technically known as poikilothermic, are animals that have no internal metabolic mechanism for regulating their body temperatures. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... For other meanings of bird, see bird (disambiguation). ... Orders  Crocodilia - Crocodilians scary crocodiles. ...

This is not to say that conformers don't have behavioural adaptations allowing them to exert some control over a given parameter. For instance, reptiles often rest on sun-heated rocks in the morning to raise their body temperature. Vice versa, regulators are usually responsive to external circumstances: if the same sun-baked boulder happens to host a ground squirrel, its metabolism will adjust to the lesser need for internal heat production. Behavior or behaviour refers to the actions or reactions of an object or organism, usually in relation to the environment. ... The eye is an adaptation. ... Reptilia redirects here. ... Sol redirects here. ... This article is about the geological substance. ...

Thermal image of a cold-blooded tarantula on a warm-blooded human hand

An advantage of homeostatic regulation is that it allows an organism to function effectively in a broad range of environmental conditions. For example, ectotherms tend to become sluggish at low temperatures, whereas a co-located endotherm may be fully active. That thermal stability comes at a price since an automatic regulation system requires additional energy. One reason snakes may eat only once a week is that they use much less energy to maintain homeostasis. Image File history File links Wiki_tarantula. ... Image File history File links Wiki_tarantula. ... For other uses, see Tarantula (disambiguation). ... For other uses, see Snake (disambiguation). ...

Most homeostatic regulation is controlled by the release of hormones into the bloodstream. However other regulatory processes rely on simple diffusion to maintain a balance.

Homeostatic regulation extends far beyond the control of temperature. All animals also regulate their blood glucose, as well as the concentration of their blood. Mammals regulate their blood glucose with insulin and glucagon. These hormones are released by the pancreas. If the pancreas is for any reason unable to produce enough of these two hormones diabetes results. The kidneys are used to remove excess water and ions from the blood. These are then expelled as urine. The kidneys perform a vital role in homeostatic regulation in mammals, removing excess water, salt, and urea from the blood. These are the body's main waste products. In medicine, blood sugar is glucose in the blood. ... Not to be confused with inulin. ... Glucagon ball and stick model A microscopic image stained for glucagon. ... This article is about the disease that features high blood sugar. ... Kidneys viewed from behind with spine removed The kidneys are bean-shaped excretory organs in vertebrates. ... This article is about the urine of animals generally. ...

Sleep timing depends upon a balance between homeostatic sleep propensity, the need for sleep as a function of the amount of time elapsed since the last adequate sleep episode, and circadian rhythms which determine the ideal timing of a correctly structured and restorative sleep episode.^[1] A circadian rhythm is an approximate daily periodicity, a roughly-24-hour cycle in the biochemical, physiological or behavioral processes of living beings, including plants, animals, fungi and cyanobacteria. ...

Control Mechanisms

All homeostatic control mechanisms have at least three interdependent components for the variable being regulated: The receptor is the sensing component that monitors and responds to changes in the environment. When the receptor senses a stimulus, it sends information to a control center, the component that sets the range at which a variable is maintained. The control center determines an appropriate response to the stimulus. The result of that response feeds to the effector, either enhancing it with positive feedback or depressing it with negative feedback ^[2]

Positive Feedback Mechanisms

Positive feedback is a mechanism by which an output is enhanced, such as protein levels. However, in order to avoid any fluctuation in the protein level, the mechanism is inhibited stochastically (I), therefore when the concentration of the activated protein (A) is past the threshold ([I]), the loop mechanism is activated and the concetration of A increases exponentially if d[A]=k [A]

Positive feedback mechanisms are designed to accelerate or enhance the output created by a stimulus that has already been activated. Positive feedback is a mechanism by which an output is enhanced. ...

Unlike negative feedback mechanisms that initiate to maintain or regulate physiological functions within a set and narrow range, the positive feedback mechanisms are designed to push levels out of normal ranges. To achieve this purpose, a series of events initiates a cascading process that builds to increase the effect of the stimulus. This process can be beneficial but is rarely used by the body due to risks of the acceleration becoming uncontrollable.

One positive feedback example event in the body is blood platelet accumulation, which, in turn, causes blood clotting in response to a break or tear in the lining of blood vessels. Another example is the release of oxytocin to intensify the contractions that take place during childbirth.^[2] A 250 ml bag of newly collected platelets. ... Coagulation is the thickening or congealing of any liquid into solid clots. ... Oxytocin (Greek: quick birth) is a mammalian hormone that also acts as a neurotransmitter in the brain. ...

Positive feedback can also be harmful. One particular example is when a fever causes a positive feedback within homeostasis that pushes the temperature continually higher. Body temperature can reach extremes of 45°C (113°F), at which cellular proteins denature, causing the active site in proteins to change, thus causing metabolism to stop, resulting in death. An analogue medical thermometer showing the temperature of 38. ...

Homeostatic Imbalance

Much disease results from disturbance of homeostasis, a condition known as homeostatic imbalance. As it ages, every organism will lose efficiency in its control systems. The inefficiencies gradually result in an unstable internal environment that increases the risk for illness. In addition, homeostatic imbalance is also responsible for the physical changes associated with aging. Even more serious than illness and other characteristics of aging, is death. Heart failure has been seen where nominal negative feedback mechanisms become overwhelmed, and destructive positive feedback mechanisms then take over.^[2]

Diseases that result from a homeostatic imbalance include diabetes, dehydration, hypoglycemia, hyperglycemia, gout, and any disease caused by a toxin present in the bloodstream. All of these conditions result from the presence of an increased amount of a particular substance. In ideal circumstances, homeostatic control mechanisms should prevent this imbalance from occurring, but, in some people, the mechanisms do not work efficiently enough or the quantity of the substance exceeds the levels at which it can be managed. In these cases, medical intervention is necessary to restore the imbalance, or permanent damage to the organs may result. This article is about the disease that features high blood sugar. ... Dehydration (hypohydration) is the removal of water (hydro in ancient Greek) from an object. ... Hypoglycemia (hypoglycaemia in British English) is a medical term referring to a pathologic state produced by a lower than normal level of glucose (sugar) in the blood. ... Hyperglycemia, hyperglycaemia, or high blood sugar is a condition in which an excessive amount of glucose circulates in the blood plasma. ...

Varieties of homeostasis

The Dynamic Energy Budget theory for metabolic organisation delineates structure and (one or more) reserves in an organism. Its formulation is based on three forms of homeostasis: Dynamic Energy Budget (DEB) theory aims to identify simple quantitative rules for the organization of metabolism of individual organisms that can be understood from basic first principles, The word Dynamic refers to the life cycle perspective of the theory, where the budget changes dynamically over time. ...

• Strong homeostasis, wherein structure and reserve do not change in composition. Since the amount of reserve and structure can vary, this allows a particular change in the composition of the whole body (as explained by the Dynamic Energy Budget theory).
• Weak homeostasis, wherein the ratio of the amounts of reserve and structure becomes constant as long as food availability is constant, even when the organism grows. This means that the whole body composition is constant during growth in constant environments.
• Structural homeostasis, wherein the sub-individual structures grow in harmony with the whole individual; the relative proportions of the individuals remain constant.

Dynamic Energy Budget (DEB) theory aims to identify simple quantitative rules for the organization of metabolism of individual organisms that can be understood from basic first principles, The word Dynamic refers to the life cycle perspective of the theory, where the budget changes dynamically over time. ...

Ecological homeostasis

Ecological homeostasis is found in a climax community of maximum permitted biodiversity, given the prevailing ecological conditions. The term climax community, also described as a climatic climax community, is a largely obsolete ecological term for a biological community of plants and animals which, through the process of ecological succession - the development of vegetation in an area over time - has reached a steady state. ... Rainforests are among the most biodiverse ecosystems on earth Biodiversity is the variation of life forms within a given ecosystem, biome or for the entire Earth. ...

An example of a disturbed ecosystems or sub-climax biological communities was the island of Krakatoa after its major eruption in 1883: the established stable homeostasis of the previous forest climax ecosystem was destroyed and all life eliminated from the island. In the years after the eruption, Krakatoa went through a sequence of ecological changes in which successive groups of new plant or animal species followed one another, leading to increasing biodiversity and eventually culminating in a re-established climax community. This ecological succession on Krakatoa occurred in a number of stages; a sere is defined as "a stage in a sequence of events by which succession occurs". The complete chain of seres leading to a climax is called a prisere. In the case of Krakatoa, the island reached its climax community, with eight hundred different recorded species, in 1983, one hundred years after the eruption that cleared all life off the island. Evidence confirms that this number has been homeostatic for some time, with the introduction of new species rapidly leading to elimination of old ones. A coral reef near the Hawaiian islands is an example of a complex marine ecosystem. ... A biocoenosis (alternatively, biocoenose or biocenose), termed by Karl Möbius in 1877, describes all the interacting organisms living together in a specific habitat (or biotope). ... This article is about the volcano. ... This article is about a community of trees. ... Secondary succession: trees are colonizing uncultivated fields and meadows. ... This article or section does not cite its references or sources. ... It has been suggested that this article or section be merged with Seral community. ...

The evidence of Krakatoa, and other disturbed or virgin ecosystems, shows that the initial colonization by pioneer or R strategy species occurs through positive feedback reproduction strategies, wherein species are weeds, producing huge numbers of possible offspring, but investing little in the success of any one. Rapid boom and bust plague or pest cycles are observed with such species. As an ecosystem starts to approach climax, these species get replaced by more sophisticated climax species, which, through negative feedback, adapt themselves to specific environmental conditions. These species, closely controlled by carrying capacity, follow K strategies, wherein species produce fewer numbers of potential offspring, but invest more heavily in securing the reproductive success of each one to the micro-environmental conditions of its specific ecological niche. In ecology, r/K selection theory relates to the selection of traits (in organisms) that allow success in particular environments. ... Yellow starthistle, a thistle native to southern Europe and the Middle East that is an invasive weed in parts of North America. ... In economics, the term boom and bust refers to the movement of an economy through economic cycles. ... Carpet beetle larvae damaging a specimen of Sceliphron destillatorius in an entomological collection A pest is an organism which has characteristics that are regarded as injurious or unwanted. ... The supportable population of an organism, given the food, habitat, water and other necessities available within an ecosystem is known as the ecosystems carrying capacity for that organism. ... Two lichens on a rock, in two different ecological niches In ecology, a niche (pronounced nich, neesh or nish)[1] is a term describing the relational position of a species or population in its ecosystem[1]. A shorthand definition is that a niche is how an organism makes a living. ...

It begins with a pioneer community and ends with a climax community. This climax community occurs when the ultimate vegetation has achieved equilibrium with the local environment.

Such ecosystems form nested communities or heterarchies, in which homeostasis at one level contributes to homeostatic processes at another holonic level. For example, the loss of leaves on a mature rainforest tree creates space for new growth, and contributes to the plant litter and soil humus build-up upon which such growth depends. Of equal importance, a mature rainforest tree reduces the sunlight falling on the forest floor and helps prevent invasion by other species. But trees too fall to the forest floor, and a healthy forest glade is dependent upon a constant rate of forest regrowth, produced by the fall of logs, and the recycling of forest nutrients through the respiration of termites and other insect, fungal, and bacterial decomposers. In a similar manner, such forest glades contribute ecological services, such as the regulation of microclimates or of the hydrological cycle for an ecosystem, and a number of different ecosystems act together to maintain homeostasis, perhaps of a number of river catchments within a bioregion. A diversity of bioregions, in like manner, makes up a stable homeostatic biological region or biome. A holon (Greek: holos, whole) is something that is simultaneously a whole and a part. ... Blanket of reddish-brown ponderosa pine needles covering the ground. ... Loess field in Germany Surface-water-gley developed in glacial till, Northern Ireland For other uses, see Soil (disambiguation). ... -1... The rocky area in this picture is an example of a glade A glade is an open area within a woodland. ... Orders Subclass Apterygota Archaeognatha (bristletails) Thysanura (silverfish) Subclass Pterygota Infraclass Paleoptera (Probably paraphyletic) Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Infraclass Neoptera Superorder Exopterygota Grylloblattodea (ice-crawlers) Mantophasmatodea (gladiators) Plecoptera (stoneflies) Embioptera (webspinners) Zoraptera (angel insects) Dermaptera (earwigs) Orthoptera (grasshoppers, etc) Phasmatodea (stick insects) Blattodea (cockroaches) Isoptera (termites) Mantodea (mantids) Psocoptera... Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... Microclimate on rock located in intertidal zone on rock at Sunrise-on Sea Tree ferns thrive in a protected dell at the Lost Gardens of Heligan, in Cornwall, England, latitude 50° 15N A microclimate is a local atmospheric zone where the climate differs from the surrounding area. ... The water cycle is known scientifically as the hydrologic cycle. ... A coral reef near the Hawaiian islands is an example of a complex marine ecosystem. ... For other uses, see River (disambiguation). ... Sandy Bay is a small bay on the eastern side of Gibraltar, on the far side of the Rock from the main city. ... An ecoregion is a relatively large area of land or water that contains a geographically distinct assemblage of natural communities. ... A biome is a climatically and geographically defined area of ecologically similar communities of plants, animals, and soil organisms, often referred to as ecosystems. ...

In the Gaia hypothesis, James Lovelock stated that the entire mass of living matter on Earth (or any planet with life) functions as a vast homeostatic superorganism that actively modifies its planetary environment to produce the environmental conditions necessary for its own survival. In this view, the entire planet maintains homeostasis. Whether this sort of system is present on Earth is still open to debate. However, some relatively simple homeostatic mechanisms are generally accepted. For example, when atmospheric carbon dioxide levels rise, certain plants are able to grow better and thus act to remove more carbon dioxide from the atmosphere. When sunlight is plentiful and atmospheric temperature climbs, the phytoplankton of the ocean surface waters thrive and produce more dimethyl sulfide, DMS. The DMS molecules act as cloud condensation nuclei, which produce more clouds, and thus increase the atmospheric albedo and this feeds back to lower the temperature of the atmosphere. As scientists discover more about Gaia, vast numbers of positive and negative feedback loops are being discovered, that, together, maintain a metastable condition, sometimes within very broad range of environmental conditions. For other uses, see Gaia. ... Dr. James Ephraim Lovelock, CH, CBE, FRS (born 26 July 1919) is an independent scientist, author, researcher, environmentalist, and futurologist who lives in Cornwall, in the south west of Great Britain. ... A group of organisms, such as an insect colony, that functions as a social unit. ... Diagrams of some typical phytoplankton Phytoplankton are the autotrophic component of plankton. ... Dimethyl sulfide causes that distinctive smell from your St. ... Aerosol pollution over Northern India and Bangladesh - NASA Cloud condensation nuclei or CCNs (also known as cloud seeds) are small particles (typically 0. ... For other uses, see Albedo (disambiguation). ...

Reactive homeostasis

Example of use: "Reactive homeostasis is an immediate response to a homeostatic challenge such as predation."

However, any homeostasis is impossible without reaction - because homeostasis is and must be a "feedback" phenomenon.

The phrase "reactive homeostasis" is simply short for: "reactive compensation reestablishing homeostasis", that is to say, "reestablishing a point of homeostasis." - it should not be confused with a separate kind of homeostasis or a distinct phenomenon from homeostasis; it is simply the compensation (or compensatory) phase of homeostasis.

Other fields

The term has come to be used in other fields, as well.

Risk homeostasis

Main article: risk homeostasis

An actuary may refer to risk homeostasis, where (for example) people that have anti-lock brakes have no better safety record than those without anti-lock brakes, because the former unconsciously compensate for the safer vehicle via less-safe driving habits. Previous to the innovation of anti-lock brakes, certain maneuvers involved minor skids, evoking fear and avoidance: now the anti-lock system moves the boundary for such feedback, and behavior patterns expand into the no-longer punitive area. It has also been suggested that ecological crises are an instance of risk homeostasis in which behavior known to be dangerous continues until dramatic consequences actually occur. Risk homeostasis is a psychological theory developed by Gerald J.S. Wilde, a professor emeritus of psychology at Queens University, Kingston, Ontario, Canada. ... Damage from Hurricane Katrina. ...

Stress homeostasis

Sociologists and psychologists may refer to stress homeostasis, the tendency of a population or an individual to stay at a certain level of stress, often generating artificial stresses if the "natural" level of stress is not enough.^{[citation needed]}

Jean Francois Lyotard, a postmodern theorist, has applied this term to societal 'power centers' that he describes as being 'governed by a principle of homeostasis,' for example, the scientific hierarchy, which will sometimes ignore a radical new discovery for years because it destabilizes previously-accepted norms. (See "The Postmodern Condition: A Report on Knowledge" by J.F. Lyotard)

Waste homeostasis

Andrew Potter has used the term waste homeostasis in reference to the lack of net gain from energy-saving technologies.^[3] one of several front covers The Rebel Sell: Why the culture cant be jammed is the name of a popular non-fiction book written by Canadian authors Joseph Heath and Andrew Potter in 2004. ... The term Rebound effect is used in innovation theory/green marketing to refer to the increases of demand that are caused by the introduction of more efficient/environmentally sound technologies. ...

Conversational homeostasis

A 2007 study purported to find (and show clinically) conversational homeostasis in which overly-familiar people (such as spouses) condense their speech so much that they are actually worse at communicating novel information than strangers are, while not being conscious of this problem. ^[4]

Metabolic homeostasis

Some herbal medicines, known as adaptogens, have been defined to function as non-toxic metabolic regulators that can enhance metabolic homeostasis during stress.^[5] The word adaptogen is used by herbalists to refer to a natural herb product that increases the bodys resistance to stresses such as trauma, anxiety and bodily fatigue. ...

See also

Two alpinists Acclimatization is the process of an organism adjusting to chronic change in its environment, often involving temperature, moisture, food, often relating to seasonal climate changes. ... Allostasis is the process of achieving stability, or homeostasis, through physiological or behavioral change. ... A section of mouse liver showing an apoptotic cell indicated by an arrow Apoptosis (/̩æ.pəpˈto. ... A biorhythm (or biological rhythm) is a cyclic pattern of alterations in physiology, emotions, and/or intellect. ... For the 17th Century Roman Catholic priest who popularized the Memorare, see Father Claude Bernard. ... For other uses, see Cybernetics (disambiguation). ... Enantiostasis is the ability of an open system, especially a living organism, to stabilize and conserve function in spite of an unstable environment. ... For other uses, see Gaia. ... Homeorhesis, derived from the Greek for similar flow, is a concept encompassing dynamical systems which return to a trajectory, as opposed to systems which return to a particular state, which is termed homeostasis. ... Structure of the coenzyme adenosine triphosphate, a central intermediate in energy metabolism. ... Osmosis is the spontaneous net movement of water across a semipermeable membrane from a region of low solute concentration to a solution with a high solute concentration, down a solute concentration gradient. ... A protobiont is an aggregate of abiotically produced organic molecules, that has been demonstrated to be formed by self assembly. ... Self-organization refers to a process in which the internal organization of a system, normally an open system, increases automatically without being guided or managed by an outside source. ... In biology, senescence is the combination of processes of deterioration which follow the period of development of an organism. ... Steady state has a number of meanings: In biochemistry, steady state is a central term in enzyme kinetics. ... Lenzs law (pronounced (IPA) ) gives the direction of the induced electromotive force (emf) and current resulting from electromagnetic induction. ... In chemistry, Le Chateliers principle, also called the Le Chatelier-Braun principle, can be used to predict the effect of a change in conditions on a chemical equilibrium. ...

References