Exogenous
Encyclopedia
Exogenous refers to an action or object coming from outside a system. It is the opposite of endogenous
, something generated from within the system.
Endogenous
Endogenous substances are those that originate from within an organism, tissue, or cell. Endogenous retroviruses are caused by ancient infections of germ cells in humans, mammals and other vertebrates...
, something generated from within the system.
- In an economicEconomicsEconomics is the social science that analyzes the production, distribution, and consumption of goods and services. The term economics comes from the Ancient Greek from + , hence "rules of the house"...
modelModel (economics)In economics, a model is a theoretical construct that represents economic processes by a set of variables and a set of logical and/or quantitative relationships between them. The economic model is a simplified framework designed to illustrate complex processes, often but not always using...
, an exogenous change is one that comes from outside the model and is unexplained by the model. For example, in the simple supply and demandSupply and demandSupply and demand is an economic model of price determination in a market. It concludes that in a competitive market, the unit price for a particular good will vary until it settles at a point where the quantity demanded by consumers will equal the quantity supplied by producers , resulting in an...
model, a change in consumer tastes or preferences is unexplained by the model and also leads to endogenousEndogenousEndogenous substances are those that originate from within an organism, tissue, or cell. Endogenous retroviruses are caused by ancient infections of germ cells in humans, mammals and other vertebrates...
changes in demand that lead to changes in the equilibriumEconomic equilibriumIn economics, economic equilibrium is a state of the world where economic forces are balanced and in the absence of external influences the values of economic variables will not change. It is the point at which quantity demanded and quantity supplied are equal...
price. Similarly, a change in the consumer's income is given outside the model. Put another way, an exogenous change involves an alteration of a variable that is autonomous, i.e., unaffected by the workings of the modelModel (economics)In economics, a model is a theoretical construct that represents economic processes by a set of variables and a set of logical and/or quantitative relationships between them. The economic model is a simplified framework designed to illustrate complex processes, often but not always using...
.
- In linear regressionLinear regressionIn statistics, linear regression is an approach to modeling the relationship between a scalar variable y and one or more explanatory variables denoted X. The case of one explanatory variable is called simple regression...
, it means that the variable is independent of all other response values.
- In biologyBiologyBiology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
, "exogenous" refers to an action or object coming from the outside of a system. For example, an exogenous contrast agent in medical imaging refers to a liquid injected into the patient intravenously that enhances visibility of a pathology, such as a tumorTumorA tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
.
- In biologyBiologyBiology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
, an exogenous factor is any material that is present and active in an individual organismOrganismIn biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
or living cellCell (biology)The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
but that originated outside of that organism, as opposed to an endogenous factor.- Exogenous factors in medicineMedicineMedicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
include both pathogens and therapeutics. - DNADNADeoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
introduced to cells via transfectionTransfectionTransfection is the process of deliberately introducing nucleic acids into cells. The term is used notably for non-viral methods in eukaryotic cells...
or viral infection (transductionTransduction (genetics)Transduction is the process by which DNA is transferred from one bacterium to another by a virus. It also refers to the process whereby foreign DNA is introduced into another cell via a viral vector. Transduction does not require cell-to-cell contact , and it is DNAase resistant...
) is an exogenous factor. - Carcinogens are exogenous factors.
- Exogenous factors in medicine
- The word exogenous is also used in geographyGeographyGeography is the science that studies the lands, features, inhabitants, and phenomena of Earth. A literal translation would be "to describe or write about the Earth". The first person to use the word "geography" was Eratosthenes...
. Exogenous processes are all taking place at the outside of the EarthEarthEarth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
and all the other planets. WeatheringWeatheringWeathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...
, erosionErosionErosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
, transportation and sedimentationSedimentationSedimentation is the tendency for particles in suspension to settle out of the fluid in which they are entrained, and come to rest against a barrier. This is due to their motion through the fluid in response to the forces acting on them: these forces can be due to gravity, centrifugal acceleration...
are the main exogenous processes.
- In attentional psychologyPsychologyPsychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...
, exogenous refers to reaction to external stimuli without conscious intention. An example of this would be attention drawn to a flashing light in the periphery of visionVisual perceptionVisual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...
.
- In ludology, the study of games, exogenous refers to anything outside the game itself. Therefore an item in a Massively Multiplayer Online Game would have exogenous value if people were buying it with real world money rather than in game currency (though its in game cost would be endogenousEndogenousEndogenous substances are those that originate from within an organism, tissue, or cell. Endogenous retroviruses are caused by ancient infections of germ cells in humans, mammals and other vertebrates...
).
- In materials scienceMaterials scienceMaterials science is an interdisciplinary field applying the properties of matter to various areas of science and engineering. This scientific field investigates the relationship between the structure of materials at atomic or molecular scales and their macroscopic properties. It incorporates...
, exogenous refers to a property of a substance which is derived from outside or external influences, such as a nano-doped material.