Endogeny (biology)
Endogeny (biology)
Endogenous substances and processes contrast with exogenous ones, such as drugs, which originate from outside of the organism.
Endogenous substances
The endogenous cannabinoid system, from which the term "endocannabinoid" derives. The endocannabinoid system is important in physiology but can be modulated by exogenous phytocannabinoids originating from outside the organism, such as THC.[4]
Endogenous opioids, which are peptides, such as enkephalins and endorphins, that can modulate the opioid system.[6] The term "endorphin" is derived from "endogenous morphine".
Nitric oxide, which is an endogenous cell signalling molecule.[7] Nitric oxide was identified as the substance previously known as endothelium-derived relaxing factor (EDRF), which was known to be an endogenous substance responsible for the relaxation of vascular endothelium.
Endogenous transcription factors are those manufactured by the cell, as distinguished from cloned transcription factors.
Endogenous substances typically have some physiological utility. However substances can also be pathologically endogenous. For example, in auto-brewery syndrome, ethanol is endogenously produced within the digestive system through endogenous fermentation of sugars.
Endogeneity can, in some biological systems, particularly with viruses and prokaryotes, pertain to DNA incorporated (endogenized) into the organism.[9] However, because of homeostasis, discerning between internal and external influences is often difficult. Endogenous viral elements, which are DNA sequences derived from viruses that are ancestrally inserted into the genomes of germ cells. These sequences, which may be fragments of viruses or entire viral genomes (proviruses), can persist in the germline, being passed on from one generation to the next as host alleles. Endogenous retroviruses are a type of endogenous viral element.
Endogenous processes
Examples of endogenous processes include:
Senescence (biological aging)
The menstrual cycle
The self-sustained circadian rhythms of plants and animals.
Endogenous regeneration, which refers to the ability of cells to engage in the repair and regeneration process.
Endogenous biological clocks and biological rhythms originating from endogenous mechanisms allow forms of biochronometry.[11] []
Endogenous processes can also be pathological. For example, endogenous depression is an atypical type of depression caused by internal effects, such as cognitive and biological stressors.
Endogeneity in other fields
Geography
All processes that take place inside Earth (and other planets) are considered endogenous. They make the continents migrate, push the mountains up, and trigger earthquakes and volcanism. Endogenous processes are driven by the warmth that is produced in the core of Earth by radioactivity and gravity.
Psychology
Economics and finance
A variable is called endogenous if it is explained within the model in which it appears. For example, in a supply and demand model of an agricultural market, the price and quantity of trade would be the endogenous variables explained by the model; changes in the weather or in consumer tastes would be exogenous variables that might shift the supply and demand curves.
Political science
In political science, something is endogenous if it is actually the result of the action for which it is generally labeled the cause. For example, ethnic violence is generally thought to be caused by ethnic division. However, endogeny would say that ethnic divisions are a result of ethnic violence.
See also
Endogeneity (econometrics)
Endogenous preferences
Endogenous growth theory
Endocrine system
Exogeny