Hormones are endogenous substances secreted in the body, with different biological roles and functions
Endogenous substances and processes are those that originate from within a system such as an organism, tissue, or cell.[1] The term is chiefly used in biology but also in other fields.[nb 1]
Endogenous substances and processes contrast with exogenous ones, such as drugs, which originate from outside of the organism.
Endogenous substances
Cell signalling systems such as hormone and neurotransmitter systems use endogenous substances. Endogenous substances can regulate sleep.[2]: 1 Examples of endogenous substances, and systems that use them, include
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.[3]
Endogenous opioids, which are peptides, such as enkephalins and endorphins, that can modulate the opioid system.[5] The term "endorphin" is derived from "endogenous morphine".
Nitric oxide, which is an endogenous cell signalling molecule.[6] 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 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.
Endogenous effects can modulate and regulate systems, in conjunction with environmental influences.[9]: 8
Endogeny can refer to changes that originate from within a system.[9]: 8 Endogenous changes can occur in social systems and can be modelled by Marxian dialectics.[9]: 8
Orthogenesis is a similar concept to endogeny but refers to changes within separate systems that results in their evolution along similar paths.[9]: 8 The concept of orthogenesis has never been widely favored in evolutionary biology.[9]: 8
Endogenous biological clocks and biological rhythms originating from endogenous mechanisms allow forms of biochronometry.[10]: 281–282
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.
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
Anemotionorbehavior is endogenous if it is spontaneously generated from an individual's internal state.
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
Inpolitical science, something is endogenous if it is actually the result of the action for which it is generally labeled the cause[citation needed]. 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.
^Akil, Huda; Watson, Stanley J.; Young, Elizabeth; Lewis, Michael E.; Khachaturian, Henry; Walker, J. Michael (1984). "Endogenous Opioids: Biology and Function". Annual Review of Neuroscience. 7 (1): 223–255. doi:10.1146/annurev.ne.07.030184.001255. PMID6324644.
^Chen S, Zheng S, Liu Z, Tang C, Zhao B, Du J, Jin H (Feb 2015). "Endogenous sulfur dioxide protects against oleic acid-induced acute lung injury in association with inhibition of oxidative stress in rats". Lab. Invest. 95 (2): 142–156. doi:10.1038/labinvest.2014.147. PMID25581610.