Publicité E▼
endorphin (n.)
1.a neurochemical occurring naturally in the brain and having analgesic properties
Endorphin (n.)
1.(MeSH)One of the three major groups of endogenous opioid peptides. They are large peptides derived from the PRO-OPIOMELANOCORTIN precursor. The known members of this group are alpha-, beta-, and gamma-endorphin. The term endorphin is also sometimes used to refer to all opioid peptides, but the narrower sense is used here; OPIOID PEPTIDES is used for the broader group.
Publicité ▼
⇨ voir la définition de Wikipedia
Endorphin (n.) (MeSH)
Publicité ▼
⇨ ACTH-Endorphin Precursor • Endorphin Receptor • Endorphin Receptors • Endorphin, alpha • Endorphin, beta • Endorphin, gamma • Endorphin-ACTH Precursor • Pro-ACTH-Endorphin • Receptors, Endorphin • Receptors, beta-Endorphin • alpha-Endorphin • beta endorphin • beta-Endorphin • beta-Endorphin (1-16) • beta-Endorphin (1-17) • beta-Endorphin (1-31) • beta-Endorphin Receptor • gamma-Endorphin
⇨ Beta endorphin • Beta-endorphin • Embrace (Endorphin album) • Endorphin (Australian band) • Endorphin (disambiguation) • Endorphin (software) • Endorphin rush • Skin (Endorphin album)
Wikipedia
Endorphins ("endogenous morphine") are endogenous opioid peptides that function as neurotransmitters.[1] They are produced by the pituitary gland and the hypothalamus in vertebrates during exercise,[2] excitement, pain, consumption of spicy food, love and orgasm,[3][4] and they resemble the opiates in their abilities to produce analgesia and a feeling of well-being.
The term implies a pharmacological activity (analogous to the activity of the corticosteroid category of biochemicals) as opposed to a specific chemical formulation. It consists of two parts: endo- and -orphin; these are short forms of the words endogenous and morphine, intended to mean "a morphine-like substance originating from within the body."[5]
The term "endorphin rush" has been adopted in popular speech to refer to feelings of exhilaration brought on by pain, danger, or other forms of stress,[2] supposedly due to the influence of endorphins. When a nerve impulse reaches the spinal cord, endorphins that prevent nerve cells from releasing more pain signals are released. Immediately after injury, endorphins allow animals to feel a sense of power and control over themselves that allows them to persist with activity for an extended time.[citation needed]
Contents |
Opioid neuropeptides were first discovered in 1974 by two independent groups of investigators:
β-Endorphin is released into blood from the pituitary gland and into the spinal cord and brain from hypothalamic neurons. The β-endorphin that is released into the blood cannot enter the brain in large quantities because of the blood–brain barrier, so the physiological importance of the β-endorphin that can be measured in the blood is far from clear. β-Endorphin is a cleavage product of pro-opiomelanocortin (POMC), which is also the precursor hormone for adrenocorticotrophic hormone (ACTH). The behavioural effects of β-endorphin are exerted by its actions in the brain and spinal cord, and it is presumed that the hypothalamic neurons are the major source of β-endorphin at these sites. In situations where the level of ACTH is increased (e.g., Cushing’s Syndrome), the level of endorphins also increases slightly.
β-Endorphin has the highest affinity for the μ1 opioid receptor, slightly lower affinity for the μ2 and δ opioid receptors, and low affinity for the κ1 opioid receptors. μ-Opioid receptors are the main receptor through which morphine acts. In the classical sense, μ opioid receptors are presynaptic, and inhibit neurotransmitter release; through this mechanism, they inhibit the release of the inhibitory neurotransmitter GABA, and disinhibit the dopamine pathways, causing more dopamine to be released. By hijacking this process, exogenous opioids cause inappropriate dopamine release, and lead to aberrant synaptic plasticity, which causes dependency. Opioid receptors have many other and more important roles in the brain and periphery however, modulating pain, cardiac, gastric and vascular function as well as possibly panic and satiation, and receptors are often found at postsynaptic locations as well as presynaptically.
Scientists sometimes debate whether specific activities release measurable levels of endorphins. Much of the current data comes from animal models which may not be relevant to humans. The studies that do involve humans often measure endorphin plasma levels, which do not necessarily correlate with levels in the central nervous system. Other studies use a blanket opioid antagonist (usually naloxone) to indirectly measure the release of endorphins by observing the changes that occur when any endorphin activity that might be present is blocked.
A publicized effect of endorphin production is the so-called "runner's high", which is said to occur when strenuous exercise takes a person over a threshold that activates endorphin production. Endorphins are released during long, continuous workouts, when the level of intensity is between moderate and high, and breathing is difficult. This also corresponds with the time that muscles use up their stored glycogen. During a release of endorphins, the person may be exposed to bodily harm from strenuous bodily functions after going past his or her body's physical limit. This means that runners can keep running despite pain, continuously surpassing what they otherwise would consider to be their limit. Runner's high has also been known to create feelings of euphoria and happiness.
Runner's high has been suggested to have evolutionary roots based on the theory that it helped with the survival of early humans. Runner's high allows humans to run for vast lengths without pain.[citation needed] Most early humans hunted and gathered for their food. This required them to cover long distances hunting down their prey or foraging for their food. This could have caused them to develop conditions such as shin splints and stress fractures in their shin and feet bones. Without runner's high to negate the pain caused by running on bones with these conditions, early humans theoretically would not have been able to repeatedly cover these vast distances in search of their food and thus would have starved. Current African tribes make use of runner's high when conducting persistence hunting. Persistence hunting is a method of hunting in which tribesman hunt an animal and track it for many miles, eventually killing the animal due to its vulnerability brought on by exhaustion.[11]
In 2008, researchers in Germany reported on the mechanisms that cause the runner's high. Using PET scans combined with recently available chemicals that reveal endorphins in the brain, they were able to compare runners’ brains before and after a run.[12]
It is also suggested by many[who?] that endorphins are some of the many chemicals that contribute to runner's high; other candidates include epinephrine, serotonin, and dopamine.
Previous research on the role of endorphins in producing runner's high questioned the mechanisms at work, their data possibly demonstrated that the "high" comes from completing a challenge rather than as a result of exertion.[13] Studies in the early 1980s cast doubt on the relationship between endorphins and the runner's high for several reasons:
Endorphins are known to play a role in depersonalization disorder. The opioid antagonists naloxone and naltrexone have both been proven to be successful in treating depersonalization.[18][19] To quote a 2001 naloxone study, "In three of 14 patients, depersonalization symptoms disappeared entirely and seven patients showed a marked improvement. The therapeutic effect of naloxone provides evidence for the role of the endogenous opioid system in the pathogenesis of depersonalization."
In 2003, clinical researchers reported that profound relaxation in a float tank triggers the production of endorphins.[20] This explains the pain relief experienced during float sessions.[21]
In 1999, clinical researchers reported that inserting acupuncture needles into specific body points triggers the production of endorphins.[22][23] In another study, higher levels of endorphins were found in cerebrospinal fluid after patients underwent acupuncture.[24] In addition, naloxone appeared to block acupuncture’s pain-relieving effects.
A placental tissue of fetal origin — i.e., the syncytiotrophoblast — excretes beta-endorphins into the maternal blood system from the 3rd month of pregnancy. A recent study[25] proposes an adaptive background for this phenomenon. The authors argue that fetuses make their mothers endorphin-dependent then manipulate them to increase nutrient allocation to the placenta. Their hypothesis predicts that: (1) anatomic position of endorphin production should mirror its presumed role in foetal-maternal conflict; (2) endorphin levels should co-vary positively with nutrient carrying capacity of maternal blood system; (3) postpartum psychological symptoms (such as postpartum blues, depression, and psychosis) in humans are side-effects of this mechanism that can be interpreted as endorphin-deprivation symptoms; (4) shortly after parturition, placentophagy could play an adaptive role in decreasing the negative side-effects of foetal manipulation; (5) later, breast-feeding-induced endorphin excretion of the maternal pituitary saves mother from further deprivation symptoms. These predictions appear to be supported by empirical data.[25]
From the Greek: word endo ενδο meaning "within" (endogenous, Greek: ενδογενής, "proceeding from within") and morphine, from Morpheus, Greek: Μορφέας, the god of sleep in the Greek mythology, thus 'endo(genous) (mo)rphine’.
|
Contenu de sensagent
dictionnaire et traducteur pour sites web
Alexandria
Une fenêtre (pop-into) d'information (contenu principal de Sensagent) est invoquée un double-clic sur n'importe quel mot de votre page web. LA fenêtre fournit des explications et des traductions contextuelles, c'est-à-dire sans obliger votre visiteur à quitter votre page web !
Essayer ici, télécharger le code;
SensagentBox
Avec la boîte de recherches Sensagent, les visiteurs de votre site peuvent également accéder à une information de référence pertinente parmi plus de 5 millions de pages web indexées sur Sensagent.com. Vous pouvez Choisir la taille qui convient le mieux à votre site et adapter la charte graphique.
Solution commerce électronique
Augmenter le contenu de votre site
Ajouter de nouveaux contenus Add à votre site depuis Sensagent par XML.
Parcourir les produits et les annonces
Obtenir des informations en XML pour filtrer le meilleur contenu.
Indexer des images et définir des méta-données
Fixer la signification de chaque méta-donnée (multilingue).
Renseignements suite à un email de description de votre projet.
Jeux de lettres
Les jeux de lettre français sont :
○ Anagrammes
○ jokers, mots-croisés
○ Lettris
○ Boggle.
Lettris
Lettris est un jeu de lettres gravitationnelles proche de Tetris. Chaque lettre qui apparaît descend ; il faut placer les lettres de telle manière que des mots se forment (gauche, droit, haut et bas) et que de la place soit libérée.
boggle
Il s'agit en 3 minutes de trouver le plus grand nombre de mots possibles de trois lettres et plus dans une grille de 16 lettres. Il est aussi possible de jouer avec la grille de 25 cases. Les lettres doivent être adjacentes et les mots les plus longs sont les meilleurs. Participer au concours et enregistrer votre nom dans la liste de meilleurs joueurs ! Jouer
Dictionnaire de la langue française
Principales Références
La plupart des définitions du français sont proposées par SenseGates et comportent un approfondissement avec Littré et plusieurs auteurs techniques spécialisés.
Le dictionnaire des synonymes est surtout dérivé du dictionnaire intégral (TID).
L'encyclopédie française bénéficie de la licence Wikipedia (GNU).
Copyright
Les jeux de lettres anagramme, mot-croisé, joker, Lettris et Boggle sont proposés par Memodata.
Le service web Alexandria est motorisé par Memodata pour faciliter les recherches sur Ebay.
La SensagentBox est offerte par sensAgent.
Traduction
Changer la langue cible pour obtenir des traductions.
Astuce: parcourir les champs sémantiques du dictionnaire analogique en plusieurs langues pour mieux apprendre avec sensagent.
calculé en 0,062s