The area postrema is a structure in the medulla oblongata in the brainstem that controls vomiting. Its location in the brain allows it to play a vital role in the control of autonomic functions by the central nervous system, it is one of the circumventricular organs, enabling the dual role of being a sensor for circulating chemical messengers in the blood, as well as integrating neural inputs in the brainstem. The area postrema is a small protuberance found at the inferoposterior limit of the fourth ventricle. Specialized ependymal cells are found within the area postrema; these specialized ependymal cells differ from the majority of ependymal cells, forming a unicellular epithelium lining of the ventricles and central canal. The area postrema is separated from the vagal triangle by the funiculus separans, a thin semitransparent ridge; the vagal triangle overlies the dorsal vagal nucleus and is situated on the caudal end of the rhomboid fossa or'floor' of the fourth ventricle. The area postrema is situated just before the obex, the inferior apex of the caudal ventricular floor.
Both the funiculus separans and area postrema have a similar thick ependyma-containing tanycyte covering. Ependyma and tanycytes can participate in transport of neurochemicals into and out of the cerebrospinal fluid from its cells or adjacent neurons, glia or vessels. Ependyma and tanycytes may participate in chemoreception; the eminence of the area postrema is considered a circumventricular organ because its endothelial cells do not contain tight junctions, which allows for free exchange of molecules between blood and brain tissue. This unique breakdown in the blood–brain barrier is compensated for by the presence of a tanycyte barrier; the area postrema connects to the solitary nucleus and other autonomic control centers in the brainstem. It is excited by visceral afferent impulses arising from the gastrointestinal tract and other peripheral trigger zones, by humoral factors; the area postrema makes up part of the dorsal vagal complex, the critical termination site of vagal afferent nerve fibers, along with the dorsal motor nucleus of the vagus and the SN.
Nausea is most induced via stimulation of the area postrema via its connection to the SN, which may serve as the beginning of the pathway triggering vomiting in response to various emetic inputs. However, this structure plays no key role for nausea induced by the activation of vagal nerve fibers or by motion, its function in radiation-induced vomiting remains unclear; because the area postrema and a specialized region of SN have permeable capillaries and other hormonal signals in the blood have direct access to neurons of brain areas with vital roles in the autonomic control of the body. As a result, the area postrema is considered a site of integration for various physiological signals in the blood as they enter the central nervous system; the area postrema, one of the circumventricular organs, detects toxins in the blood and acts as a vomit-inducing center. The area postrema is a critical homeostatic integration center for humoral and neural signals by means of its function as a chemoreceptor trigger zone for vomiting in response to emetic drugs.
It is a densely vascularized structure that lacks tight junctions between capillary endothelial cells, thereby having high permeability to circulating blood signals, allowing it to detect various chemical messengers in the blood and cerebrospinal fluid. Capillary blood flow appears to be uniquely slow in the area postrema, prolonging the contact time for blood-borne hormones to interact with neuronal receptors involved in regulation of blood pressure, body fluids, emetic responses; the fenestrated capillaries of the area postrema and a specialized region of the nucleus tractus solitarii makes this particular region of the medulla critical in the autonomic control of various physiological systems, including the cardiovascular system and the systems controlling feeding and metabolism. Angiotensin II causes a dose-dependent increase in arterial blood pressure without producing considerable changes in the heart rate, an effect mediated by the area postrema. Damage to the area postrema, caused by lesioning or ablation, prevents the normal functions of the area postrema from taking place.
This ablation is done surgically and for the purpose of discovering the exact effect of the area postrema on the rest of the body. Since the area postrema acts as an entry point to the brain for information from the sensory neurons of the stomach, liver, kidneys and other internal organs, a variety of physiological reflexes rely on the area postrema to transfer information; the area postrema acts to directly monitor the chemical status of the organism. Lesions of the area postrema are sometimes referred to as'central vagotomy' because they eliminate the brain’s ability to monitor the physiological status of the body through its vagus nerve; these lesions thus serve to prevent the detection of poisons and prevent the body’s natural defenses from kicking in. In one example, experiments done by Bernstein et al. on rats indicated that the area postrema lesions prevented the detection of lithium chloride, which can become toxic at high concentrations. Since the rats could not detect the chemical, they were not able to employ a psychological procedure known as taste aversion conditioning, causing the rat to continuously ingest the lithium-paired saccharin solution.
These findings indicate that rats with area postrema lesions do not acquire the normal conditioned taste aversions when lithium chloride is used as the unconditioned stimulus. In addition to simple taste aversions, rats with the area postrema lesions failed to perform other behavioral and physiological responses associa
Opiate is a term classically used in pharmacology to mean a drug derived from opium. Opioid, a more modern term, is used to designate all substances, both natural and synthetic, that bind to opioid receptors in the brain. Opiates are alkaloid compounds found in the opium poppy plant Papaver somniferum; the psychoactive compounds found in the opium plant include morphine and thebaine. Opiates are considered drugs with moderate to high abuse potential and are listed on various "Substance-Control Schedules" under the Uniform Controlled Substances Act of the United States of America. In 2014, between 13 and 20 million people used opiates recreationally. Opiates belong to the large biosynthetic group of benzylisoquinoline alkaloids, are so named because they are occurring alkaloids found in the opium poppy; the major psychoactive opiates are morphine and thebaine. Papaverine, 24 other alkaloids are present in opium but have little to no effect on the human central nervous system, as such are not considered to be opiates.
Small quantities of hydrocodone and hydromorphone are detected in assays of opium on rare occasions. Dihydrocodeine, oxycodone, oxymorphone and other derivatives of morphine and/or hydromorphone are found in trace amounts in opium. Despite morphine being the most medically significant opiate, larger quantities of codeine are consumed medically, most of it synthesized from morphine. Codeine has more predictable oral bioavailability, making it easier to titrate the dose. Codeine has less abuse potential than morphine, because it is milder, larger doses of codeine are required. Opiate withdrawal syndrome effects are associated with the abrupt cessation or reduction of prolonged opiate usage. While the full synthesis of opioids from naphthoquinone or other simple organic starting materials is possible, they are tedious and uneconomical processes. Therefore, most of the opiate-type analgesics in use today are either extracted from Papaver somniferum or synthesized from those opiates thebaine. In 2015 researches reported successful biosynthesis of thebaine and hydrocodone using genetically modified yeast.
Once scaled for commercial use the process would cut production time from a year to several days and could reduce costs by 90%. Heroin is one of several semi-synthetic opioids derived from the morphine. Although sometimes not considered opiates, as they are not directly derived from natural opium, they are referred to as opiates. Heroin is a morphine prodrug. One of the major metabolites of heroin, 6-monoacetylmorphine, is a morphine prodrug. Nicomorphine, dipropanoylmorphine, methyldesorphine, acetylpropionylmorphine, dibenzoylmorphine, diacetyldihydromorphine, several others are derived from morphine. Opiate comparison Opioid epidemic World Health Organization guidelines for the availability and accessibility of controlled substances
Europe is a continent located in the Northern Hemisphere and in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west and the Mediterranean Sea to the south, it comprises the westernmost part of Eurasia. Since around 1850, Europe is most considered to be separated from Asia by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas and the waterways of the Turkish Straits. Although the term "continent" implies physical geography, the land border is somewhat arbitrary and has been redefined several times since its first conception in classical antiquity; the division of Eurasia into two continents reflects East-West cultural and ethnic differences which vary on a spectrum rather than with a sharp dividing line. The geographic border does not follow political boundaries, with Turkey and Kazakhstan being transcontinental countries. A strict application of the Caucasus Mountains boundary places two comparatively small countries and Georgia, in both continents.
Europe covers 2 % of the Earth's surface. Politically, Europe is divided into about fifty sovereign states of which the Russian Federation is the largest and most populous, spanning 39% of the continent and comprising 15% of its population. Europe had a total population of about 741 million as of 2016; the European climate is affected by warm Atlantic currents that temper winters and summers on much of the continent at latitudes along which the climate in Asia and North America is severe. Further from the sea, seasonal differences are more noticeable than close to the coast. Europe, in particular ancient Greece, was the birthplace of Western civilization; the fall of the Western Roman Empire in 476 AD and the subsequent Migration Period marked the end of ancient history and the beginning of the Middle Ages. Renaissance humanism, exploration and science led to the modern era. Since the Age of Discovery started by Portugal and Spain, Europe played a predominant role in global affairs. Between the 16th and 20th centuries, European powers controlled at various times the Americas all of Africa and Oceania and the majority of Asia.
The Age of Enlightenment, the subsequent French Revolution and the Napoleonic Wars shaped the continent culturally and economically from the end of the 17th century until the first half of the 19th century. The Industrial Revolution, which began in Great Britain at the end of the 18th century, gave rise to radical economic and social change in Western Europe and the wider world. Both world wars took place for the most part in Europe, contributing to a decline in Western European dominance in world affairs by the mid-20th century as the Soviet Union and the United States took prominence. During the Cold War, Europe was divided along the Iron Curtain between NATO in the West and the Warsaw Pact in the East, until the revolutions of 1989 and fall of the Berlin Wall. In 1949 the Council of Europe was founded, following a speech by Sir Winston Churchill, with the idea of unifying Europe to achieve common goals, it includes all European states except for Belarus and Vatican City. Further European integration by some states led to the formation of the European Union, a separate political entity that lies between a confederation and a federation.
The EU originated in Western Europe but has been expanding eastward since the fall of the Soviet Union in 1991. The currency of most countries of the European Union, the euro, is the most used among Europeans. In classical Greek mythology, Europa was a Phoenician princess; the word Europe is derived from her name. The name contains the elements εὐρύς, "wide, broad" and ὤψ "eye, countenance", hence their composite Eurṓpē would mean "wide-gazing" or "broad of aspect". Broad has been an epithet of Earth herself in the reconstructed Proto-Indo-European religion and the poetry devoted to it. There have been attempts to connect Eurṓpē to a Semitic term for "west", this being either Akkadian erebu meaning "to go down, set" or Phoenician'ereb "evening, west", at the origin of Arabic Maghreb and Hebrew ma'arav. Michael A. Barry, professor in Princeton University's Near Eastern Studies Department, finds the mention of the word Ereb on an Assyrian stele with the meaning of "night, sunset", in opposition to Asu " sunrise", i.e. Asia.
The same naming motive according to "cartographic convention" appears in Greek Ἀνατολή. Martin Litchfield West stated that "phonologically, the match between Europa's name and any form of the Semitic word is poor." Next to these hypotheses there is a Proto-Indo-European root *h1regʷos, meaning "darkness", which produced Greek Erebus. Most major world languages use words derived from Europa to refer to the continent. Chinese, for example, uses the word Ōuzhōu. In some Turkic languages the Persian name Frangistan is used casually in referring to much of Europe, besides official names such as Avrupa or Evropa; the prevalent definition of Europe as a geographical term has been in use since the mid-19th century. Europe is taken to be bounded by large bodies of water
The Middle East is a transcontinental region centered on Western Asia and Egypt. Saudi Arabia is geographically the largest Middle Eastern nation; the corresponding adjective is Middle Eastern and the derived noun is Middle Easterner. The term has come into wider usage as a replacement of the term Near East beginning in the early 20th century. Arabs, Persians and Azeris constitute the largest ethnic groups in the region by population. Arabs constitute the largest ethnic group in the region by a clear margin. Indigenous minorities of the Middle East include Jews, Assyrians, Copts, Lurs, Samaritans, Shabaks and Zazas. European ethnic groups that form a diaspora in the region include Albanians, Circassians, Crimean Tatars, Franco-Levantines, Italo-Levantines. Among other migrant populations are Chinese, Indians, Pakistanis, Pashtuns and sub-Saharan Africans; the history of the Middle East dates back to ancient times, with the importance of the region being recognized for millennia. Several major religions have their origins in the Middle East, including Judaism and Islam.
The Middle East has a hot, arid climate, with several major rivers providing irrigation to support agriculture in limited areas such as the Nile Delta in Egypt, the Tigris and Euphrates watersheds of Mesopotamia, most of what is known as the Fertile Crescent. Most of the countries that border the Persian Gulf have vast reserves of crude oil, with monarchs of the Arabian Peninsula in particular benefiting economically from petroleum exports; the term "Middle East" may have originated in the 1850s in the British India Office. However, it became more known when American naval strategist Alfred Thayer Mahan used the term in 1902 to "designate the area between Arabia and India". During this time the British and Russian Empires were vying for influence in Central Asia, a rivalry which would become known as The Great Game. Mahan realized not only the strategic importance of the region, but of its center, the Persian Gulf, he labeled the area surrounding the Persian Gulf as the Middle East, said that after Egypt's Suez Canal, it was the most important passage for Britain to control in order to keep the Russians from advancing towards British India.
Mahan first used the term in his article "The Persian Gulf and International Relations", published in September 1902 in the National Review, a British journal. The Middle East, if I may adopt a term which I have not seen, will some day need its Malta, as well as its Gibraltar. Naval force has the quality of mobility; the British Navy should have the facility to concentrate in force if occasion arise, about Aden and the Persian Gulf. Mahan's article was reprinted in The Times and followed in October by a 20-article series entitled "The Middle Eastern Question," written by Sir Ignatius Valentine Chirol. During this series, Sir Ignatius expanded the definition of Middle East to include "those regions of Asia which extend to the borders of India or command the approaches to India." After the series ended in 1903, The Times removed quotation marks from subsequent uses of the term. Until World War II, it was customary to refer to areas centered around Turkey and the eastern shore of the Mediterranean as the "Near East", while the "Far East" centered on China, the Middle East meant the area from Mesopotamia to Burma, namely the area between the Near East and the Far East.
In the late 1930s, the British established the Middle East Command, based in Cairo, for its military forces in the region. After that time, the term "Middle East" gained broader usage in Europe and the United States, with the Middle East Institute founded in Washington, D. C. in 1946, among other usage. The description Middle has led to some confusion over changing definitions. Before the First World War, "Near East" was used in English to refer to the Balkans and the Ottoman Empire, while "Middle East" referred to Iran, the Caucasus, Central Asia, Turkestan. In contrast, "Far East" referred to the countries of East Asia With the disappearance of the Ottoman Empire in 1918, "Near East" fell out of common use in English, while "Middle East" came to be applied to the re-emerging countries of the Islamic world. However, the usage "Near East" was retained by a variety of academic disciplines, including archaeology and ancient history, where it describes an area identical to the term Middle East, not used by these disciplines.
The first official use of the term "Middle East" by the United States government was in the 1957 Eisenhower Doctrine, which pertained to the Suez Crisis. Secretary of State John Foster Dulles defined the Middle East as "the area lying between and including Libya on the west and Pakistan on the east and Iraq on the North and the Arabian peninsula to the south, plus the Sudan and Ethiopia." In 1958, the State Department explained that the terms "Near East" and "Middle East" were interchangeable, defined the region as including only Egypt, Israel, Jordan, Saudi Arabia, Kuwait and Qatar. The Associated Press Styleboo
In chemistry, an alcohol is any organic compound in which the hydroxyl functional group is bound to a carbon. The term alcohol referred to the primary alcohol ethanol, used as a drug and is the main alcohol present in alcoholic beverages. An important class of alcohols, of which methanol and ethanol are the simplest members, includes all compounds for which the general formula is CnH2n+1OH, it is these simple monoalcohols. The suffix -ol appears in the IUPAC chemical name of all substances where the hydroxyl group is the functional group with the highest priority; when a higher priority group is present in the compound, the prefix hydroxy- is used in its IUPAC name. The suffix -ol in non-IUPAC names typically indicates that the substance is an alcohol. However, many substances that contain hydroxyl functional groups have names which include neither the suffix -ol, nor the prefix hydroxy-. Alcohol distillation originated in India. During 2000 BCE, people of India used. Alcohol distillation was known to Islamic chemists as early as the eighth century.
The Arab chemist, al-Kindi, unambiguously described the distillation of wine in a treatise titled as "The Book of the chemistry of Perfume and Distillations". The Persian physician, alchemist and philosopher Rhazes is credited with the discovery of ethanol; the word "alcohol" is from a powder used as an eyeliner. Al- is the Arabic definite article, equivalent to the in English. Alcohol was used for the fine powder produced by the sublimation of the natural mineral stibnite to form antimony trisulfide Sb2S3, it was considered to be the essence or "spirit" of this mineral. It was used as an antiseptic and cosmetic; the meaning of alcohol was extended to distilled substances in general, narrowed to ethanol, when "spirits" was a synonym for hard liquor. Bartholomew Traheron, in his 1543 translation of John of Vigo, introduces the word as a term used by "barbarous" authors for "fine powder." Vigo wrote: "the barbarous auctours use alcohol, or alcofoll, for moost fine poudre."The 1657 Lexicon Chymicum, by William Johnson glosses the word as "antimonium sive stibium."
By extension, the word came to refer to any fluid obtained by distillation, including "alcohol of wine," the distilled essence of wine. Libavius in Alchymia refers to "vini alcohol vel vinum alcalisatum". Johnson glosses alcohol vini as "quando omnis superfluitas vini a vino separatur, ita ut accensum ardeat donec totum consumatur, nihilque fæcum aut phlegmatis in fundo remaneat." The word's meaning became restricted to "spirit of wine" in the 18th century and was extended to the class of substances so-called as "alcohols" in modern chemistry after 1850. The term ethanol was invented 1892, combining the word ethane with the "-ol" ending of "alcohol". IUPAC nomenclature is used in scientific publications and where precise identification of the substance is important in cases where the relative complexity of the molecule does not make such a systematic name unwieldy. In naming simple alcohols, the name of the alkane chain loses the terminal e and adds the suffix -ol, e.g. as in "ethanol" from the alkane chain name "ethane".
When necessary, the position of the hydroxyl group is indicated by a number between the alkane name and the -ol: propan-1-ol for CH3CH2CH2OH, propan-2-ol for CH3CHCH3. If a higher priority group is present the prefix hydroxy-is used, e.g. as in 1-hydroxy-2-propanone. In cases where the OH functional group is bonded to an sp2 carbon on an aromatic ring the molecule is known as a phenol, is named using the IUPAC rules for naming phenols. In other less formal contexts, an alcohol is called with the name of the corresponding alkyl group followed by the word "alcohol", e.g. methyl alcohol, ethyl alcohol. Propyl alcohol may be n-propyl alcohol or isopropyl alcohol, depending on whether the hydroxyl group is bonded to the end or middle carbon on the straight propane chain; as described under systematic naming, if another group on the molecule takes priority, the alcohol moiety is indicated using the "hydroxy-" prefix. Alcohols are classified into primary and tertiary, based upon the number of carbon atoms connected to the carbon atom that bears the hydroxyl functional group.
The primary alcohols have general formulas RCH2OH. The simplest primary alcohol is methanol, for which R=H, the next is ethanol, for which R=CH3, the methyl group. Secondary alcohols are those of the form RR'CHOH, the simplest of, 2-propanol. For the tertiary alcohols the general form is RR'R"COH; the simplest example is tert-butanol, for which each of R, R', R" is CH3. In these shorthands, R, R', R" represent substituents, alkyl or other attached organic groups. In archaic nomenclature, alcohols can be named as derivatives of methanol using "-carbinol" as the ending. For instance, 3COH can be named trimethylcarbinol. Alcohols have a long history of myriad uses. For simple mono-alcohols, the focus on this article, the following are most important industrial alcohols: methanol for the production of formaldehyde and as a fuel additive ethanol for alcoholic beverages, fuel additive, solvent 1-propanol, 1-butanol, isobutyl alcohol for use as a solvent a
The European roller is the only member of the roller family of birds to breed in Europe. Its overall range extends into Central Asia and Morocco; the European roller is found in a wide variety of habitats. It winters in dry wooded savanna and bushy plains, where it nests in tree holes; the rollers are medium-sized Old World birds of open woodland habitats. They have brightly coloured a hooked bill. Most are found south of the Sahara; the genus Coracias contains eight species of sit-and-wait hunters. The European roller is similar in appearance and behaviour to the Abyssinian roller, which appears to be its closest relative; these two birds and the lilac-breasted roller seem to share a common ancestry and could be considered to form a subspecies. The European roller was described by Linnaeus in his Systema naturae in 1758 under its current name; the genus name derives from Greek. The species garrulus means chattering or noisy. Alternate names include the blue roller, common roller, Eurasian roller, or roller.
There are two subspecies recognised: Western European roller - Linnaeus, 1758: The nominate subspecies. Found in north-western Africa and east through north-western Iran to south-western Siberia. Eastern European roller - Loudon & Tschusi, 1902: Also named the Kashmir roller. Found in Iraq and southern Iran east through Kashmir and southern Kazakhstan to Xinjiang in western China; the European roller is a stocky bird, the size of a jackdaw at 29–32 cm in length with a 52–58 cm wingspan. Rollers perch prominently on trees, posts or overhead wires, like giant shrikes, whilst watching for the large insects, small reptiles and frogs that they eat; this species is striking in its strong direct flight, with the brilliant blue contrasting with black flight feathers. Sexes are similar; the display of this bird is a lapwing-like display, with the twists and turns that give this species its English name. It nests in an unlined tree or cliff hole, lays up to six eggs; the call is a harsh crow-like sound. It gives a raucous series of calls when nervous.
The European roller is a bird of warmer regions. The nominate subspecies breeds in northern Africa from Morocco to Tunisia, in southern and east-central Europe, eastwards through northwestern Iran to southwestern Siberia; the subspecies C. g. semenowi breeds from Iraq and southern Iran east through Kashmir and southern Kazakhstan to Xinjiang. The European range was more extensive, but there has been a long-term decline in the north and west, with extinction as a nesting bird in Sweden and Germany; the European roller is a long-distance migrant, wintering in Sub-Saharan Africa in two distinct regions, from Senegal east to Cameroon and from Ethiopia west to Congo and south to South Africa. Some populations migrate to Africa through India. A collision with an aircraft over the Arabian Sea has been recorded, it is a bird of warm, open country with scattered trees, preferring lowlands, but occur up to 1000 m in Europe and 2000 m in Morocco. Oak and pine woodlands with open areas are prime breeding habitat, but farms and similar areas with mixed vegetation are used.
In Africa, a wide range of dry open land with trees is used. It winters in dry wooded savanna and bushy plains, where it nests in tree holes; the European Roller chick will vomit a foul-smelling orange liquid onto itself to deter a predator. The smell warns the parents on their return to the nest; the advent of sufficiently lightweight tracking technology has facilitated several recent studies of roller migration, providing new information on the non-breeding sites used by rollers from different breeding populations. Individuals from south-west European populations migrate to south-west Africa, with French and north-Spanish birds taking a direct southerly route across the Sahara and Portuguese and south-Spanish taking a more westerly route around the west African coast. Rollers from eastern European populations spend the winter period in southern Africa, but further east in Zambia, Botswana; the Sahel savannah region south of the Sahara Desert appears to be important for rollers from many populations as an autumn re-fuelling site, Latvian and other north and north-eastern populations migrate northwards via the Arabian Peninsula in spring.
Individuals from different breeding populations use overlapping winter sites. In the east, the northernmost breeders tend to winter south of the southernmost breeders - this suggests a pattern of'leap-frog' migration; the Eurasian roller has an extensive distribution in Europe and western Asia, its European breeding population is estimated at 159,000 to 330,000 birds. When Asian breeders are added, this gives a global total population of 277,000 to 660,000 individuals. There have been rapid population declines across much of its range, so it was classified as Near Threatened by the International Union for Conservation of Nature in 2005; the European population declined by 25 percent between 1990 and 2000. The northern areas of the breeding range have fared worst, with numbers in