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Vomiting (also called throwing up or emesis) is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting may result from many causes, ranging from gastritis or poisoning to brain tumors, or elevated intracranial pressure (ICP). The feeling that one is about to vomit is called nausea. It usually precedes, but does not always lead to vomiting. Antiemetics are sometimes necessary to suppress nausea and vomiting, and, in severe cases where dehydration develops, intravenous fluid may need to be administered to replace fluid volume. The medical branch investigating vomiting, emetics and antiemetics is called emetology.
Vomiting is coordinated in the vomiting center in the lateral medullary reticular formation in the pons. Receptors on the floor of the fourth ventricle of the brain represent a chemoreceptor trigger zone, stimulation of which can lead to vomiting. The chemoreceptor zone lies outside the blood-brain barrier, and can therefore be stimulated by blood-borne drugs that can stimulate vomiting, or inhibit it.
There are various sources of input to the vomiting center:
The vomiting act encompasses three types of outputs initiated by the medulla: Motor, parasympathetic nervous system (PNS), and sympathetic nervous system (SNS). They are as follows:
The neurotransmitters that regulate vomiting are poorly understood, but inhibitors of dopamine, histamine, and serotonin are all used to suppress vomiting, suggesting that these play a role in the initiation or maintenance of a vomiting cycle. Vasopressin and neurokinin may also participate.
Since the stomach secretes acid, vomit contains a high concentration of hydronium ions and is, thus, strongly acidic. Recent food intake will be reflected in the gastric vomit. Irrespective of the content, vomit tends to be malodorous.
The content of the vomitus (vomit) may be of medical interest. Fresh blood in the vomit is termed hematemesis ("blood vomiting"). Altered blood bears resemblance to coffee grounds (as the iron in the blood is oxidized), and, when this matter is identified, the term "coffee ground vomiting" is used. Bile can enter the vomit during subsequent heaves due to duodenal contraction if the vomiting is severe. Fecal vomiting is often a consequence of intestinal obstruction, and is treated as a warning sign of this potentially serious problem ("signum mali ominis"); such vomiting is sometimes called "miserere."
If the vomiting reflex continues for an extended period of time with no appreciable vomitus, the condition is known as non-productive emesis or dry heaves, which can be painful and debilitating.
Aspiration of vomit
Vomiting can be very dangerous if the gastric content gets into the respiratory tract. Under normal circumstances the gag reflex and coughing will prevent this from occurring, however these protective reflexes are compromised in persons under narcotic influences such as alcohol or anesthesia. The individual may choke and asphyxiate or suffer an aspiration pneumonia.
Dehydration and electrolyte imbalance
Prolonged and excessive vomiting will deplete the body of water (dehydration) and may alter the electrolyte status. The loss of acids leads to metabolic alkalosis (increased blood pH), and the electrolyte imbalance shows hypokalemia (potassium depletion) and hypochloremia (chlorine depletion). The hypokalemia is an indirect result of the kidney compensating for the loss of acid. With the loss of intake of food the individual will become cachectic.
Repeated or profuse vomiting may cause erosions to the esophagus or small tears in the esophageal mucosa (Mallory-Weiss tear). This may become apparent if fresh blood is admixed with vomit after several episodes.
Recurrent vomiting, such as observed in bulimia nervosa, may lead to destruction of the tooth enamel due to the acidity of the vomit.
Vomiting may be due to a large number of causes, and protracted vomiting has a long differential diagnosis.
Causes in the digestive tract:
Sensory system and brain
Causes in the sensory system:
Causes in the brain:
Metabolic disturbances (these may irritate both the stomach and the parts of the brain that coordinate vomiting):
Drug reaction (vomiting may occur as an acute somatic response to):
An emetic, such as Syrup of Ipecac, is a substance that induces vomiting when administered orally or by injection. An emetic is used medically where a substance has been ingested and must be expelled from the body immediately. Inducing vomiting can remove the substance before it is absorbed into the body. Ipecac abuse can lead to detrimental health effects.
An antiemetic is a drug that is effective against vomiting and nausea. Antiemetics are typically used to treat motion sickness and the side-effects of some opioid analgesics and chemotherapy directed against cancer.
Antiemetics act by inhibiting the receptor sites associated with emesis. Hence, anticholinergics, antihistamines, dopamine antagonists, serotonin antagonists, and cannabinoids are used as anti-emetics.
Nausea inducement in groups
It is quite common that, when one person vomits, others nearby will become nauseated, particularly when smelling the vomit of others, often to the point of vomiting themselves. It is believed that this is an evolved trait among primates. Many primates in the wild will tend to browse for food in small groups. Should one member of the party react adversely to some ingested food, it may be advantageous (in a survival sense) for other members of the party also to vomit. This tendency in human populations has been observed at drinking parties, where excessive consumption of alcoholic beverages may result in a number of party members vomiting nearly simultaneously, this being triggered by the initial vomiting of a single member of the party. This phenomenon has been touched on in popular culture: Notorious instances appear in the films Monty Python's The Meaning of Life (1983) and Stand By Me (1986), while, in the computer game Theme Hospital, it is referred to as a 'vomit wave' and can spread through the hospital quickly.
Intense vomiting in ayahuasca ceremonies is a common phenomenon. However, people who experience "la purga" after drinking ayahuasca, in general, regard the practice as both a physical and spiritual cleanse and often come to welcome it.  It has been suggested that the consistent emetic effects of ayahuasca — in addition to its many other therapeutic properties — was of medicinal benefit to indigenous peoples of the Amazon, in helping to clear parasites from the gastrointestinal system. 
There have also been documented cases of a single ill and vomiting individual inadvertently causing others to vomit, when they are especially fearful of also becoming ill, through a form of mass hysteria.
Most people try to contain their vomit by vomiting into a sink, toilet, or trash can, as both the act and the vomit itself are widely considered embarrassing; vomit is also difficult to clean. On airplanes and boats, special bags are supplied for sick passengers to vomit into. A special disposable bag containing absorbent material that solidifies the vomit quickly is available, also, making it convenient and safe to keep (leakproof, puncture-resistant, odorless) until there is an opportunity to dispose of it conveniently.
People that vomit chronically (e.g., as part of an eating disorder such as bulimia nervosa) may devise various ways to hide this disorder.
According to an online study of 30 traditionally bad sounds, the sound of vomiting is the worst sound in the world. Professor Cox of the University of Salford's Acoustic Research Centre said that "We are pre-programmed to be repulsed by horrible things such as vomiting, as it is fundamental to staying alive to avoid nasty stuff". It is thought that the thought of disgust is triggered by the sound of vomiting to protect food from those possibly diseased nearby.
As with other physiological processes involving body wastes, vomiting has taboo aspects. This is shown by the large number of colourful euphemisms and dysphemisms for vomiting. (see: toilet humour). Reference to vomiting is often made in speech (e.g., "it makes me sick," "I need a bucket") or by gesturing to signify being disgusted by someone or something.
Slang terms for the act of vomiting include: "to hurl," "to throw up," "to gack," "to upchuck," "to boot," "to puke," "to ralph," "to call Earl," "to barf," "to keel," "to sick up," "to spew," "to spew chunks," "to chunder," "to toss one's cookies," "technicolor yawn," "street pizza," "to shout groceries," "to boke," and "to blow chunks"
"Wallace and Gromit" has recently become Cockney rhyming slang for vomit.
"Puke" and "puking" date from at least the 16th century. In As You Like It, Shakespeare talks of the infant 'Mewling and puking in the nurse's arms'.
Vomit phobia, or emetophobia, as it is also known, is the sixth-most-common phobia in the world, according to the International Emetophobia Society. In addition to the actual phobia, there are many other disorders and phobias that sufferers may be afflicted with, such as IBS and agoraphobia. People with emetophobia tend to avoid eating in public, socialising, and going to parties. They may hardly eat at all, and for this reason may be diagnosed as anorexic. Emetophobes will go to extraordinary lengths to avoid vomiting or seeing someone vomit. Some emetophobics have the distinct ability to actually prevent themselves from vomiting, called "vomit continence." They are able to fight the feeling of nausea before the feeling eventually subsides.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Vomiting". A list of authors is available in Wikipedia.|