Nausea And Vomiting

Nausea is the body's way of teaching a person to avoid the substance or situation that caused it. Although nausea does nothing to remove toxins from the body, it leaves the person with a horrible memory which is apt to be attached to the last thing they ate. Another form of "deal with the stimuli causing you to feel this way."

There is no single accepted definition of nausea in medicine. So each person needs to come up with his or her own. For our purposes, nausea is a feeling in the stomach rhythm that all is not well. Specifically, it is caused by contractions contrary to the normal pattern of contractions within the stomach or perhaps the complete lack of contractions.

Ordinarily the immediate effect of nausea is to stop a person from eating or drinking further. Nausea may also include pallor, sweating, excessive salivation, and increased respiration.

The usual causes of nauseousness are viral illness, food or alcohol poisoning, bodily injury (particularly if the person can see the injury) unpleasant smells, emotional upset or anxiety, migraine headache, hunger, and medications.

Vomiting is the forceful expulsion of contents of the stomach and often, the proximal small intestine. It is a manifestation of a large number of conditions, many of which are not primary disorders of the gastrointestinal tract. Regardless of cause, vomiting can have serious consequences, including acid-base derangments, volume and electrolyte depletion, malnutrition and aspiration pneumonia. Poison or toxic material may get into the stomach from spoiled food, drinking poison or acid, drinking too much alcohol, allergic reaction, or through an illness.

If poisonous or harmful in your stomach, that material sends warning signals to your brain. The defense mechanism is to immediately eject that poisonous material from the body. This is done through the act of vomiting.

There are three phases to the vomiting act: nausea, retching, and expulsion. Vomiting is ordinarily preceded by nausea. It is not unheard of for a person to vomit without feeling nauseated, particularly in cases of sudden injury or sudden shock, such as witnessing an awful sight or breathing a particularly noxious smell. Vomiting that occurs suddenly and without warning is called precipitate vomiting. But most people experience nausea for a period of time before they vomit.

The stomach is relatively unimportant in the act of vomiting. The brain is in charge, and muscles adjacent to the stomach do the work. The vomiting center is located in the medulla oblongata, the rear part of the brain. This neural center acts on information supplied by the stomach, the intestines, the gag reflex in the throat, the inner ear, and most importantly, the chemoreceptor trigger zone (CTZ), which is located on the floor of the fourth ventricle in the brain, in case anyone cares. The CTZ takes in data about the presence of toxins in the blood and alerts the vomiting center to go to work when it believes the body has been poisoned. The stomach and intestines can signal for vomiting to occur when they are irritated or overloaded. The function of the gag reflex in the throat -- actually the province of something called the constrictor muscle -- is well known.

The second phase of the vomiting cycle is retching. The contractions of retching feel much like those of the expulsion phase, but retching too does not lead inevitably to vomiting. The vomiting cycle thus can be halted at any point prior to expulsion. In retching, the respiratory and abdominal muscles contract, forcing the gastric contents into the esophagus, but this is not enough to propel them out of the body. At the rest phases between retches, the stomach contents reflux back into the stomach.

The key distinction between retching and expulsion is the motion of the diaphragm. When vomiting occurs, it is because the diaphragm relaxed suddenly during the retching cycle, enabling the stomach contents to be expelled through the mouth.

The muscles that do the work are the diaphragm and the abdominal muscles. When the body is ready to vomit, the pyloric sphincter (which separates the stomach from the duodenum) closes, while about 45 seconds before vomiting, the lower esophageal sphincter (which separates the stomach from the esophagus) relaxes greatly, pulling the top of the stomach into the shape of an inverted funnel. The stomach contracts to shift contents from the lower to the upper portion. The abdominal muscles tighten, and the diaphragm goes down sharply in one or more contractions, squeezing the stomach. With the usual exit from the stomach closed, the contents have nowhere to go but up.

Content Of Vomit

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.

The content of the vomitus (vomit) may be of medical interest. Fresh blood in the vomit is termed hematemesis ("blood vomiting"). Old 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 become both extremely painful and debilitating.

All in all, vomiting is usually a beneficial process to help protect a person from serious injury or even death. The body reacts quickly and violently to rid the stomach of any harmful material. In some cases, like morning sickness, it is an unfortunate side effect that is not beneficial.