# Emesis --- **Emesis** or **vomiting** is the rapid expulsion of [[stomach|gastric]] contents. It is a complex reaction that can have many causes, but ultimately is triggered by the **vomiting center** of the [[medulla oblongata]] and often accompanied by a preceding feeling of [[nausea]]. Several types of receptors are involved in the vomiting response, especially [[serotonin]], [[dopamine]], [[acetylcholine]], and [[histamine]]. Once activated, the vomiting center signals the [[stomach]], [[diaphragm]] and abdominal muscle and results in a coordinated response which expels gastric contents. ## Risks Associated with Emesis One or two episodes of emesis can usually be tolerated without ill effects, but repeated, frequent emesis is cause for concern. The primary risk is to one's [[acid-base balance]]. This is because the loss of [[stomach acid|HCl]] necessities it's replacement, which releases [[bicarbonate]] (a base) into the blood stream. This can lead to [[alkalosis|metabolic alkalosis]]. >[!science] Acids and Bases are Zero Sum >When the body makes an acid, it also makes a base, and vice versa. It's a system. Other risks are a breakdown of the [[esophagus]] and mouth due to the acidic stomach acid, and an increased chance for aspirating the vomit into the lungs. ___