Adsorption: The adhesion of molecules to a surface. For example, bismuth salicylate coats the walls of the GI tract and binds the causative bacteria or toxin for elimination from the GI tract through the stool.

Antacids: Used to neutralize stomach acid and reduce the symptoms of heartburn.

Antidiarrheals: Relieve the symptoms of diarrhea, such as an increased frequency and urgency when passing stools, but do not eliminate the cause of it.

Antimotility medications: Medications that help to treat diarrhea by slowing peristalsis.

Area postrema: A structure in the medulla oblongata in the brainstem that controls vomiting. Its location in the brain also allows it to play a vital role in the control of autonomic functions by the central nervous system.

Chemoreceptor trigger zone (CTZ): Area in the brain that responds directly to toxins in the bloodstream and also receives stimuli from several other locations in the body that stimulate the vomiting center.

Cytochrome P-450 enzymes: Enzymes produced from the cytochrome P450 genes involved in the formation (synthesis) and breakdown (metabolism) of various molecules, chemicals, and medications within cells.

Defecation: The digestive process where undigested materials are removed from the body as feces.

Diarrhea: The passage of three or more loose or liquid stools per day (or more frequent passage than is normal for the individual).

Gastroenteritis: Infection of the intestines.

Gastroesophageal reflux disease (GERD): Caused by excessive hydrochloric acid that tends to back up, or reflux, into the lower esophagus.

Hematemesis: Blood in the vomit.

Hypercalcemia: Elevated levels of calcium in the bloodstream.

Intrinsic factor: Necessary for the absorption of vitamin B12 in the small intestine.

Osmotic agents: Cause water to be retained with the stool, increasing the number of bowel movements and softening the stool so it is easier to pass.

Parietal cells: Cells in the gastric glands that produce and secrete hydrochloric acid (HCl) and intrinsic factor.

Pepsin: A digestive enzyme.

Peptic ulcer disease (PUD): Occurs when gastric or duodenal ulcers are caused by the breakdown of GI mucosa by pepsin in combination with the caustic effects of hydrochloric acid.

Probiotics: Used for the prevention and treatment of diarrhea by restoring normal bacteria flora in the gastrointestinal tract.

Prokinetic: Medications used to promote peristalsis to empty the gastrointestinal tract and reduce nausea.

Proton pump inhibitors (PPIs): Bind to the hydrogen-potassium ATPase enzyme system of the parietal cell and inhibit the release of hydrogen ions into the stomach.

Rebound hyperacidity: A side effect of medication causing elevated levels of hydrochloric acid in the stomach after the medication is discontinued.

Serotonin syndrome: Symptoms associated with serotonin syndrome may include the following: mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, with or without gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea).

Stimulants: Laxatives that cause the intestines to contract, inducing stool to move through the colon.

Stool softeners: Laxatives that facilitate movement of water and fats into stool to make it soft and improve regularity of bowel movements.

Stress-related mucosal damage: A common condition in hospitalized patients that can lead to PUD.

Stress ulcer prophylaxis: Medication to prevent the formation of stress ulcers.

Surface epithelium cells: Cells found within the lining of the stomach that secrete mucus as a protective coating.

THC: Tetrahydrocannabinoids found in marijuana.

Vestibular system: An area located within the inner ear that gives a sense of balance and spatial orientation for the purpose of coordinating movement with balance. 

Vomiting center (VC): An area in the brain that initiates vomiting by inhibiting peristalsis and producing retro-peristaltic contractions beginning in the small bowel and ascending into the stomach. It also produces simultaneous contractions in the abdominal muscles and diaphragm that generate high pressures to propel the stomach contents upwards.