Discuss the pathophysiology of nausea and vomiting, including specific precipitating factors and/or diseases
Vomiting is the expelling of ingested food through the mouth. The medical term for vomiting is emesis. While nausea is not vomiting but the sensation to vomit.
Nausea and vomiting are often associated with many disease conditions. There are many diseases that induce vomiting. Chronic vomiting would lead to dehydration.
Antiemetic drugs are used to prevent vomiting. Examples of antiemetic drugs include rolapitant, dexamethasone, granisetron, etc.
In the brain, there are centers to control vomiting and nausea. Once the signal that induces vomiting reaches the vomiting centers of the brain, the brain sends a stimulus to vomit.
The vomiting center in the brain is present in the medulla oblongata. It can be activated in multiple ways. It can be directly activated by the irritants that cause vomiting, or through signals from various parts of the body such as the gastrointestinal tract, cerebral cortex, chemoreceptor trigger zones, thalamus, or vestibular region.
- In the gastrointestinal (GI) tract, when the serotonin binds to the 5HT3 receptors, it sends signals to the vomiting center through afferent fibers of cranial nerve IX.
- In the vestibular region when histamine and acetylcholine bind to H1 receptors, the signals are sent to the vomiting center of the brain.
- When certain drugs bind to the kappa receptors present in the chemoreceptor trigger zone, the signals are sent to the vomiting centers of the brain.
After receiving the signals from different regions, the vomiting center process and send a vomiting reflex to the GI tract.
- The reflex induces reverse peristalsis from the ilium, which pushes food from the small intestine towards the mouth.
- The diaphragm and the stomach contract and the oesophageal sphincter relaxes, allowing the movement of food from the intestine to the mouth through the stomach.
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