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What is the chemoreceptor trigger zone?

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Quick Answer

The chemoreceptor trigger zone is a set of neurons in the brainstem underneath the floor of the fourth ventricle. The chemoreceptor trigger zone senses chemical abnormalities in the body, generally from chemotherapy drugs or other illness within the body, and sends a signal to the vomiting center to trigger vomiting. In many cases, vomiting is caused by diseases that occur outside the gastrointestinal tract.

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Chemical abnormalities that are sensed by the chemoreceptor trigger zone include excess urea in the blood during kidney failure, excess ketones in the blood during diabetic ketoacidosis and lack of oxygen in the blood.

Electrical stimulation of the chemoreceptor zone does not induce vomiting. However, drugs that have emetic effects, such as those used in cancer treatments, can trigger the chemoreceptor trigger zone to send signals to the vomiting center, thus inducing vomiting. Anti-emetic drugs, or drugs that inhibit vomiting, act on the chemoreceptor trigger zone to prevent these signals.

Signals from other centers in the brain that are triggered by fear, odors and motion sickness can also trigger vomiting. In addition, signals from the gastrointestinal tract, bile duct and even the heart can also trigger the vomiting center.

Simple vomiting by itself is not usually cause for concern, but extended vomiting is an indicator of something more serious should be checked out by a physician.

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