Physiological Mechanisms of Vomiting

Neural Control and Afferent Pathways

The vomiting center receives input from four primary sources, including the chemoreceptor trigger zone, gastrointestinal tract, pharynx, and cerebral cortex, which detect various stimuli such as toxins, mucosal irritation, and psychological triggers 1, 2, 3
The chemoreceptor trigger zone in the area postrema detects circulating toxins, drugs, and metabolites in the blood, triggering the emetic response 1, 2
The gastrointestinal tract via vagal afferent fibers responds to mucosal irritation, distension, or inflammation, contributing to the vomiting reflex 1, 3

Multiple neurotransmitter receptors, including serotonin (5-HT3) and dopamine receptors, are involved in the emetic response, with primary and secondary receptors playing a role in the vomiting center and gastrointestinal tract 1, 2, 4
Activation of these receptors by chemotherapeutic agents, toxins, or their metabolites triggers the emetic cascade, which can be blocked by antiemetic agents 1, 2, 4
Efferent impulses from the vomiting center are transmitted to the salivation center, abdominal muscles, respiratory center, and cranial nerves, producing increased saliva, forceful abdominal muscle contractions, and coordinated respiratory and pharyngeal responses 1, 2, 3

Nausea and vomiting are related but may occur via different mechanisms, with nausea being a subjective sensation involving the cerebral cortex and more difficult to control than vomiting itself 4
Patients receiving effective antiemetic regimens often experience more nausea than vomiting, with younger patients and women being particularly susceptible 4