24.1 : 嘔吐の病態生理学

Vomiting, or emesis, is a protective reflex that forcefully expels stomach content due to triggers like medication, pregnancy, GI disorders or infections, or migraine.

In the brainstem, the vomiting center integrates signals from multiple sources, including the chemoreceptor trigger zone or CTZ, solitary tract nucleus or STN, vestibular apparatus, cerebral cortex, and GI afferent nerves.

The CTZ, rich in dopamine and opioid receptors, detects stimuli like cytotoxic drugs or opioids in the blood or cerebrospinal fluid, initiating vomiting.

The inner ear's vestibular apparatus sends signals to the CTZ via cranial nerve VIII, causing motion sickness.

In the GI tract, vagal and spinal afferent nerves contain serotonin receptors. Upon detecting pathogens or toxins, GI mucosa releases serotonin. This activates afferent nerves, transmitting signals through the CTZ or STN, ultimately stimulating the vomiting center.

Lastly, the cerebral cortex can trigger vomiting in response to unpleasant sights, foul smells, or anticipatory stress.