... Activators of Emesis Chapter 039. Nausea, Vomiting, and Indigestion (Part 1) Harrison's Internal Medicine > Chapter 39. Nausea, Vomiting, and Indigestion Nausea, Vomiting, and Indigestion: ... Optimal pharmacologic management of vomiting requires understanding of these pathways. Several brain stem nuclei—including the nucleus tractus solitarius, dorsal vagal and phrenic nuclei, medullary ... NK1, serotonin 5-HT3, and vasopressin pathways are postulated. Somatic and visceral muscles exhibit stereotypic responses during emesis. Inspiratory thoracic and abdominal wall muscles...