Peripheral Nervous Pathways Involved in Nausea and Vomiting

Abstract

During nausea and vomiting, a complex sequence of autonomic and somatic phenomena is observed: changes in respiratory rhythm and depth, increase in salivation, licking and deglutition, gastric relaxation and duodenal-pyloric spasm, contractions of the respiratory muscles and changes in heart rate and blood pressure. The activation of the efferent neurons initiating these events is co-ordinated by the vomiting centre located in the medulla oblongata, in the floor of the fourth ventricle. The vomiting centre receives input from the cerebral cortex, the vestibular organs, the chemoreceptor trigger zone (CTZ) and from afferent fibres coming from the periphery, including the gastrointestinal system. We will discuss the peripheral afferent and efferent nervous pathways involved in nausea and vomiting, focusing our attention on the nervous pathways to and from the gastrointestinal system. As it has been suggested that dopamine plays a role in the pathways controlling the gastric relaxation which occurs during nausea, this will be discussed in more detail. For further information and references about the subject discussed, the reader is referred to the general literature list given at the end of this chapter. Within the text references are cited only for some particular experimental observations.