Fig. 11. Neurophysiology of the digestive tract correlates of vomiting. There are 2 sensory pathways: (1) digestive tract mucosa sensing digestive tract contents with vagal afferents to the CNS and (2) the chemoreceptive trigger zone (CTZ) of the area postrema (AP) sensing blood borne agents with afferents to the central pattern generator (CPG). The AP serves multiple tasks. It not only mediates blood borne activation of the CPG, but it also transmits sensory signals from the nucleus tractus solitarius (NTS) to the CPG and inhibits dorsal vagal nucleus (DVN) mediated contraction of orthograde movement. The CPG controls the timing of the 3 basic digestive tract motor events of emesis. The first set of events is inhibition of lower esophageal sphincter (LES) and fundus which are probably controlled by the DVN, and activation of cricopharyngeus (CP) and thyropharyngeus (TP) which are probably controlled by the nucleus ambiguus (NA). The second set of responses is the retrograde giant contraction (RGC), but the CNS motor nucleus controlling this response is unknown. However, we do know that these outputs from this center are transmitted through the DVN to the vagus nerves, celiac ganglia, mesenteric ganglia, mesenteric nerves, to the intestine. The fibers then project distally 10 cm to 15 cm before innervating the intestinal musculature. The ENS is involved in this process but it is unknown at what stage of this process. The third set of responses during the retch and vomit are then activated by the CPG, but the subnucleus controlling these responses is unknown. It has been hypothesized that the respiratory movements of the retching and vomiting are controlled by the caudal portion of the ventral respiratory group (cVRG), but it is unkown what role this has in the digestive tract correlates of vomiting. Bot, Bötzinger nucleus; R&V, retch and vomit; UES, upper esophageal sphincter; ESOc, cervical esophagus; G, ganglia; N, nerve; ENS, enteric nervous system.
© J Neurogastroenterol Motil
