Luminal Chemoreceptors and Intrinsic Nerves: Key Modulators of Digestive Motor Function

This chapter reviews data on the pathways by which luminal, mainly duodenal, chemoreceptors modulate gastro-pyloro-duodenal motor function to control emptying of nutrients into the small intestine. The vagus mediates proximal gastric relaxation caused by nutrient stimulation of duodenal/jejunal mucosal chemoreceptors. Modulation of the spatial patterning and inhibition of antral contractions during duodenal chemoreceptor activation are somewhat conflicting: both vagal control and ascending intramural nerves appear to play a role. Intraduodenal nutrients stimulate the localized pyloric contractions that prevent transpyloric flow via ascending duodenal intramural nerve pathways. Though not yet formally investigated, patterns of activation of the duodenal brake motor mechanism suggest that duodenal loop mucosal chemoreceptors signal to a brake mechanism at the most aborad region of the duodenum via descending intramural duodenal nerves. Intrinsic intramural pathways are important in the control of the first stages of digestion.

Automated summary

This chapter examines the role of luminal chemoreceptors in modulating gastro-pyloro-duodenal motor function, particularly in controlling the emptying of nutrients into the small intestine. The vagus nerve and intramural nerves are both involved in controlling gastric relaxation and antral contractions during duodenal chemoreceptor activation. In addition, localized pyloric contractions prevent the flow of nutrients through the pylorus, mediated by ascending duodenal intramural nerve pathways. The duodenal brake motor mechanism is likely signaled by descending intramural duodenal nerves. The intrinsic intramural pathways play a crucial role in the early stages of digestion.