What is the primary action associated with motilin?

Motilin is a peptide hormone that plays a crucial role in regulating gastrointestinal motility, particularly during the fasting state. Its primary action is the initiation of the migrating motor complex (MMC), which is a pattern of peristaltic movements that occur in the stomach and small intestine. This complex helps to clear out residual food particles and secretions from the digestive tract between meals, thus promoting gut motility and preventing the growth of bacteria in the small intestine.

The MMC is characterized by intermittent contractions that sweep from the stomach into the intestines, maintaining gastrointestinal hygiene and preparing the system for the next meal. Motilin levels rise during fasting and stimulate these contractions, contributing to the regulation of gut motility and facilitating the movement of contents through the digestive tract.

While gastric acid secretion, insulin secretion, and gallbladder contraction are important physiological processes, they are not primarily influenced by motilin. Gastric acid secretion is mainly mediated by other hormones such as gastrin, whereas insulin secretion is regulated by glucose levels and other factors. Gallbladder contraction is primarily stimulated by cholecystokinin in response to fatty meals. Therefore, the role of motilin as the initiator of the MMC distinctly highlights its central function in promoting gastrointestinal motility.