The regulation of gastrointestinal motility and secretion

Discuss the physiological mechanisms underlying the regulation of gastrointestinal motility and secretion, including the roles of smooth muscle contraction, neural reflexes, and hormonal factors such as gastrin and motilin. How do rhythmic contractions of smooth muscle in the gastrointestinal tract, coordinated by enteric nervous system reflexes and pacemaker cells like the interstitial cells of Cajal, propel ingested food through the digestive system via peristalsis and segmentation? Additionally, how do neural inputs from the autonomic nervous system and parasympathetic activation stimulate gastrointestinal motility and secretion in response to food ingestion and digestive cues? Furthermore, how do gastrointestinal hormones like gastrin, secretin, and motilin regulate gastric acid secretion, pancreatic enzyme release, and intestinal motility to facilitate digestion and nutrient absorption?