Final answer:
The motility of the GI tract is regulated by the autonomic nervous system and hormones. Sympathetic activation decreases motility, while parasympathetic activation increases motility. Hormones like motilin and gastrin also influence GI motility.
Step-by-step explanation:
The motility of the gastrointestinal (GI) tract is mainly regulated by two mechanisms: the autonomic nervous system and hormonal control.
The autonomic nervous system, which consists of the sympathetic and parasympathetic nerves, controls GI motility. Sympathetic activation decreases GI secretion and motility, whereas parasympathetic activation increases GI secretion and motility. For example, during the fight-or-flight response, sympathetic activation restricts enteric neurons' activity, leading to decreased motility. In contrast, during the rest-and-digest response, parasympathetic activation stimulates enteric neurons and increases GI motility.
Hormonal control also plays a role in regulating GI motility. Hormones like motilin and gastrin influence the contractile movements of the GI tract, leading to peristalsis and the movement of chyme through the intestines. For instance, motilin, released by the duodenal mucosa, initiates peristalsis in the form of migrating motility complexes, which propel chyme through the small intestine.