Gastrointestinal function peristalsis

Numerous in vitro and in vivo techniques have been employed for the study of cannahinoid agonists and antagonists on gastrointestinal functions. These include in vitro studies on isolated gastrointestinal muscle preparations, in vitro peristalsis studies, in vivo gastrointestinal motility studies, in vitro and in vivo... 

The intestines are suspended in a sheath of fascia known as the mesentery. In quadrupeds, the intestines float in the abdominal cavity in coils and the chyme moves through the lumen unimpeded by gravity. In humans, peristalsis must overcome gravity as well as tensions created by the layers of intestines in a fairly narrow space. In addition, medications and some foods can have the effect of altering gastrointestinal function. 

Figure 6.4 Types of intestinal motility patterns. Segmentation, tonic contraction, and peristalsis are the three major types of motility patterns observed in the gut. Each serves a specific function for digestion and processing of luminal contents. From E.B. Chang, M.D.Sitrin and D.D.Black (1996) Gastrointestinal motility and neurophysiology. Gastrointestinal, Hepatobiliary, and Nutritional Physiology, Lippincott-Raven, Philadelphia, pp. 27-51...

The peripheral effects concern the motility and tonus of gastrointestinal smooth muscle segmentation is enhanced but propulsive peristalsis is inhibited. The tonus of sphincter muscles is markedly raised (spastic constipation). The antidiarrhetic effect is used therapeutically (loperamide, p.180). Gastric emptying is delayed (pyloric spasm) and drainage of bile and pancreatic juice is impeded because the sphincter of Oddi contracts. Likewise, bladder function is affected specifically bladder emptying is impaired owing to an increased tone of the vesicular sphincter. 

Carminatives—serve to promote normal bowel function by stimulating peristalsis and relaxing the gastrointestinal tract. 

The autonomic system is responsible for the moment-to-moment modification of practically all functions of the body. Although there are intrinsic plexi that promote normal activity, the sympathetic and parasympathetic systems enhance or retard function. Auerbach s and Meissner s plexi become activated by intraluminal distension and initiate peristalsis in an anterograde fashion. Increased parasympathetic activity, primarily from the vagus nerve in the cranial axis, increases gastrointestinal motility. The same can occur from microbial and chemical irritation of the inner walls. The effects are decreased transit time and decreased water absorption, among other effects. The person may also have other symptoms including discomfort, nausea, oating, and irritation. 

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