The rhythmic or wavelike contractions of the smooth muscle tissues in the digestive system. Peristalsis begins in the esophagus as food is swallowed and continues through the intestinal tract, culminating in defecation (bowel movement). Peristaltic movements differ in the various parts of the digestive system. in the esophagus they are strong, frequent waves that forcefully push food into the stomach. Esophageal peristalsis is so forceful, in fact, that it can push food into the stomach against the force of gravity. The walls of the stomach contract in different directions simultaneously to provide a churning action that mixes food with the stomach acids that begin the digestive process.
In the small intestine, peristalsis changes to more of a back-and-forth agitation, somewhat like the motion of a washing machine, that further “mashes” food with digestive enzymes and also moves the mixture, called a bolus, through the 20 to 22 feet of small intestine where the majority of digestion takes place. contractions occur every few seconds to minutes, depending on the intestinal contents. When the bolus reaches the large intestine it has become compact, and there is less of it to move. Peristalsis slows to a contraction every 20 to 30 minutes, inching the bolus through the six or so feet of large intestine to the rectum, where, when the rectum fills, a final strong contraction expels the fecal matter through the anus.
Parkinson’s disease slows peristalsis somewhat, as the involvement of motor function structures in the brain has an effect on certain smooth muscle action. anti-parkinson’s medications, particularly anticholinergic medications taken to relieve tremors, further slow peristalsis. These medications act on smooth muscle fibers in the digestive and urinary systems, slowing them significantly. A number of medical conditions, including diabetes, also adversely affect peristalsis. slowed peristalsis has several adverse effects for the person with Parkinson’s:
• It slows gastric motility, the rate at which food leaves the stomach. This slowing influences the effectiveness of Levodopa, which must be absorbed through the small intestine. The longer the levodopa remains in the stomach, the less of it is available for absorption. This is particularly a concern later in the course of the disease when levodopa efficacy becomes critical.
• it decreases appetite, as food remains in the digestive system longer. This causes the person to eat less or to eat less frequently; nutritional deficiencies may result.
• it interferes with digestion and the absorption of nutrients, further contributing to nutritional deficiencies.
• It causes constipation, an accumulation of unexpelled fecal matter, which is uncomfortable at the least and can result in intestinal blockages that require medical intervention.
Eating enough foods that are high in fiber (fresh fruits and vegetables, whole grains and whole grain products) and drinking plenty of water are the two most effective ways to maintain optimal intestinal function. sometimes it is necessary to adjust medication dosages, particularly of anticholinergics that directly affect intestinal function. Regular physical activity, especially walking, also helps to keep the digestive tract as active as possible. Many of the medications to combat slowed peristalsis, including metoclopramide (Reglan) and cisapride (Propul-sid), are apt to worsen the motor symptoms of Parkinson’s.
