Slow waves (electrophysiology)

At rest, smooth muscle cells, heart muscle or skeletal muscle , due to the gradient of ion concentration on both sides of the cell membrane, have a resting resting membrane potential.

Slow waves do not cause muscle contraction. The contraction of smooth muscle tissue occurs only when slow waves of fast electrical vibrations - action potentials (another name for action potentials - adhesions ) appear on the plateau. Slow waves create a potential in the muscles close to the activation threshold, which allows the emergence of action potentials with subsequent contraction of muscle fiber. With a high depolarization of the cell membrane, the action potentials can be initiated by a slow wave; with a low depolarization, the action potentials decay. The action potential causes a contraction of the organ wall and increases intraluminal pressure in the organ. Abbreviations can be segmental (non-propagating) and propulsive (propagating).

The rhythm of slow waves is set by special pacemakers , in which the interstitial cells of Cahal play the most important role. ^[one]

Parameters of slow waves in the body are stable. They do not change under the influence of acetylcholine , histamine , adrenaline , atropine , procaine , morphine , cocaine , despite the fact that all of these substances affect the occurrence of action potentials and smooth muscle contraction.

Slow waves play a crucial role in the motor activity of the organs of the gastrointestinal tract (GIT). Different sections of the gastrointestinal tract: the cardial section of the stomach, the body of the stomach, the antrum, the pyloric canal, duodenum, jejunum , ileum , various sections of the colon are independent motor complexes, the activity of which is coordinated through nerve and humoral mechanisms. Frequency and other characteristics of slow waves are different in different sections of the gastrointestinal tract. Slow waves propagate along the stomach and intestines in the caudal direction (from the entrance to the organ to the exit).

The membrane potential of leiomyocytes (cells that make up smooth muscle tissue) of the stomach is 55–70 mV. The average frequency of slow waves in the stomach is 2.88 ± 0.88 cycles per minute, the amplitude is 30–40 mV, the duration is 7.2–8.3 s, and the propagation speed is 5–6 mm per second. All these values ​​have a small scatter for different departments and different layers of the muscles of the stomach. ^[2]

Slow waves in the duodenum have a frequency of 10-12 cycles per minute, in the jejunum - 9-12 cycles per minute, in the ileum - 6-8 cycles per minute, in the colon there are waves with frequencies of about 0.6 ^[3] , as well as 3-12 cycles per minute ^[4] .

The exact location of the location of the pacemakers in the above sections of the digestive tract is unknown. It is believed that the pacemaker of the stomach is in the proximal (closest to the esophagus ) part of the stomach, and the pacemaker of the small intestine is probably in the area where the common bile duct enters the duodenum. However, when a portion of the stomach or intestines is removed, a pacemaker always appears, being a pacemaker for the lower parts of the organ.

Although the slow waves themselves are not the cause of contractions, the relationship between the characteristics of slow waves and the features of motor activity of various parts of the gastrointestinal tract is proved. Slow waves, in contrast to action potentials, can be detected from the surface of the patient’s body by a non-invasive device similar to an electrocardiograph . Such a diagnostic method is called electrogastrography (if only the stomach is examined) or electrogastroenterography (if the intestine is also examined), sometimes with the adjective “peripheral”, emphasizing that we are talking about recording electrogastro (entero) grams from the surface of the body, rather than implanted electrodes. The method is used in the diagnosis of postoperative complications, gastroparesis , adhesive intestinal obstruction, mesenteric thrombosis, gastric stenosis, infiltrative cancer of the stomach , ischemic bowel disease and other pathologies. ^[5]

• Migratory motor complex

• Ponomareva A.P., Rachkova N.S., Khavkin A.I., Belmer S.V. Diagnostic possibilities of electrogastroenterography in children with various gastrointestinal diseases . Materials of the XIII Congress of Pediatric Gastroenterologists of Russia. All-Russian meeting "Actual problems of abdominal pathology in children." Moscow, March 21-23, 2006.
• The official website of the Research Institute of Gastroenterology, Siberian State Medical University. Functional diagnostics .