Electrical activity

Changes in the electrical potential of the smooth muscle coat are often used to assess gastrointestinal motility. Two types of electrical activity have been recorded in the colon i) slow wave activity and ii) spike potentials. The former consist of regular phasic depolarisations of the cell membrane which originate in the circular muscle layer of the transverse colon14. When compared with that of the stomach and small intestine, colonic slow wave activity is of low frequency and irregular. The slow wave pacemaker in the proximal or transverse colon maintains co-ordinated regular activity throughout the colon, and appears, at least in the cat, to migrate towards the caecum15 16. The retrograde propagation of slow waves in the proximal segment allows longer mucosal exposure for the intraluminal contents resulting in more complete absorption17. In man, the dominant slow wave frequency is 11 cycles per minute in the transverse and descending colon, slightly less in the caecum, ascending and sigmoid colon, whilst that in the rectum is the highest observed in the gastrointestinal tract at 17 cycles per min.

Spike potentials may be superimposed on the slow waves or may exist as bursts unrelated to slow wave activity, and are thought to initiate functional colonic contractions. Spike bursts of long duration (>10s) increase after eating and may increase luminal transit. Short duration spike bursts (<3.5s) are seen in patients with constipation and are not associated with movement of the intestinal contents. Such contractions only occur when the membrane potential rises above a prevailing threshold level which is set by both neural and humoral mechanisms.

Was this article helpful?

0 0
Constipation Prescription

Constipation Prescription

Did you ever think feeling angry and irritable could be a symptom of constipation? A horrible fullness and pressing sharp pains against the bladders can’t help but affect your mood. Sometimes you just want everyone to leave you alone and sleep to escape the pain. It is virtually impossible to be constipated and keep a sunny disposition. Follow the steps in this guide to alleviate constipation and lead a happier healthy life.

Get My Free Ebook


Post a comment