The heart has a natural pacemaker: a set of cells whose electrical impulses trigger the heart's chambers to contract rhythmically. The stomach and intestine also have a pacemaker, but until recently no one knew where it lay. Now a team of researchers at McMaster University in Hamilton, Ontario, have pinpointed its location. A group of star-shaped cells that underlie the gut muscles generate gentle waves of excitation that control the rate at which the muscles contract and relax, moving food through the intestine.
Without a pacemaker, says physiologist Jan Huizinga, "gut muscles would generate contractions in a haphazard manner, and they could very easily go into a tonic contraction," a tight spasm from which they would be unable to relax. The pacemaker cells prevent that.
Researchers have suspected for some time that these cells--called the interstitial cells of Cajal--form the gut's pacemaker, but until Huizinga's work no one had been ...
