Fig. 1. Myogenic motor patterns in animals.

The images show graphical representations of wall motion captured by video recordings of a colon segment in an organ bath. Each frame of the video is converted to a greyscale image that maps changes in colon diameter. In these diameter maps (DMaps), darker shading represents an increased diameter (dilation) and lighter regions represent a reduced diameter (contraction). The three DMaps show the three main myogenic (non-neurogenic) patterns of motor activity in the colon of different animal species (in vitro isolated preparations). a | In the colon of most experimental animals, chaotic shallow contractions, termed ripples, are generated by a network of pacemaker cells at the submucous border (interstitial cells of Cajal (ICC) submucosal) acting on the circular muscle to elicit slow waves. In this example from a rabbit distal colon, these ripples become prominent once the neural activity is blocked by tetrodotoxin²⁰. b | In some species, faster ripples have been recorded, which seem to be generated by a net of pacemaker cells located at the myenteric plexus level (ICC myenteric). In this example from the rabbit proximal colon, fast phasic contractions appear following application of hexamethonium, which blocks nicotinic receptors²⁴. c | Slow phasic contractions have been recorded, for example in the rat colon after blocking neural activity with lidocaine and then applying the cholinergic agonist carbachol; whether these slow myogenic contractions exist in all species remains to be determined³⁷. Part a adapted with permission from ref.²⁰, The American Physiological Society. Part b adapted from ref.²⁴, Springer Nature Limited. Part c adapted from ref.³⁷, CC-BY-4.0 https://creativecommons.org/licenses/by/4.0/.