Figure 2. Response of an isolated segment of duodenum to increasing intraluminal pressure induced by saline.

A shows a pressure recording taken as the intraluminal pressure was increased in 1 cmH₂O steps (arrows) from 2 cmH₂O (the basal level) to 6 cmH₂O. The second step triggered a single phasic contraction, while the third triggered a burst of contractions that did not continue though the stimulus was sustained. The last step triggered a series of contractions that continued until the infusion pressure was returned to baseline. The left panel of B shows the spatiotemporal map derived from video images corresponding to the pressure trace in A. The two right hand panels show the diameters at the same point tracked along the short dashed lines, with the circles indicating dilatations that preceded the contractions. C tracks the diameter of the duodenum at another point (long dashed line) showing both the phasic and tonic contractions.