Fig. 3.

Signal propagation in a theoretical model. (A) Sketch of a tube and the concentration of a signaling molecule within the tube over time (color gradient, see legend of C). The signal increases the amplitude of radial contractions (smaller radius at high concentration) and so establishes a self-propagating front of increased signal concentration and contraction amplitude. When a region of large contraction amplitude contracts (between two white lines marking amplitude front location) surroundings expand, or vice versa. (B) Kymograph of tube radius along the tube over time. Amplitude front is marked by phase jump between stimulated region and surroundings (white line). (C) Map of the time-averaged signal concentration; spread is caused by flow. The location of the front as measured by the position of the phase jump coincides with the mean averaged concentration across the tube at every time point (white line).