Figure 1.

The crustacean cardiac system and experimental procedure for characterizing the NMT. A, Schematic diagram of the intact crustacean cardiac system. The cardiac CPG (green box) sends feed-forward neural commands to the cardiac tissue, which provides feedback to the cardiac ganglion. The cardiac ganglion consists of four premotor neurons (in blue) and five motor neurons (in red), all of which are spontaneously oscillatory. B, In stimulated heart preparations, the cardiac CPG is removed (top) and the motor nerve is electrically stimulated by a suction electrode (bottom). C, Example trace from a stimulated heart preparation. The schematic on the left illustrates a more realistic representation of the crustacean heart than the diagrams in A and B. The cardiac motor nerve is stimulated (red trace), and muscle movement (black trace) is recorded via a force transducer.