Nervous Activities of the Heart in Crustacea

Findings show that the cardiac rhythm arises not only at the cardiac ganglion but also at certain neurons in the ganglions.

Abstract

Crustacean cardiac rhythms, unlike those of vertebrates, do not originate in the heart muscle itself. Ganglion cells are normally located in the dorsal wall of the heart and the excitation for the heart beat starts at the ganglion. A neurogenic origin of the heart beat, however, was first demonstrated in Limulus by Carlson (1904). He applied a warm test tube on various parts of the heart muscle and ganglion and found that the cardiac rhythm was accelerated only when the tube was placed on a certain part of the ganglion (the fourth and fifth segments of the ganglion). If the ganglion was removed from the heart the beat stopped. These findings show that the cardiac rhythm arises not only at the cardiac ganglion but also at certain neurons in the ganglion.