Heart rate date normally used to date pregnancy in the medical community. The electrical depolarizations that trigger cardiac myocytes to contract arise spontaneously within the myocyte itself. The heartbeat is initiated in the pacemaker regions and spreads to the rest of the heart through a conduction pathway. Pacemaker cells develop in the primitive atrium and the sinus venosus to form the sinoatrial node and the atrioventricular node respectively. Conductive cells develop the bundle of His and carry the depolarization into the lower heart. The human heart begins beating at a rate near the mother’s, about 75–80 beats per minute (bpm). The embryonic
Cardiac neural crest cells and GATA families of molecules. In addition to these signaling pathways, these processes are also mediated by environmental factors including blood flow, shear stress, and blood pressure. The CNCCs interact with the cardiogenic mesoderm cells of the primary and secondary heart fields, which are derived from the cardiac crescent and will give rise to the endocardium, myocardium, and epicardium. The CNCCs themselves are the precursors to vascular smooth muscle cells and cardiac neurons. For example, CNCCs are required for the formation of the aorticopulmonary septum (APS) that directs cardiac outflow into two tracts: the pulmonary trunk and the aorta of