Final answer:
The sinoatrial node is known as the pacemaker of the heart, and the atrioventricular node has the slowest rate of firing in the heart conduction system. correct option is D.
Step-by-step explanation:
The Pacemaker of the Heart and Heart Conduction System
The component of the heart known as the pacemaker is the sinoatrial (SA) node, which is responsible for initiating the heart's electrical impulse and setting the pace for its rhythm. In the heart conduction system, the atrioventricular node has the slowest rate of firing when compared to other components such as the atrioventricular bundle, bundle branches, and Purkinje fibers.
The atrioventricular bundle, also known as the bundle of His, is a group of specialized myocardial conductile cells that transmit the impulse from the AV node through the interventricular septum and form the left and right atrioventricular bundle branches, which enable the transmission of electrical impulses to the ventricles for contraction.