Qualia

Have you ever asked yourself how the heart beats? You have probably heard that the heart has a pacemaker that regulates its rhythm, and this is indeed true. The chief pacemaker of the heart is the Sinoatrial node (SA node), located on the top right portion of the heart. It sends out a signal that descends down and to the left through nerve fibers that induce contraction of the heart in a coordinated fashion. The SA node has a natural rhythm but is also under the control of parasympathetic and sympathetic nerve fibers which can decrease and increase the heart rate, respectively.