Heart rate persons with coronary artery disease. The heart rate is rhythmically generated by the sinoatrial node. It is also influenced by central factors through sympathetic and parasympathetic nerves. Nervous influence over the heartrate is centralized within the two paired cardiovascular centres of the medulla oblongata. The cardioaccelerator regions stimulate activity via sympathetic stimulation of the cardioaccelerator nerves, and the cardioinhibitory centers decrease heart activity via parasympathetic stimulation as one component of the vagus nerve. During rest, both centers provide slight stimulation to the heart, contributing to autonomic tone. This is a similar concept to tone in skeletal muscles. Normally, vagal stimulation
Heart rate turbulence and activate the baroreflex in reverse. This time, the brain reinstates parasympathetic nerve signals and decreases sympathetic nerve signals, which cause the heart rate to slow (the turbulence slope part of HRT). The exact quantitative contribution of the parasympathetic and sympathetic nervous flow to the heart to HRT is unknown. The simplistic view assumes that HRT is solely dependent upon parasympathetic activity because atropine, a parasympathetic activity blocker abolishes HRT while a beta-blocker (sympathetic blocker) has no effect on HRT. The contribution of the compensatory pause, the pause between the PVC and the next normal beat, to HRT is also