Heart arrhythmia muscle cell firing off an impulse on its own. All of the cells in the heart have the ability to initiate an action potential; however, only some of these cells are designed to routinely trigger heart beats. These cells are found in the conduction system of the heart and include the SA node, AV node, Bundle of His and Purkinje fibers. The sinoatrial node is a single specialized location in the atrium that has a higher automaticity (a faster pacemaker) than the rest of the heart and, therefore, is usually responsible for setting the heart rate and initiating each heart
Heart rate the brake and let the engine increase speed. In the case of the heart, decreasing parasympathetic stimulation decreases the release of ACh, which allows HR to increase up to approximately 100 bpm. Any increases beyond this rate would require sympathetic stimulation. The cardiovascular centres receive input from a series of visceral receptors with impulses traveling through visceral sensory fibers within the vagus and sympathetic nerves via the cardiac plexus. Among these receptors are various proprioreceptors, baroreceptors, and chemoreceptors, plus stimuli from the limbic system which normally enable the precise regulation of heart function, via cardiac reflexes. Increased physical activity results