Cardiac pacemaker ventricles, within the atrial septum. If the AV node also fails, Purkinje fibers are occasionally capable of acting as the default or "escape" pacemaker. The reason Purkinje cells do not normally control the heart rate is that they generate action potentials at a lower frequency than the AV or SA nodes. Cardiac pacemaker The contraction of cardiac muscle (heart muscle) in all animals is initiated by electrical impulses known as action potentials. The rate at which these impulses fire controls the rate of cardiac contraction, that is, the heart rate. The cells that create these rhythmic impulses, setting the pace
Cardiac excitation-contraction coupling Cardiac excitation-contraction coupling Cardiac excitation-contraction coupling (Cardiac EC coupling) describes the series of events, from the production of an electrical impulse (action potential) to the contraction of muscles in the heart. This process is of vital importance as it allows for the heart to beat in a controlled manner, without the need for conscious input. EC coupling results in the sequential contraction of the heart muscles that allows blood to be pumped, first to the lungs (pulmonary circulation) and then around the rest of the body (systemic circulation) at a rate between 60 and 100 beats every minute, when the