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
"What Is This Heart?" of 69, based on 32 reviews, which indicates "generally favorable reviews". Ian Cohen of Pitchfork Media gave a very positive review of the album stating, ""What Is This Heart?" makes you initially susceptible and vulnerable, and that’s risky when modern discourse seeks metaphorical blood, allowing people to disclose more than ever without actually revealing anything. So make no mistake, the title of this album is a challenge as well, as How to Dress Well’s modern masterpiece is conducted with the most eternal transparency—Krell asks “what is this heart” and lets you look right into his own." "What Is This Heart?"