Cardiac pacemaker 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 for blood pumping, are called pacemaker cells, and they directly control the heart rate. They make up the cardiac pacemaker, that is, the natural pacemaker of the heart. In most humans, the concentration of pacemaker cells in the sinoatrial (SA) node is the natural pacemaker, and the resultant rhythm is a
Common name objects, typically an incomplete and informal classification, in which some names are degenerate examples in that they are unique and lack reference to any other name, as is the case with say, "ginkgo", "okapi", and "ratel". Folk taxonomy, which is a classification of objects using common names, has no formal rules and need not be consistent or logical in its assignment of names, so that say, not all flies are called flies (for example Braulidae, the so-called "bee lice") and not every animal called a fly is indeed a fly (such as dragonflies and mayflies). In contrast, scientific or biological