Cardiac myocytes are the main heart tissue in the human body, which consists of cell divisions called cardiac muscle cells, or myocytes. Myocytes are the functional unit of the heart muscle and consist of so-called cardiomyocytes. These cells are found in the interventricular septum, right ventricle, atria and left ventricle. Myocytes are able to contract and relax under the influence of nerve impulses from the atria or ventricles. An electrocardiogram, also known as an ECG, is a simple way of obtaining information about the electrical activity of the heart. This is usually used to diagnose arrhythmia.