<unk> <unk>  EC<unk>  describes the series of events, from the production of an electrical impulse (action potential) to the<unk>  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<unk>  results in the sequential<unk>  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 body is at rest. This rate can be altered, however, by nerves that work to either increase heart rate (sympathetic nerves) or decrease it (parasympathetic nerves), as the body's oxygen demands change. Ultimately, muscle<unk>  revolves around a charged atom (ion), calcium (Ca2+), which is responsible for converting the electrical energy of the action potential into mechanical energy<unk>  of the muscle. This is achieved in a region of the muscle cell, called the transverse-tubule during a process known as calcium induced calcium release.
Cardiac excitation-contraction coupling
Myocardial contractility
Myogenic tone
Cardiac rhythmicity
Skeletal-muscle pump
Electrical conduction system of the heart
Vagal tone
Cardiac cycle