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Chapter 1 The Electrical Activity of the Heart. Basic concepts. The heart is a pump that sends blood to every organ in the human body. This is carried out through an electrical stimulus that originates in the sinus node and is transmit-ted through the specific conduction system (SCS) to contractile cells.
The mean QRS electrical axis is influenced by (a) the position of the heart in the chest, (b) the properties of the cardiac conduction system, and (c) the excitation and repolarization properties of the ventricular myocardium.
A thorough understanding of normal mechanisms of cardiac electrical activation and modifying factors is a necessary precursor to understanding disease states, and their appropriate treatment. General Outline. I. II. III. IV. V. Basic Electrophysiology. Membranes, ions, currents. Resting membrane potential.
CONDUCTION SYSTEM ANATOMY. The functions of the electrical system of the heart (Fig. II-1) are not only initiation and rate of the heartbeat, but its coordinated transmission to the entire heart resulting in maximum mechanical efficiency.
The Heart and Its Electrical System. The heart’s main job is to pump blood. The upper chambers (atria) take in blood from your lungs and body, and they pass that blood on to the lower chambers (ventricles) through your heart’s first set of valves. The second set of valves then open and your ventricles push your blood out to your lungs and body.
1.2 The Electrical Conduction System of the Heart Cardiac muscle is composed of two main cell types: cardiomyocytes, which gener-ate electrical potentials during contraction, and cells specialized in the generation and conductionof the action potentials. These specialized electrical cells depolarize spontaneously.
In the heart, the electrical changes needed to generate a cardiac impulse are regulated by its own conduction system, which starts with a sequence of excitation in a specialised area of cardiac cells, the sinoatrial node (SAN), situated in the right atrium. This is the heart’s natural pace-maker. When working properly, it sets the
