The heart is composed of several varieties of cardiac muscle tissue. The atrial myocardium and ventricular myocardium, so named for their location, are similar structurally, although the electrical properties of these two areas differ significantly. The conducting tissues (e.g., Purkinje fibers) of the heart have a communicating function similar to nerve tissue, but they actually consist of muscle tissue that is highly adapted for the rapid and efficient conduction of action potentials, and their contractile ability is greatly reduced. Finally, there are the highly specialized tissues of the sinoatrial and atrioventricular nodes, muscle tissue that is greatly modified into structures concerned with the initiation and conduction of the heartbeat. The discussions that follow refer primarily to the ventricular myocardium, the tissue that makes up the greatest bulk of the muscle of the heart.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.