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Cardiovascular System I: The Beating Heart
Concept 1: Heart Anatomy
   Practice (2 pages)
   Review (4 pages)
Concept 2: The Cardiac Cycle
   Practice (1 page)
   Review (1 page)
Concept 3: Electrical Activity of the Heart
   Practice (2 pages)
   Review (2 pages)
Concept 4: Heart Pump Operation
   Practice (1 page)
   Review (1 page)
Concept 3: Electrical Activity of the Heart
The heart's rhythm of contraction is controlled by the sinoatrial node (SA node), often called the pacemaker. This node is part of the heart's intrinsic conduction system, which is made up of specialized myocardial cells called nodal cells.
• The heart will beat without input from the nervous system and will continue to beat, even outside the body, as long as its cells are alive.
• The automatic nature of the heartbeat is referred to as automaticity.
• Automaticity is due to the spontaneous electrical activity of the SA node. Electrical impulses generated from the SA node spread through the heart via a nodal tissue pathway that coordinates the events of the cardiac cycle.