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chapter 12: the cardiovascular system: the heart 12-2 (the conducting…
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nodal cells
nodal cells are unusual because their cell membranes depolarize spontaneously and generate action potentials at regular intervals.
nodal cells are electrically coupled to one another, to conducting cells, and to normal cardiac muscle cells.
as a result,when an action potential is initiated in a nodal cell, it sweeps through the conducting system, reaching all of the cardiac muscle tissue and causing a coordinated contraction
in this way, nodal cells, determine the heart rate
not all nodal cells depolarize at the same rate, and the normal rate of contraction is established by pacemaker cells, the nodal cells that reach threshold first
these pacemaker cells are located in the sinoatrial node( SA node), or cardiac pacemaker, a tissue mass embedded in the posterior wall of the right atrium near he entrance of the superior vena cava