The heartbeat originates in the:
A. sinoatrial node located at the junction of
the vena cava and the right atrium.
B. sinoatrial node located at the junction of
the vena cava and the left atrium.
C. atrioventricular node located in the wall of
the atrioventricular valve.
D. atrioventricular node located in the tissue
separating the atria and ventricles.
E. sinoatrial node and atrioventricular node
simultaneously.
A
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