(thing) by moses2 Fri Aug 10 2001 at 15:30:59

The sinus node, or sino-atrial node, is what makes your heart beat spontaneously. Its a region of highly specialized heart cells located in the wall of the vena cava superior, near the right atrium of the heart. The electrical activity of the human heart originates from there - and this creates the heartbeat. About 70 times every minute, your whole life through, without rest, night and day...

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