from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A small mass of specialized cardiac muscle fibers located in the posterior wall of the right atrium of the heart that acts as a pacemaker by generating at regular intervals the electric impulses of the heartbeat. Also called sinoauricular node, sinus node.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a specialized bit of heart tissue that controls the heartbeat
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