Ask A Scientist Molecular Biology Archive

name         sarah josephine uribe
status       student
age          12

Question -   What group of cells that adjusts the speed of heart beat?
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The pace maker cells do it but any cardiac muscle cell can do it if the
pacemaker cells fail to do their job. 

PF
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There is a patch of cells in the upper right atrium called the sinoatrial node.  They "fire" an 
action potential (bit of electricity) at a slightly faster rate than the rest of the cells around 
them.  This is why it is sometimes called the "pacemaker" of the heart, because it sets the pace of 
the heartbeat.  This wave of electricity then spreads from one cell to another throughout the atria 
(left and right) then passes to another bunch of cells called the AV or atrioventricular node.  The 
atria then contract.  Once the blood passes from the atria to the ventricles the wave of electricity 
passes to the venticular cells and they contract forcing the blood out of the heart.
 
vanhoeck
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