Electricity of the Heart







                      
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             In the heart there is a small cluster of cells called the Sinoatrial Node or SA node. 
             From this spot the current of electricity is propogated that contracts the atria, or
             the top chambers of the heart and downward towards the next cluster of cells
             called the atrioventricular node or AV node.  The AV node sends an impulse down
             a bundle of nerves called the bundle of His.  This contracts the lower two chambers
             of the heart called the ventricles.  This whole phenomenon happens at a rate of roughly
             60-100 times per minutes  (pennard community first responders).  If you are to listen to
             a heartbeat, you would normally hear a lub dub type sound.  This first sound is the
             of the atrial chambers caused by the SA node firing.  The second sound, the dub, is caused
             by the AV node firing closing the ventricles.


            The nerves of the body, but esspecially in the heart, act a wires that deliver electricity.  When at rest
           Every cell in the heart has negative charge.  As we increase the negative charge up to zero, this is called
           depolarization.  To do this there is an influx of positivly charged Sodium and Calcium and Potassium ions into the cells.
           This causes the cells to contract as the electrical stimulous moved throughout the cells stimulating originally
           from the SA node.  In general a persons heartbeat generates 100 milivolts on every beat (discovery health).

 
           Due to the fact that the heart works off of electricity, we are able to restart, or reset a heart when the nodes dont work correctly
           or when both of them try to fire at the same time.  The device we use to do this is called and Automated External Defirilator, or AED.
           AEDs are essentially very small capacitors that are able to deliver a very large, short term shock to reset the rythm of the heart.


                        
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