The Cardiac Cycle

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Cardiac Cycle

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What is the cardiac cycle?
The contraction phase (systole) and the relaxation phase (diastole) of the cardiac muscle that occurs in one heart beat.
Describe step 1
The SA (Sinoatrial) node, located in the upper-right atrium, initiates the heartbeat.
Describe Step 2
The AV (atrioventricular) node, located in the lower interatrial septum, receives electrical impulses and both the right and left atria contact which forces to the ventricles
Describe Step 3
The impulse passes to the AV bundle that separates into the right and left bundle branches.
Describe Step 4
In the right and left bundle branches, the impulse travels to the Purkinje fibers covering the ventricles causing them to contract. The ventricles then force blood into the aorta and pulmonary artery. 
Describe Step 5
The Cycle Starts Again