Monday, June 9, 2008

Heart Rate Control

Atrial Contraction
Atrial contraction is the broad term for when the atria of the heart contract. This is regulated by the SA Node.
SA Node
The SA Node, or the Sinoatrial node, is a tissue that instigates the left and right atrium to contract by generating electrical impulses. The SA node is located along the right atrium of the heart. The tissue forces a contraction 60 to 100 times a minute.
Ventricular Contraction
Ventricular contraction is the broad term for when the ventricles of the heart are forced to contract. This comes after the atrial contraction.
AV Node
The AV Node, or the Atrioventricular node, is an area of tissue that delays ventricle contraction. It is located between the atria and ventricles of the heart. After a short delay from the atria contraction, the AV node instigates two bundle branches (Bundle of His) to contract the left and right ventricles.
Purkinje Fibers
The two bundle branches (Bundle of His) branch off into the Purkinje Fibers. These fibers spread across the bottom portion of the heart, instigating the heart’s “big” contraction. On an ECG, the biggest wave is caused by the Purkinje Fibers.

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