Electrical Conductivity of the Heart
Have you ever wondered just how important your heart is? Do you ever think about it to keep it beating? Well, the answer is probably no. Your heart is an amazing organ. It has the ability to function on its own. The heart is about the size of you fist lying in the middle of you chest. It is composed of numerous fibers and tissues, which allows it to operate and pump blood though out your body. The fibers allow electricity to be transmitted across the heart. The main areas that deal with the electrical impulses are the SA node, the AV node, the Bundle of His, and the purkinje fibers. Together, all these components contract the heart and pump blood through the body. The sinoatrial (SA) node, or the natural pacemaker of the heart, is where the electrical impulses are generated. It is located in the upper wall of the right atrium near the opening from the superior vena cava. The SA node sets the contraction rate by generating nerve impulse
The normal rate for the impulses to be generated is between sixty and eighty beats per minute. This process only takes seventy-five milliseconds! Ventricular contraction occurs, and blood is either pumped into the body or pumped towards the lungs. The purkinje fibers transmit the electrical signal very quickly. The whole process of atrial and ventricular contraction only takes about 225 milliseconds. From the SA node to the next receptor in the heart, it only takes fifty milliseconds for the signal to travel. It does not need an external stimuli for the production of the electrical impulses, it does this on its own. This process contracts both the atria and the ventricles simultaneously to sustain life. When the electrical signals reach the AV node from the SA node, the signal is delayed for one-tenth of a second to allow the atria to empty their contents of blood. The AV bundle or the bundle of His is the only electrical connection between the atria and the ventricles. The electrical impulses start in the SA node, travel down to the AV node, then travel to the bundle of His, and finally get transmitted to the purkinje fibers. This rate can increase when one is aroused, exercising, angry, or frightened and this rate can decrease when one is sleeping or hibernating. The signal travels across them as quickly as a signal travels in a myelinated nerve axon. It is located in the bottom of the right atrium in the interatrial septum. These fibers are set up so that the blood is aimed towards the openings of the aorta and the pulmonary arteries.
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