The heart's electrical system
The heart is a powerful muscle that rhythmically contracts. The activity of the heart is controlled by electrical signals (impulses). The conduction system of the heart (see illustration ) ensures that these impulses travel through the entire muscle. Normally, there is a small area in the right atrium, SA node (sinoatrial knutsen), which controls the electrical impulses. At rest, the SA node triggers approx. 60-70 per minute electrical impulses that spread out over the heart. From the SA node, impulse spreads itself first in the two atria. The impulse is then caught up in an area located at the transition between the atria and ventricles, AV node (AV node). From the AV node, the impulse is led through pipes located in the septum (septum) between the right and left ventricle. The first part of this cord is called the bundle; it splits as a right and a left branch line, and from these branches spreading as impulses in the muscles themselves respectively the right ventricle and left ventricle.
Heartbeat
A heartbeat consists of two contractions of the heart muscle. First pull the atria contract so that the blood in the atria is pushed down into the ventricles. Then pull the ventricle's contract. The heart valves close when the atria and prevent blood flow back to the atria, while opening the heart valves from the right and left ventricles so the blood can be pumped into the pulmonary circulation, respectively, and the wide circulation. It is the electrical impulses that control heart rate when the impulse from the SA node spreads out in the atria. When the impulse reaches the ventricular wall, pull the ventricular muscle together.
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