The heart muscle pumps blood in our body without a break. A human heart is similar to a machine that continuously works to keep all the organs in the body working. The heart contracts and relaxes, triggering the whole process of blood circulation. Each contraction occurs at a set time and is triggered by an electrical impulse. These electrical impulses are controlled by a group of cells called the nodes. These nodes are the SA node and AV node. When these nodes weaken, it leads to many heart diseases that affect blood circulation.
As mentioned above, both these nodes are a group of specialized cells, each with a different function. The following paragraphs will discuss these nodes in detail and help you understand the difference between the two.
The sinoatrial (SA) node is the impulse generating tissue, in simple words, a pacemaker. It is located on the wall of the right atrium, near the entry point of superior vena cava. It triggers the electrical impulses that are carried around to other heart cells. The electrical impulses cause the atria to contract at the rate of 60 to 100 beats per minute. The dysfunction will cause irregular heart beats, where the heart rhythm become too fast, too slow, or occur in combination.
The atrioventricular (AV) node is a part of the electrical control system of the heart. It helps in coordinating the heart rate. The location is between the atria and the ventricles, in the interatrial septum of the heart near the opening of coronary sinus. The location is at the center of Koch's Triangle. This triangle consists of the tricuspid valve, coronary sinus, and the interatrial septum.
The function begins when it gets an electrical impulse from the SA node, which reaches the AV node first. The rhythm of heart contractions is set by the AV node. It delays the impulse by about 0.12 seconds. This delay is very important as it helps the atria eject blood into the ventricles before the contraction occurs. The delay also helps in protecting the ventricles from atrial arrhythmia (type of arrhythmia). The contraction rate is about 40 to 60 times per minute. Dysfunction includes many heart disorders such as, atrioventricular conduction disease and atrioventricular nodal re-entry tachycardia.
Some of the differences are enlisted in the following table for better understanding.
|Difference||SA Node||AV Node|
|Location||The location is in the right atrium, near the opening of superior vena cava.||The location is between the atria and heart ventricles, near the opening of the coronary sinus.|
|Stimulation||It is stimulated by the cardiac centers of the medulla oblongata.||It is stimulated by the cardiac impulses initiated by the SA node.|
|Function||The function is to initiate and maintain cardiac rhythm. It is therefore called the pacemaker of the heart.||The function is to set the rhythm of your heart contractions.|
Atrial fibrillation causes problems with the heart's electrical system. This means, the electrical impulses are not just generated in the SA node, but in different areas as well. This causes a high pulse rate and the right atrium fails to pump blood into the ventricle at the right time. Therefore, surgery is needed and an artificial pacemaker is attached in the heart to help stabilize the electrical impulses.
Disclaimer: This Buzzle article is for informative purposes only, and should not be used as a replacement for expert medical advice.