What is the SA Node?

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  • Written By: Meshell Powell
  • Edited By: Melissa Wiley
  • Last Modified Date: 15 November 2019
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The SA node is a bundle of nerve tissue found in the human heart. This tissue acts as a natural pacemaker and is called by other names as well. Some other words for this node include sinoatrial node, sinus node, or SAN. This node works by generating nerve impulses at regular intervals, thus causing the heart to beat at the same intervals. In a healthy heart, this interval is between 60 and 70 beats per minute when the heart is at rest.

When the SA node sends out electrical impulses, a series of electrical events are triggered in the heart. These events are responsible for the muscle contractions, which work to pump the blood from the heart to the rest of the body. Therefore, this node is a crucial part of the nervous system as well as the circulatory system.

Along with the other components of the electrical system of the heart, the SA node produces voltage changes within the heart. These voltage changes can be measured by placing electrodes on the skin and performing a test known as an electrocardiogram, often referred to as an ECG. This test is beneficial in detecting abnormalities in electrical activity, often helping to diagnose and treat problems before they become life-threatening.


Normally, nerve cells need some sort of external stimulus in order to fire, or send out electrical impulses. This is not the case with the SA node, as it has the capacity to fire on its own. This ability contributes to the reasons the SA node is often referred to as the primary pacemaker of the heart. If, for some reason, the SA node becomes damaged or otherwise stops functioning properly, there are other cells in the heart that will begin to take over the pacemaker role.

There are a number of medical conditions that can cause the sinus node to stop functioning normally, including diabetes or any condition affecting the heart. While many patients will not experience any negative side effects at all, others may experience a variety of unpleasant side effects. Some of these symptoms include heart palpitations, chest pain or discomfort, or difficulty breathing. In some cases, cardiac arrest may occur.

An ECG can often detect minor problems before something as severe as cardiac arrest occurs. Therefore, it is important to take any unusual symptoms seriously. Prompt medical attention is crucial to the health and well-being of the patient.


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Post 1

Can a-fib? be caused by some external events that cause tachycardia?

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