sinusknútur

The sinusknútur, also known as the sinoatrial node or SA node, is a specialized group of cells located in the upper right chamber of the heart, the right atrium. It is the natural pacemaker of the heart, responsible for initiating and regulating the heart's rhythm. The cells within the sinusknútur possess a unique property of automaticity, meaning they can spontaneously generate electrical impulses without external stimulation.

These electrical impulses originate in the sinusknútur and spread through the atria, causing them to contract. The impulse then travels to the atrioventricular node (AV node), where it is briefly delayed before being conducted to the ventricles, causing them to contract and pump blood to the rest of the body. The rate at which the sinusknútur generates these impulses determines the heart rate. Factors such as exercise, stress, and certain medications can influence the speed at which the sinusknútur fires, thereby altering the heart rate.

Disruptions to the normal functioning of the sinusknútur can lead to various heart rhythm disorders, collectively known as sinus node dysfunction. These can include a heart rate that is too slow (bradycardia), too fast (tachycardia), or irregular. Symptoms of sinus node dysfunction can vary but may include dizziness, fainting, shortness of breath, and fatigue. Diagnosis often involves an electrocardiogram (ECG) to assess the heart's electrical activity. Treatment depends on the specific dysfunction and may involve medication or the implantation of a pacemaker to regulate the heart rhythm.