sinussõlmest

The sinussõlmest, also known as the sinoatrial node (SA node), is a specialized group of cells in the right atrium of the heart. It is the primary pacemaker of the heart, responsible for initiating the electrical impulse that causes the heart to contract. The SA node generates electrical impulses at a regular rate, typically between 60 and 100 beats per minute in a healthy adult at rest.

The electrical impulse generated by the SA node spreads through the atria, causing them to contract and pump blood into the ventricles. The impulse then reaches the atrioventricular node (AV node), where it is briefly delayed before being transmitted to the ventricles. This delay allows the atria to fully contract before the ventricles begin to contract. The impulse then travels through the ventricles, causing them to contract and pump blood to the rest of the body.

The rate at which the SA node fires can be influenced by various factors, including the autonomic nervous system. The sympathetic nervous system can increase the heart rate, while the parasympathetic nervous system can decrease it. Hormones, such as adrenaline, can also affect the SA node's firing rate.

Disruptions in the function of the SA node can lead to various heart rhythm disorders, known as arrhythmias. These can include bradycardia (a slow heart rate) or tachycardia (a fast heart rate), as well as irregular heart rhythms. Conditions affecting the SA node are often diagnosed through electrocardiogram (ECG) monitoring. Treatment depends on the specific condition and may involve medications or, in some cases, the implantation of a pacemaker to regulate the heart rhythm.