Siinussõlme

Siinussõlme, also known as the sinus node, is a natural pacemaker of the heart, located in the right atrium. It is a cluster of specialized cells that generate electrical impulses, which trigger the heart's contraction. The sinus node is the primary pacemaker of the heart, initiating each heartbeat. It is responsible for setting the heart rate, which is typically between 60 and 100 beats per minute in adults. The sinus node is self-regulating, adjusting the heart rate in response to changes in the body's needs, such as during physical activity or emotional stress.

The sinus node is composed of myocytes, which are heart muscle cells, and specialized cells called pacemaker cells. These pacemaker cells generate the electrical impulses that travel through the heart's conduction system, causing the heart to beat. The electrical impulses travel through the atrioventricular node, bundle of His, and Purkinje fibers, ensuring coordinated contraction of the heart's chambers.

The sinus node can be affected by various factors, including age, medications, and underlying medical conditions. As people age, the sinus node may become less efficient, leading to a slower heart rate. Certain medications, such as beta-blockers, can also slow the heart rate by inhibiting the sinus node's activity. Conditions like hyperthyroidism can increase the heart rate by stimulating the sinus node, while conditions like hypothyroidism can slow it down.

In some cases, the sinus node may fail to function properly, leading to conditions such as sinus node dysfunction or sick sinus syndrome. In these cases, a pacemaker may be necessary to maintain a regular heart rhythm. Understanding the role of the sinus node is crucial for diagnosing and treating heart rhythm disorders.