SAKnoten

SAKnoten, short for Sinoatrialknoten, is the natural pacemaker of the heart in German medical terminology. It refers to the sinoatrial node, a small cluster of specialized pacemaker cells located in the wall of the right atrium near the opening of the superior vena cava. The SAKnoten initiates electrical impulses that set the heart’s rhythm and rate.

Function and propagation: The SAKnoten generates spontaneous action potentials with an intrinsic rate typically around 60 to 100 beats per minute in healthy adults. These impulses spread through the atrial myocardium via gap junctions and internodal pathways to reach the atrioventricular (AV) node, then through the His-Purkinje system to coordinate heart contractions. The P wave on an electrocardiogram reflects atrial depolarization driven by the SAKnoten’s activity.

Regulation: The pace of the SAKnoten is modulated by the autonomic nervous system. Sympathetic stimulation increases the slope of the pacemaker potential, raising heart rate, while parasympathetic (vagal) input slows it down.

Clinical notes: SA node dysfunction, or sick sinus syndrome, can cause bradycardia, dizziness, or fainting if the node fails to generate adequate impulses. In some cases, secondary pacemakers (e.g., AV node) take over at slower rates. Abnormalities are evaluated with ECG and Holter monitoring; treatment may involve addressing underlying factors or, in some cases, electronic pacemaker implantation.

History: The pacemaking role of the SAKnoten was established in the early 20th century by researchers such as Keith and Flack (1906), who identified it as the heart’s primary pacemaker.