The atrioventricular node ( lat. Nodus atrioventricularis , atrial chamber node '), in short: AV node or Aschoff-Tawara node (after Ludwig Aschoff and the Japanese pathologist Sunao Tawara ), lies in the Koch triangle and belongs to the excitation conduction system of the Heart . It consists of specialized heart muscle cells and is located in the wall between the right and left atrium on the border with the heart chambers. The AV node continues into the bundle of His , which in turn divides into the two tawara limbs .
The excitation emanating from the sinus node is passed on via the working muscles of the atria. Since these are electrically isolated from the chambers by the connective tissue of the heart , the excitation cannot spread to the muscles of the chambers.
The AV node represents the only electrical connection between the atria and ventricles and has by far the lowest conduction velocity of the heart at 0.04–0.1 m / s. The excitation is transmitted to the chambers with a long delay. This delay, which corresponds to the PQ time in the ECG , is of great importance for the coordinated contraction of the atrial and ventricular muscles: After the atria have contracted ( diastole of the ventricle), the ventricles contract ( systole ) only after some time, which contributes to an improved chamber filling.
If the sinus node fails , the AV node takes over its function, albeit with a significantly lower frequency of 40–50 min −1 . The AV node also has the ability to spontaneously electrical depolarization , which, however, normally does not come into play, since the sinus node “forces” its higher frequency onto the AV node.
If the electrical conduction in the AV node is too slow or blocked, it is called an AV block . An accelerated transition between the atrium and ventricles, bypassing the AV node, occurs, for example, in Wolff-Parkinson-White syndrome .