Karel Frederik Wenckebach "second degree AV block" and later named the "Wenckebach phenomenon" and reclassified as Mobitz type I block in Mobitz's 1924 paper. A similar phenomenon can also occur in the Sinoatrial node where it gives rise to Type I second degree SA block, and this is also known as a Wenckebach block; the two have distinct features on an ECG however. Wenckebach is credited for describing the median bundle of the heart's conductive system that connects the sinoatrial node to the atrioventricular node. This bundle was named Wenckebach's bundle, and is also known as the middle internodal tract. Wenckebach's bundle is
Sinoatrial node it has arisen from the circumflex artery, which is a branch of the left coronary artery. Finally, the SA node artery commonly passes behind the superior vena cava, before reaching the SA node; however in some instances it passes in front. Despite these many differences, there doesn’t appear to be any advantage to how many sinoatrial nodal arteries an individual has, or where they originate There are no large veins that drain blood away from the SA node. Instead, smaller venules drain the blood directly into the right atrium. The main role of a sinoatrial node cell is to initiate