Sinoatrial node is influenced by nerves that supply it. The sinoatrial node is a banana-shaped structure that varies in size, usually between 10-30 millimeters (mm) long, 5–7 mm wide, and 1–2 mm deep. The SA node is located in the wall (myocardium) of the right atrium, laterally to the entrance of the superior vena cava in a region called the sinus venarum (hence "sino-" + "atrial)". It is positioned roughly between a groove called the crista terminalis located on the internal surface of the heart and the corresponding sulcus terminalis, on the external surface. These grooves run between the entrance of the
Longitude of the ascending node Longitude of the ascending node The longitude of the ascending node (☊ or Ω) is one of the orbital elements used to specify the orbit of an object in space. It is the angle from a reference direction, called the "origin of longitude", to the direction of the ascending node, measured in a reference plane. The ascending node is the point where the orbit of the object passes through the plane of reference, as seen in the adjacent image. Commonly used reference planes and origins of longitude include: In the case of a binary star known only from visual observations,