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
Orbital node terms αναβιβάζων and καταβιβάζων were also used for the ascending and descending nodes, giving rise to the English words "anabibazon" and "catabibazon". For the orbit of the Moon around Earth, the plane is taken to be the ecliptic, not the equatorial plane. The gravitational pull of the Sun upon the Moon causes its nodes to gradually precess westward, completing a cycle in approximately 18.6 years. Orbital node An orbital node is either of the two points where an orbit intersects a plane of reference to which it is inclined. A non-inclined orbit, which is contained in the reference plane, has