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
Lunar node Lunar node A lunar node is either of the two orbital nodes of the Moon, that is, the two points at which the orbit of the Moon intersects the ecliptic. The "ascending" (or "north") node is where the Moon moves into the northern ecliptic hemisphere, while the "descending" (or "south") node is where the Moon enters the southern ecliptic hemisphere. A lunar eclipse can occur only when the full Moon is near (within 11° 38' ecliptic longitude) either lunar node, while a solar eclipse can occur only when the new Moon is near (within 17° 25') either lunar node. Because