Sinoatrial node action potentials, so that it can pass throughout the heart and cause contraction. An action potential is a change in voltage (membrane potential) across the membrane of the cell, produced by the movement of charged atoms (ions). Non-pacemaker cells (including the ventricular and atrial cells) have a period, immediately after an action potential, where the membrane potential remains relatively constant; this is known as a resting membrane potential. This resting phase (see cardiac action potential, phase 4) ends when another action potential reaches the cell. This produces a positive change in membrane potential (known as depolarisation), which initiates the start
Orbital node moves south through the plane. In the case of objects outside the Solar System, the ascending node is the node where the orbiting secondary passes away from the observer, and the descending node is the node where it moves towards the observer. The position of the node may be used as one of a set of parameters, called "orbital elements", which describe the orbit. This is done by specifying the longitude of the ascending node (or, sometimes, the longitude of the node.) The line of nodes is the intersection of the object's orbital plane with the plane of reference. It