The action potential is a sudden positive shift in the cardiomyocyte's cellular membrane potential, termed depolarization. Depolarization not only initiates contraction within the affected cardiomyocyte (Described in Cardiac Excitation-Contraction Coupling), but also initiates depolarization of adjacent cardiomyocytes.
Polar Coordinates The coordinate system which depicts the points from the pole to the certain distance at a particular angle is known as âpolar coordinatesâ. The positive horizontal axis in which that particular angle rotates is named as âpolar axisâ.
More About Cartesian Plane. 1  The location of any point on the coordinate plane is denoted by using pair of coordinates (X, Y), where X is the horizontal distance from the origin and Y is the vertical distance from the origin.  The X and Y-axis on the coordinate plane is always perpendicular to each other.