Cardiac cycle

The cardiac cycle is an ongoing sequence of contraction and relaxation of the atria and ventricles that keeps blood continuously circulating round the body. The volume of the atria and ventricles change as they contract and relax. Pressure changes also occur; due to the changes in chamber volume (e.g decreasing the volume of a chamber by contraction will increase the pressure of a chamber). The cardiac cycle can be simplified into three stages:

1.       Ventricles relax, atria contract

The ventricles are relaxed. The atria contract, decreasing the volume of the chamber and increasing the pressure inside. This pushes blood into the ventricles. There’s a slight increase in ventricular pressure and chamber volume as the ventricles receive the ejected…