Anatomy and Physiology of the Heart - Part 6

Blood flow in the heart is done by the contraction of the heart muscle.

The cardiac cycle is divided into two periods:

1. Diastole - The ventricle muscle is relaxed.
2. Systole - The ventricle muscle is contracted.

Both sides of the heart work in coordination: contract and relax almost simultaneously (the left ventricle, with thicker muscle, actually precedes by a fraction of a second (20-30ms)). The same volume of blood flows to both sides with every beat.

Wiggers Diagram:

A Wiggers diagram beautifully illustrates events and details of the cardiac cycle with electrographic (ECG) trace lines as well as heart sounds:

(Below is a great gif of the heart contracting with a Wiggers diagram timeline).