The human heart is a marvelous organ.
The function of the heart is to move the living stream of blood through all parts of the body, never stopping even for a moment in its endless activity. The heart is however, one single organ but it actually consist of two pumps – right and left.
The right side of the heart with its two chambers, receives blood from all parts of the body and propels it to the lungs. There the blood drops its load of carbon dioxide and receives a fresh supply of oxygen, then passes to the left side of the heart (with its two chambers also) and from there it is pumped to all parts of the body.
Each side of the heart operates independently of the other, but they act together in keeping the blood circulating normally. The walls of the heart consist of powerful muscle fibres that have the power to contract or beat rhythmically. This constant rhythmic beating keeps the circulation going.
How the heart beats
The motions of the heart are maintained by a specially designed structure Known as the sinoatrial node or SA node. This little structure is capable of initiating a regular rhythm, and transmitting these electrical impulses to all the muscle fibres of the heart wall. This is how the constant rhythmic contractions are maintained.
The SA node or pace maker is located near the top of the heart. It really operates like a small radio station, flashing out its signals in regular electric waves. These are the P waves seen on the electrocardiogram or tracing of the heart. These P waves make the atria or auricles (the left and right upper chambers) contract to fill the ventricles (the two lower chambers).
Lower, down near the main valves of the heart, another small structure, the atrioventricular or AV node, picks up these radio signals and transmits them through the special conduction fibres or filaments to all the muscle cells of the powerful ventricles or pumping chambers of the heart. These electrical impulses are the QRS waves seen on the electrocardiogram. Almost instantly after the QRS wave the ventricular walls contract, emptying the pumping chambers into the aorta and out into all the arteries. This is the pulse you can feel at your wrist.
Then for a split second the heart relaxes and fills with blood. It is now ready for the next contraction or beat. This whole amazing process is an engineering feat without any equal. Because of the simultaneous electric flash, all the heart muscle cells contract as one unit, even though they are each stimulated individually by these electrical impulses coming from above.
Endeavour to share this article for the purpose of education and knowledge.