Question

What is the significance of atrio-ventricular node and atrio-ventricular bundle in the functioning of heart?

Answer 1

Hint: The heart is one of the most important organs and involved in the pumping of blood to different parts of the body. It is a muscular organ and by rhythmic movements pumps blood to transport respiratory gases such as oxygen and carbon dioxide as well as certain chemicals such as hormones and enzymes. In humans and other mammals, the heart is divided into four chambers which ensures movement of blood in a circulation as well as prevents backflow.

Complete answer: The heart remains enclosed in a pericardium or the protective sac. It consists of four chambers in mammals, which are upper and lower atria and lower left and right ventricles. The right atrium and the lower right ventricle are together known as the right heart and the opposite atrium and ventricle of the left side is known as the left heart. The pumping action of the blood by the heart takes place in a rhythmic manner and it is determined by the action of several cells known as the pacemaker cells and are found in the sinoatrial node. The sinoatrial node causes contraction of the heart by generating signals. The generation of signals by the sinoatrial node forms the electrical conduction system of the heart.
The sinoatrial node (SA) along with the atrioventricular node, Bundle of His, Purkinje fibers and atrioventricular bundle generates the rhythmic contraction of heart and leads to the movement of blood. The SA node which is located in the right atrium stimulates the contraction of the atria. The impulse then passes to the atrioventricular node (AV node).
 The AV node is found in the interatrial septum and it conducts impulse from the atria to the ventricles. The contraction and retraction of the heart is brought about by the depolarization and repolarization which is caused by movement of ions across the cell membranes. The Av node after receiving the impulse delays it and the impulse passes through the Bundle of His to reach the Purkinje fibers of both sides and finally reaches the ventricular portion of the heart.
The atrio-ventricular bundle is also known as Bundle of His is a continued part of the specialized tissue present in the AV node. It serves to transmit the impulse from the AV node to the Purkinje fibers. The atrio-ventricular bundle then divides into two branches which are the right bundle branch and the left bundle branch. The right bundle branch conducts the impulse to the right ventricle and the left branch conducts to the left ventricle.

Note: The contraction of the heart is brought about by the impulse passed on from the sinoatrial node to the atrioventricular node and further to the atrioventricular bundle. The AV node is responsible for conduction of impulse to the bundle and it also protects the ventricle by delaying the impulse for a few seconds. This prevents the blood from quickly moving into the ventricle. The atrioventricular bundle moves the nerve impulse to the Purkinje fibers and finally to the ventricles. It is referred to as the pacemaker system of the heart.