The pumping action of the healthy heart is triggered by electrical signals sent across the heart muscles. The electrical signal starts in the sino-atrial node, spreading to the atrio-ventricular node and down through the bundle of His to the right and left bundle branches and the purkinje fibres.
- Superior vena cava
The superior vena cava is the large vein which returns blood to the heart from the head, neck and both upper limbs. - Mitral valve
The mitral valve is composed of two triangular flaps. It is located between the left atrium and left ventricle and regulates blood flow between these chambers - Purkinje fibres
The Purkinje system is made up of individual cells, situated just below the endocardium. These cells directly stimulate the myocardium and initiate the ventricular depolarisation. - Bundle of His
The Bundle of His starts at the AV node and eventually becomes the right and left bundle branches. This runs on top of the intra-ventricular septum and continues down each side of the septum. The Bundle of His is the only direct route of communication between the right and left ventricles. - Left bundle branch
The left bundle branch also starts at the lower end of the Bundle of His and travels through the inter-ventricular septum and across the left ventricle. It initially depolarises the septum, which is the first part of the ventricles to be depolarised. The left bundle then breaks off to the left anterior and left posterior fascicle. - Right bundle branch
The right bundle branch starts at the His bundle and spreads across the right ventricle and right side of the inter-ventricular septum - Inferior vena cava
The inferior vena cava returns blood to the heart from the lower part of the body. - Interventricular septum
The intraventricular septum is the partition separating the right and left ventricles of the heart - Atrioventricular node (AV)
This is located in the wall of the right atrium, near the coronary sinus and leaflet of the tricuspid valve. It is responsible for slowing the impulses from the SA node before they reach the ventricles, long enough for atrial contraction to occur. The blood supply for the AV node comes from the right coronary artery. - Sinoatrial node (SA)
This is the main pacemaker for the heart and comprises of a mass of cells which spontaneously depolarises and generates action potentials faster than any other part of the conduction system. The SA node is located in the wall of the right atrial wall at its junction with the superior vena cava. Its blood supply comes predominately from the right coronary artery. It is the SA node which initiates each cardiac cycle and thus sets the basic pace of the heart rate. The pacemaker creates an organised beating of all cardiac cells in sequence to produce effective pumping of the heart.
Page last reviewed: 20 May 2020