Anatomy
Cardiac Conducting System
What is the Cardiac Conducting System
The cardiac conducting system consists of a network of conducting fibres situated within the inner aspect of the cardiac chambers. The fibres are responsible for transporting the signals from pacemaker cells in a rapid manner through both atria and ventricles, so that a coordinated contraction can be achieved
The anatomy of the conducting system is very important to understand, because it forms the basis of the traces within the ECG. Click on the video to see how it functions.
Pathway For Electrical Signals
The depolarisation wave spreads across both atria from the SAN, via gap junctions, causing them to contract and empty blood into the ventricles. A small tract of conducting tissue called Bachman's bundle allows the electrical activity to spread through the inter-atrial septum into the left atrium
When the depolarisation wave reaches the Atrio-ventricular (AV) node, the node delays the signal for a short period of time. This allows the ventricles to fill with blood before they are given the signal to contract.
The wave then spreads down through the Bundle of His, and divides between the left and right bundle branches fanning out throughout the rest of the ventricles simultaneously via small Purkinje fibres.
In a well-functioning system, the apex of the heart should contract before the upper portions of the ventricles. That way, the blood will be forced in an upwards direction through the aorta and pulmonary vessels.
