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Cardiac Conduction System – Learn the Mechanism Behind Every Heartbeat

Updated on July 12, 2014

Cardiac conduction system is also referred to as the electrical conduction system of the heart. For an individual living for an average lifespan estimated for humans, the heart beats for 3 billion times. The cardiac conduction system of the heart is responsible for each and every normal heart beat. If the system fails to perform normally, it can lead to the serious issue called arrhythmias. Consider heart as a hard-working pump that requires electricity to operate. Learn how the system works to know the exact mechanism of why heart beats here:

Cardiac Conduction System: The Overview

Heart is made up of four chambers – two atrium chambers located above and two ventricle chambers located below. The blood collected from the body enters the two atrium chambers that purify it and contract to pass the purified blood to the two ventricle chambers. These two chambers contract further to pump the blood to lungs and other body parts. Now the question is that what makes these chambers to contract. This is where the role of cardiac conduction system comes into play. The system not only generates the electrical impulses but also relay them throughout the heart to depolarize (contract).

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Cardiac Conduction System: The Components

The most important components of the conduction system are:

  • Sinoatrial Node (SAN): Also called the heart’s pacemaker which generates the electrical impulses.
  • Atrioventricular Node (AVN): It performs the task of relaying the electrical impulses.
  • Bundle of His: It divides into Left and Right Bundle Branch (LBB and RBB) that carry the electrical impulses to ventricles.
  • Purkinje Fibers: The small fibers emerging out from LBB and RBB take the electrical impulses to each and every cell in the ventricles.

Cardiac Conduction System: How It Works?

AN, located in the right atrium produces electrical impulses that make the atrium chambers to contract. It is important to note that an important component called Bachmann’s Bundle carries the electrical signals to the left atrium. The process of contraction in atrium chambers is technically termed as atrium depolarization.

The electrical impulses produced at SAN are carried to AVN which is located between the atria and the ventricles. The node acts as a relay station of the cardiac conduction system and has the Bundle of His connected to it. The Bundle branches further into LBB and RBB that reach the left and the right ventricles respectively. The electrical signals from AVN pass through the Bundle of His and are carried further to the ventricles by LBB and RBB. The ventricles contract after receiving the signals and the process is called ventricle depolarization.

Purkinje fibers are small sub-branches of LBB and RBB that take the electrical signals to each of the thousands of ventricle cells. Another process which is a part of the cardiac conduction system is called repolarization of atriums and ventricles. During this process, the SAN and AVN nodes recharge to produce and coordinate another electrical signal.

Cardiac Conduction System: Heartbeat Statistics

The cardiac conduction system helps the heart to produce 60 to 70 beats per minute. This means that one beat is produced per second. It is interesting to note how this one second of every beat is divided:

  • Atrium Depolarization: One-third of a second
  • Ventricle Depolarization: One-third of a second
  • Repolarization: One-third of a second.

It is amazing to know how the whole system performs three different processes within one second of every heartbeat, while not putting the heart at rest. It is worth noting that different parts of the cardiac conduction system can generate 140-200 electrical signals (or heartbeats) per minute that are divided as:

  • SAN: 60-70
  • AVN (if SAN performs abnormally): 40-60
  • Bundle of His: 30-40
  • Ventricle cells: 20-30

The cardiac conduction system generates and coordinates the electrical impulses that accomplish normal functioning of the heart and the body. Electrocardiogram (ECG) is the machine used to monitor the cardiac conduction system in case the heart starts beating abnormally.


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