(Nurse Cheung) ELECTRICAL CONDUCTION SYSTEM OF THE HEART

Starting Point: Sinoatrial node (SA node)

60-100 bpm

Located in the right atrium, close to where it meets the superior vena cava. This node is essential when it comes to the heart’s primary pacemaker, marking the act of the electrical conduction pathway

The activation of the SA node triggers what?

A sequential contraction of atrial myocytes. The role of the fibrous tissue found in the septum which separates the right and left sides of our hearts including our atria and ventricle.

This separation is vital as it hinders direct electrical signal transmission between those heart sections

Following the SA node, we encounter a structure known as what?

Bachman bundle. It is characterized by its ability to transmit high speed signals extending from the SA node across the atrial septal wall and into our left atria

The internodal pathway consists of three routes:

The anterior, middle and posterior. These pathways are chiefly involved in conveying that electrical impulse from the SA node all the way to atrioventricular node

Where is the atrioventricular node located? 40-60 bpm

Is situated in the right atrium near the coronary sinus and the tricuspid valve. The clusters of cells is specialized to momentarily pause that electrical signal from the SA node before it can proceed down into the ventricles

This delay is crucial because it provides sufficient time for the atria to contract and make sure all of the blood is going to reach the ventricles before the ventricles themselves contract

Following the AV node we encounter what?

The bundle of His, which is comprised of another group of high speed transmission cells, they extend from the AV node to the right atrium, then to our interventricular septum where it’s going to branch off to our left and right ventricles.

The bundle of his is going to split off into two distinct pathways:

The bundle of his is the only route between the atria and ventricles. The two pathways are our right bundle branch and our left bundle branch. The right bundle branch transmits signals to our right ventricle and the left bundle branch transmits signals to the left ventricle

What projects from the right and left bundle branches?

Purkinje fibers, and they connect with the heart’s myocytes. Their primary role is to initiate depolarization within the muscle cells triggering that contraction that we see in the cardiac muscle