Paramedics Course – ECG Electrical Conduction

Electrocardiogram (ECG) Electrical Conduction Lecture 2

Micro Lecture by the Australian Paramedical College

In today’s micro lecture, APC Hon. Snr. Lecturer Sam Willis introduces the electrical conduction system of the heart in when working with an electrocardiogram (ECG).


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Electrocardiogram (ECG) Electrical Conduction #2


In today’s micro-lecture we’re going to talk about the electrical conduction system of the heart.

Now every second of every day your heart generates electrical impulses, which leads to contractions of the atria and the ventricles, which is what pushes the blood around the body. It all starts here with the sinoatrial node, which is a group of specialized cardiac cells that sit in the wall of the right atria.

This group of specialised cells generate the first impulse which then moves systematically down to the second stage of the electrical conduction system known as the atrioventricular node.

Now when it does that it predominantly sends a signal downwards but also across as well. What you have to remember at this early point is that every single cell in the heart is called a myocyte and they are all highly specialised cells and when you trigger the cells they lead to a contraction, so they squeeze and contract the blood into the ventricles.

The sinoatrial node is where it all begins, also known as the pacemaker. You will have read about that or heard it in the reading materials. It pushes the, once the sinoatrial node has sent off the signal it moves down to this atrioventricular node.

From here it moves down the bundle of His of the atrioventricular bundle into these larger vessels known as the left bundle branch. This one here’s called the left bundle branch and this one here’s called the right bundle branch. Here it’s clearly labeled as the bundle branches, but if it’s on the left it’s the left bundle branch, if it’s on the right it’s the right bundle branch.

What you will clearly notice from this picture is the left bundle branch serves the left ventricle.

Now that’s a really important ventricle because it’s responsible for contracting the blood and pushing the blood out into the aorta and around the body.

That’s a pretty important ventricle but so is the right ventricle as well.

Now the smallest fibers on here are called the Purkinje fibers. That’s basically it, that is the electrical conduction system of the heart. It starts at the SA node, it goes down to the atrioventricular node, it goes down through the bundle of His into the left and right bundle branches, and into the Purkinje fibers.

As the pathway, as the electrical signal moves from the atria to the ventricles the atria contracts. Then as we move down the ventricular pathway the ventricles contract. That’s what you end up with consistently time and time again.

That’s a brief overview of the conduction system of the heart.

My name’s Sam Willis (Hon. Snr. Lecturer), I hope you’ve enjoyed this short micro-lecture and I look forward to talking to you again shortly.

Electrocardiogram (ECG) Electrical Conduction Lecture
Australian Paramedical College

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