Electrical conduction system of the heart: what it is and how it works

Have you ever wondered how the heart beats? For the heart to beat and pump blood to the different parts of our body, it operates through the so-called electrical conduction system of the heart.

In this article we will briefly explain what the human heart is like and how it works, What is the electrical conduction system of the heart and how does it work?. Finally, we will talk about arrhythmias, an alteration that occurs when this system fails.

• Related article: "The 13 parts of the human heart (and their functions)"

The heart

Before talking about the electrical conduction system of the heart, and how it works, we are going to briefly explain what the heart is and what its functions are.

The word heart comes from the Latin cor, and It is the main organ of the circulatory system.. The circulatory system is used to internally transport the different substances that living beings need to live: hormones, nutrients, oxygen, carbon dioxide...

Regarding its characteristics, the heart is a hollow muscular organ.

It works like a pump, pushing blood through the arteries., in order to distribute it throughout our body. Its size is that of a fist, and its weight is between 250 and 300 grams (in women) and 300 and 350 grams (in men). That is approximately 0.4% of our body weight. Anatomically, the heart is located in the center of the thoracic cavity, between the lungs.

Thus, the heart is the pump of the muscular tissue, which what it does is pump blood through the organism. On the other hand, the electrical conduction system of the heart coordinates the contraction of the different chambers from the heart.

structures of the heart

What structures are part of the heart, and therefore, the electrical conduction system of the heart? It is about 4:

• Right atrium (RA)
• Right Ventricle (RV)
• Left atrium (LA)
• left ventricle (LV)

Now yes, we are going to see how the electrical conduction system of the heart works.

electrical conduction system of the heart

The electrical conduction system of the heart has the main function of allow the blood pumped by the heart to be distributed throughout the body (that is, it is pumped throughout the body). It coordinates the contractions of the heart chambers so that it beats correctly.

More specifically, it is a system that allows the impulse generated by a heart node, the sinus node, to propagate and stimulate an important heart muscle, the myocardium. In this way, the latter contracts.

Thus, said system involves a series of coordinations of the myocardium, which cause the heart to contract efficiently, and, as we said, so the blood is pumped throughout the body.

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Components, location and operation

The main components of the electrical conduction system of the heart are two, the sinoatrial (SA) or sinus node and the atrioventricular node. We are going to explain what each one of them consists of, and how the electrical conduction system of the heart operates through said nodules (that is, how the heart beats):

1. Sinoatrial (SA) node

It could be said that the sinoatrial node is the natural pacemaker of the heart. This module is also called by other names, such as sinus node, Keith and Flack node, or heart pacemaker.. Anatomically, the SA is located in the upper posterior part of the right atrium of the heart, just at the entrance of the superior vena cava.

Regarding its characteristics, it is the largest cardiac pacemaker, and its shape is oval. It is in this nodule where the electrical impulse is born, which travels and spreads through the atria. It does so through pathways called internodal pathways, causing contraction of the atria.

In healthy adults, the sinus node discharges at a rate of 60 impulses per minute (60 contractions per minute); that is to say, that the electrical stimulus is generated regularly between 60 and 100 times per minute.

2. Atrioventricular (AV) node

It is then that the electrical impulse reaches the next node, the atrioventricular node (also called the Aschoff-Tawara node). Its size is 40% of the size of the previous nodule, the sinus. It is oval in shape, and located in the left part of the right atrium, specifically in a structure called interatrial septum.

Almost always (in 90% of cases), the atrioventricular node is supplied by a branch located in the right coronary artery. Said nodule It has two types of innervation: sympathetic and parasympathetic..

It is in the atrioventricular node where the electrical impulse (or electrical wave) stops for less than 1 second (specifically, for 0.13 seconds).

• You may be interested in: "Sympathetic nervous system: anatomy, functions and path"

And after that…?

After this pause in the electrical impulse in the atrioventricular node, the electrical impulse spreads through the bundle of His, a bundle of fibers which acts as a bridge between the nodule and the branches of the ventricles.

This beam is divided into two more branches: the right and the left. Another division appears on the left: the anterior left fascicle, the posterior left fascicle, and the median or septal fascicle. From In this last fascicle, the electrical impulse is distributed to the ventricles, through the Purkinje fibers., some fibers that allow ventricular contraction.

Abnormal functioning of the electrical conduction system of the heart

We have talked about how the electrical conduction system of the heart works in normal or healthy conditions, that is, when our heart beats normally and the different parts of the body receive the pumping of blood with normal.

But... what happens when there is a malfunction? Then situations or phenomena such as arrhythmias occur.

arrhythmias

an arrhythmia is a heart rate or heart rhythm disorder; In these cases, it may happen that the heart beats faster than usual (so we are talking about tachycardia), that it beats too slowly (bradycardia) or that it beats irregularly.

That is, arrhythmias involve abnormal beating of our heart. The arrhythmias themselves may not be harmful, although they are sometimes a sign of underlying problems, or an imminent danger to our health.

When and why do arrhythmias occur? They can occur in different cases and situations. The three most frequent are the following:

• When another part of the heart acts as a pacemaker (that is, it takes over this role).
• When our heart's natural pacemaker (ie the sinus node) produces an abnormal rhythm (rate).
• When the normal path of conduction is interrupted for any reason.

Symptoms

As we can see, when the heart's electrical conduction system fails, arrhythmias can appear. But, What symptoms does this disorder or heart rhythm disturbance produce? Arrhythmias mainly produce 4 symptoms: a feeling of shortness of breath, dizziness, fainting and palpitations.

To evaluate this problem, electrocardiogram (ECG) is used, which allows us to determine and analyze the rhythm of our heart. An ECG consists of a painless examination that allows the recording of cardiac electrical activity, through different electrodes placed on the chest.

Sometimes when the electrical rhythm is not normal, medication or surgery may even be needed. A specialist doctor should always be used to evaluate and treat our case.