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What are Purkinje Fibers?

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  • Written By: Douglas Bonderud
  • Edited By: Michelle Arevalo
  • Last Modified Date: 16 May 2019
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Purkinje fibers are specialized muscle fibers found in the heart. They originate at the atrioventricular bundle and extend into the ventricles. Their function is to relay impulses from the bundle to the ventricles, causing a contraction. They do so at a speed of between three ft (one m) and 12 ft (four m) per second, causing the contraction of the ventricles to be almost instantaneous.

These fibers, also known as subendocardial branches, are located beneath the endocardium, which is the innermost layer of the heart. Purkinje fibers are stretched along heart muscle tissue beginning at the atrioventricular node. They then proceed down the middle portion of the heart and branch out to either side at the bottom, curving up along the outer edge of the endocardial wall.

When an electrical impulse is sent along the Purkinje fibers, it is rapidly relayed to the ventricular cells on both sides of the heart. This in turn causes the ventricles to contract. The contracting ventricles produce enough force to eject blood from the heart, which is necessary for circulation. Pulmonary circulation originates from the right ventricle, and systemic circulation comes from the left. If stained and viewed under a microscope, Purkinje fibers will appear larger and lighter than the surrounding muscle tissue.

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Named after the Czechoslovakian anatomist Jan Evangelista Purkyne, Purkinje fibers were discovered in 1839. Purkyne, spelled alternatively at Purkinje, also discovered Purkinje cells, which are large neurons located in the cerebellum. In addition, he is credited with the discovery that red-colored objects appear to fade faster in dim light conditions than those that are blue. This is known as the Purkinje effect.

Purkinje was extremely active in the scientific community of his time. He coined the term plasma, which refers to blood that has had all of the suspended cells within it removed, and protoplasm, which is the substance within the cells. In 1823, Purkinje published a paper on the structure of fingerprints and their anatomical makeup. Although his primary focus was physiology, he also made forays into the world of experimental psychology.

During his lifetime, Purkinje made at least six significant discoveries that now bear his name. In the early part of the 17th century, Purkinje was famous enough that any letters addressed to him simply needed to contain his name and the word 'Europe.' He is said to have founded the first physiology department in the world, followed shortly thereafter by the first physiology laboratory.

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anon1000925
Post 4

Heart muscle cells can contract, but in order to efficiently pump blood it is important that all of the cells in the atria and then all of the cells in the ventricles contract at the same time. This coordination is achieved by the electrical conduction system of the heart; the Purkinje fibers are the end parts of that system.

The impulse originates in the Sino-Atrial node, in the wall of the right atrium. This starts the depolarization of the cells in the atria so that it will contract, squeezing the blood into the ventricles. When the contracting impulse gets through the atrial cells over to the other side of the chamber, where they touch the Atrial Ventricular node, that

conducts the impulse to the rest of the electrical conduction system. The AV node continues into the AV bundle, then into right and left bundle branches to go around the right and left ventricles. The Purkinje fibers come off of the bundle branches to bring the impulse deep into the muscle tissue.

Picture something like a length of yarn (the bundle branch) with fibers splitting off to the sides and from the ends (the purkinje fibers). The impulse travels so swiftly along this specialized pathway that all of the cardiac muscle cells in the ventricles receive the impulse and contract at virtually the same time, efficiently pumping the blood out to the rest of the body.

Izzy78
Post 2

@matthewc23 - Considering that the heart requires an electrical impulse in order to circulate blood I would think that that is their primary function and they are in fact part of a number of things in order for blood to move about the body.

There has to be something that causes the heart to contract and pump blood and I am guessing that these fibers serve as the primary function that is required for blood to circulate out of the heart and through the rest of the body.

What i would like to know is what is it that works in conjunction with these fibers in order for that function to occur and how the process fully works. I guess it would be a lesson in how blood circulates through the body but I feel that it would be beneficial in further explaining the role in how the purkinje fibers operate.

matthewc23
Post 1

Although I find this article interesting I have to wonder exactly what the role of the purkinje fibers are. I know that they send electrical impulses into the ventricles, I understood that part, but are they the part of the heart that causes the muscles in the heart to contract and pump blood or is it something else.

I know that there are many different functions of the body and that a number of different things cause everything to function the way they do but after reading this article the role of these fibers is completely lost of me. I really want to know why they are so important.

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