Purkinje fibers: Difference between revisions
subdivided the space they are located from just plain endocardium to specifically the subendocardium. Also included why the cells stain differently than other cardiac cells - b/c of increased glycogen and fewer myofibrils than other cardiac cells. |
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{{About||the nervous cells|Purkinje cell}} |
{{About||the nervous cells|Purkinje cell}} |
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The '''Purkinje fibers''' ('''Purkyne tissue''' or '''subendocardial branches''') are located in the inner [[Ventricle (heart)|ventricular]] walls of the [[heart]], just beneath the [[endocardium]]. These fibers consist of specialized [[myocardiocyte|cardiomyocytes]] that are able to conduct [[cardiac action potential]]s more quickly and efficiently than any other cells in the heart. Purkinje fibers allow the heart's [[electrical conduction system of the heart|conduction system]] to create [[cardiac rhythmicity|synchronized contractions]] of its ventricles, and are therefore essential for maintaining a consistent [[heart rhythm]]. |
The '''Purkinje fibers''' ('''Purkyne tissue''' or '''subendocardial branches''') are located in the inner [[Ventricle (heart)|ventricular]] walls of the [[heart]], just beneath the [[endocardium]] in a space called the subendocardium. These fibers consist of specialized [[myocardiocyte|cardiomyocytes]] that are able to conduct [[cardiac action potential]]s more quickly and efficiently than any other cells in the heart. Purkinje fibers allow the heart's [[electrical conduction system of the heart|conduction system]] to create [[cardiac rhythmicity|synchronized contractions]] of its ventricles, and are therefore essential for maintaining a consistent [[heart rhythm]]. |
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==Histology== |
==Histology== |
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Given no aberrant channels, the atrial and ventricular Purkinje fibers are distinctly shielded from each other by [[collagen]] or the [[cardiac skeleton]]. |
Given no aberrant channels, the atrial and ventricular Purkinje fibers are distinctly shielded from each other by [[collagen]] or the [[cardiac skeleton]]. |
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The Purkinje fibers are further specialized to rapidly conduct impulses (numerous fast [[voltage-gated ion channel|voltage-gated]] [[sodium channel]]s and [[mitochondria]], fewer [[myofibril]]s than the surrounding muscle tissue). Purkinje fibers take up stain differently from the surrounding muscle cells |
The Purkinje fibers are further specialized to rapidly conduct impulses (numerous fast [[voltage-gated ion channel|voltage-gated]] [[sodium channel]]s and [[mitochondria]], fewer [[myofibril]]s than the surrounding muscle tissue). Purkinje fibers take up stain differently from the surrounding muscle cells because of relatively fewer myofibrils than other cardiac cells and the presence of glycogen around the nucleus causes Purkinje fibers to appear, on a slide, lighter and larger than their neighbors. They are often binucleated cells. |
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==Function== |
==Function== |
Revision as of 14:21, 30 August 2013
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Purkinje fibers | |
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Identifiers | |
MeSH | D011690 |
TA98 | A12.1.06.008 |
TA2 | 3961 |
FMA | 9492 |
Anatomical terminology |
The Purkinje fibers (Purkyne tissue or subendocardial branches) are located in the inner ventricular walls of the heart, just beneath the endocardium in a space called the subendocardium. These fibers consist of specialized cardiomyocytes that are able to conduct cardiac action potentials more quickly and efficiently than any other cells in the heart. Purkinje fibers allow the heart's conduction system to create synchronized contractions of its ventricles, and are therefore essential for maintaining a consistent heart rhythm.
Histology
Purkinje fibers are a unique cardiac end-organ. Further histologic examination reveals that these fibers are split in atria and ventricles walls. The electrical origin of atrial Purkinje fibers arrives from the sinoatrial node.
Given no aberrant channels, the atrial and ventricular Purkinje fibers are distinctly shielded from each other by collagen or the cardiac skeleton.
The Purkinje fibers are further specialized to rapidly conduct impulses (numerous fast voltage-gated sodium channels and mitochondria, fewer myofibrils than the surrounding muscle tissue). Purkinje fibers take up stain differently from the surrounding muscle cells because of relatively fewer myofibrils than other cardiac cells and the presence of glycogen around the nucleus causes Purkinje fibers to appear, on a slide, lighter and larger than their neighbors. They are often binucleated cells.
Function
Heart rate is governed by many influences from the Autonomic Nervous System. The Purkinje Fibers do not have any known role in setting heart rate, but are influenced by electrical discharge from the Sinoatrial node.
During the ventricular contraction portion of the cardiac cycle, the Purkinje fibers carry the contraction impulse from both the left and right bundle branch to the myocardium of the ventricles. This causes the muscle tissue of the ventricles to contract, thus enabling a force to eject blood out of the heart; either to the Pulmonary circulation from the right ventricle or to the Systemic circulation from the left ventricle.
Purkinje fibers also have the ability of firing at a rate of 15-40 beats per minute if left to their own devices. In contrast, the SA node in normal state can fire at 60-100 beats per minute. In short, they generate action potentials, but at a slower rate than sinoatrial node. Thus they serve as the last resort when other pacemakers fail. When a pukinje fiber does fire, it is called a premature ventricular contraction or PVC, or in other situations can be a ventricular escape . It plays a vital role in the circulatory system.
Etymology
They were discovered in 1839 by Jan Evangelista Purkyně, who gave them his name.
References
External links
- Template:EMedicineDictionary
- Anatomy photo: Circulatory/heart/purkinje/purkinje1 - Comparative Organology at University of California, Davis - "Mammal heart, purkinje fibers (LM, Medium)"
- Anatomy Atlases – Microscopic Anatomy, plate 05.78
- MedEd at Loyola Histo/practical/cardio/hp8-21.html
- Histology at ucsd.edu
- Histology at nhmccd.edu
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