WordNet

tell a relatively insignificant lie; "Fibbing is not acceptable, even if you dont call it lying"
a trivial lie; "he told a fib about eating his spinach"; "how can I stop my child from telling stories?" (同)story, tale, tarradiddle, taradiddle
a slender and greatly elongated substance capable of being spun into yarn (同)fibre
a leatherlike material made by compressing layers of paper or cloth (同)fibre, vulcanized fiber
any of several elongated, threadlike cells (especially a muscle fiber or a nerve fiber) (同)fibre
Bohemian physiologist remembered for his discovery of Purkinje cells and the Purkinje network (1787-1869) (同)Jan Evangelista Purkinje, Johannes Evangelista Purkinje

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/07/30 19:05:02」(JST)

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The Purkinje fibers (/pərˈkɪndʒiː/ pər-KIN-jee) (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 and generate 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 upstream conduction or pacemaking ability is compromised. 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. This capability is normally suppressed. Thus, they serve as the last resort when other pacemakers fail. When a Purkinje 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

subendocardial+branches+of+atrioventricular+bundles at eMedicine Dictionary
Organology at UC Davis Circulatory/heart/purkinje/purkinje1 - "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

UpToDate Contents

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English Journal

Mapping the development of cerebellar Purkinje cells in zebrafish.

Hamling KR1, Tobias ZJ1, Weissman TA1.
Developmental neurobiology.Dev Neurobiol.2015 Nov;75(11):1174-88. doi: 10.1002/dneu.22275. Epub 2015 Feb 18.
The cells that comprise the cerebellum perform a complex integration of neural inputs to influence motor control and coordination. The functioning of this circuit depends upon Purkinje cells and other cerebellar neurons forming in the precise place and time during development. Zebrafish provide a us
PMID 25655100

Oxygen-glucose deprivation increases firing of unipolar brush cells and enhances spontaneous EPSCs in Purkinje cells in the vestibulo-cerebellum.

Takayasu Y1, Shino M2, Nikkuni O2, Yoshida Y3, Furuya N2, Chikamatsu K2.
Neuroscience research.Neurosci Res.2015 Nov 1. pii: S0168-0102(15)00260-6. doi: 10.1016/j.neures.2015.10.009. [Epub ahead of print]
Unipolar brush cells (UBCs) are excitatory interneurons in the granular layer of the cerebellar cortex, which are predominantly distributed in the vestibulo-cerebellar region. The unique firing properties and synaptic connections of UBCs may underlie lobular heterogeneity of excitability in the gran
PMID 26535811

Purkinje cell activity during classical conditioning with different conditional stimulus explains central tenet of Rescorla-Wagner model.

Rasmussen A1, Zucca R2, Johansson F3, Jirenhed DA3, Hesslow G3.
Proceedings of the National Academy of Sciences of the United States of America.Proc Natl Acad Sci U S A.2015 Oct 26. pii: 201516986. [Epub ahead of print]
A central tenet of Rescorla and Wagner's model of associative learning is that the reinforcement value of a paired trial diminishes as the associative strength between the presented stimuli increases. Despite its fundamental importance to behavioral sciences, the neural mechanisms underlying the mod
PMID 26504227

Japanese Journal

Regulation and functional roles of rebound potentiation at cerebellar stellate cell—Purkinje cell synapses

Hirano Tomoo,Kawaguchi Shin-ya
Frontiers in Cellular Neuroscience 8, 2014-02-18
… Purkinje cells receive both excitatory and inhibitory synaptic inputs and send sole output from the cerebellar cortex. … Long-term depression (LTD), a type of synaptic plasticity, at excitatory parallel fiber–Purkinje cell synapses has been studied extensively as a primary cellular mechanism of motor learning. … On the other hand, at inhibitory synapses on a Purkinje cell, postsynaptic depolarization induces long-lasting potentiation of GABAergic synaptic transmission. …
NAID 120005385884

Long-term Potentiation of Inhibitory Synaptic Transmission onto Cerebellar Purkinje Neurons Contributes to Adaptation of Vestibulo-Ocular Reflex.

Tanaka Shinsuke,Kawaguchi Shin-Ya,Shioi Go,Hirano Tomoo
The Journal of neuroscience : the official journal of the Society for Neuroscience 33(43), 17209-17220, 2013-10-23
… In particular, long-term depression (LTD) at parallel fiber (PF) to Purkinje neuron (PN) excitatory synapses has attracted much attention of neuroscientists as a primary cellular mechanism for motor learning. …
NAID 120005342657