transverse tubule

T管

WordNet

1. a small tube

PrepTutorEJDIC

1. 横の,横断の;(線など)交わる / (幾何で)横軸の / 横断するもの(特に道路など) / (幾何で)横軸
2. 小管,細管

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/11/09 10:45:13」(JST)

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T-tubule
Latin	tubulus transversus
Code	TH H2.00.05.2.01018 TH H2.00.05.2.02013

A T-tubule (or transverse tubule) is a deep invagination of the sarcolemma, which is the plasma membrane, only found in skeletal and cardiac muscle cells. These invaginations allow depolarization of the membrane to quickly penetrate to the interior of the cell.

Structure

Each muscle fibre is surrounded by a sarcolemma (the muscle fiber's plasma membrane). Transverse tubules are invaginations of the sarcolemma. Though the invaginations are normally perpendicular to the length of the fiber, many T-tubules can lie axial to the long-axis of the fiber, both wrapping around and running alongside myofilament bundles. The size and arrangement of T-tubules vary depending on muscle type and species. T-tubules are thought to be rich in a number of proteins, including a large number of L-type calcium channels.

In skeletal muscle cells, T-tubules are typically located at the junction overlap between the A and I bands of the sarcomere, and together with a pair of terminal cisternae (bulbous enlarged areas of the sarcoplasmic reticulum) it forms an arrangement called a triad.

In cardiac muscle, the T-tubule membrane is normally opposed to a single terminal cisterna, which may wrap around the T-tubule. This occurs at the Z line and is called a diad.

It is physiologically important for excitation-contraction coupling (see section below) that the T-tubules are positioned close to the terminal cisternae of the sarcoplasmic reticulum as the triad or diad arrangement allows physical and functional contact by voltage dependent L-type calcium channels. So, an action potential along the sarcolemma causes calcium channels to open in the terminal cisternae/sarcoplasmic reticulum which enables calcium to move from the sarcoplasmic reticulum into cytoplasm and the intracellular calcium concentration to increase.

Excitation-contraction coupling

See Excitation-contraction coupling

T-tubules are the major sites for the coupling of excitation and contraction, which is the process whereby the spreading depolarization is converted into force production by muscle fibers. The L-type calcium channels in T-tubules activate in response to electrical stimulation; their opening allows calcium to flow down its electrochemical gradient and into the cell. Activation of the L-type channel also causes a mechanical interaction between it and calcium-release channels located on the adjacent sarcoplasmic reticulum membrane.

In skeletal muscle, the influx of calcium through the L-type calcium channel on the T-tubule contributes little to excitation-contraction coupling, whereas it is crucial to the proper function of cardiac muscle (see Cardiac action potential). Conversely, the mechanical interaction between the T-tubule's L-type calcium channel and the calcium-release channel is critical to proper skeletal muscle contraction, whereas it contributes little to the contraction of cardiac muscle.

Detubulation

It is possible to physically and functionally uncouple T-tubules from the surface membrane using a technique known as detubulation. This relies on osmotically active chemicals, such as glycerol (for skeletal muscle) or formamide (mainly for cardiac muscle). Addition of these chemicals to the solution surrounding muscle cells causes the cells to shrink; when the chemical is withdrawn the cells rapidly expand before returning to their normal size. The rapid expansion is thought to cause the t-tubules to detach from the surface membrane, which reseals, and to reseal within the cell. This technique can be used to investigate the function of the t-tubules.

There is some evidence that heart failure precipitates the loss of the T-tubule network, again indicating their importance.^{[citation needed]}

See also

• Muscle contraction

References

External links

• BU Histology Learning System: 22502loa - "Ultrastructure of the Cell: cardiac muscle, intercalated disk "
• T+tubule at eMedicine Dictionary
• Physiology at MCG 2/2ch3/communic

UpToDate Contents

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• 1. Chapter 5A：遠位尿細管と接合部分 chapter 5a distal tubule and connecting segment
• 2. 後頭横位 occiput transverse position
• 3. バーター症候群およびギテルマン症候群 bartter and gitelman syndromes
• 4. 悪性高熱症：臨床診断および急性期のマネージメント malignant hyperthermia clinical diagnosis and management of acute crisis
• 5. 左室肥大および不整脈 left ventricular hypertrophy and arrhythmia

English Journal

• Emerging mechanisms of T-tubule remodeling in heart failure.

• Guo A, Zhang C, Wei S, Chen B, Song LS.SourceDivision of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA 52242.
• Cardiovascular research.Cardiovasc Res.2013 Feb 7. [Epub ahead of print]
• Cardiac excitation-contraction coupling occurs primarily at the sites of transverse (T)-tubule / sarcoplasmic reticulum junctions. The orderly T-tubule network guarantees the instantaneous excitation and synchronous activation of nearly all Ca(2+) release sites throughout the large ventricular myocy
• PMID 23393229

• CALCIUM SIGNALLING MICRODOMAINS AND THE T-TUBULAR SYSTEM IN ATRIAL MYCOYTES: POTENTIAL ROLES IN CARDIAC DISEASE AND ARRHYTHMIAS.

• Trafford AW, Clarke JD, Eisner DA, Dibb KM.AbstractThe atria contribute 25 % to ventricular stroke volume and are the site of the commonest cardiac arrhythmia, atrial fibrillation (AF). The initiation of contraction in the atria is similar to that in ventricle involving a systolic rise of intracellular Ca(2+) concentration ([Ca(2+)](i)). There are, however, substantial inter-species differences in the way systolic Ca(2+) is regulated in atrial cells. These differences are a consequence of a well-developed and functionally relevant transverse (t) - tubule network in the atria of large mammals including man and its virtual absence in smaller laboratory species such as the rat. Where t-tubules are absent the systolic Ca(2+) transient results from a 'fire-diffuse-fire' sequential recruitment of Ca(2+) release sites from the cell edge to the centre and hence marked spatiotemporal heterogeneity of systolic Ca(2+). Conversely the well-developed t-tubule network in large mammals ensures a near synchronous rise of [Ca(2+)](i). In addition to synchronizing the systolic rise of [Ca(2+)](i) the presence of t-tubules in the atria of large mammals, by virtue of localization of the L-type Ca(2+) channels and Na(+)-Ca(2+) exchanger antiporters on the t-tubules, may serve to respectively accelerate changes in the amplitude of the systolic Ca(2+) transient during inotropic manoeuvres and lower diastolic [Ca(2+)](i). On the other hand, the presence of t-tubules and thence wider cellular distribution of the Na(+)-Ca(2+) exchanger may predispose the atria of large mammals to Ca(2+) dependent delayed after-depolarisations (DADs); this may be a determining factor in why the atria of large mammals spontaneously develop and maintain AF.
• Cardiovascular research.Cardiovasc Res.2013 Feb 5. [Epub ahead of print]
• The atria contribute 25 % to ventricular stroke volume and are the site of the commonest cardiac arrhythmia, atrial fibrillation (AF). The initiation of contraction in the atria is similar to that in ventricle involving a systolic rise of intracellular Ca(2+) concentration ([Ca(2+)](i)). There are,
• PMID 23386275

Japanese Journal

• Pacing-Induced Non-Uniform Ca2+ Dynamics in Rat Atria Revealed by Rapid-Scanning Confocal Microscopy

• Jiang Yan,Tanaka Hideo,Matsuyama Taka-aki,Yamaoka Yoshihisa,Takamatsu Tetsuro
• ACTA HISTOCHEMICA ET CYTOCHEMICA, 2014
• Intracellular Ca2+ ([Ca2+]i) dynamics in isolated myocytes differ between the atria and ventricles due to the distinct t-tubular distributions. Although cellular aspects of ventricular [Ca2+]i dynamic …
• NAID 130003390850

• タツナミガイ体壁網状筋の興奮収縮連関と収縮-弛緩に伴う細胞内Ca動態に関する生理学および細胞化学的研究

• 川村 秀二,田原 聖一,今井 政直 [他],Tahara Seiichi,今井 政直,Imai Masanao,望月 大影,Mochizuki Hiroaki,鈴木 季直,Suzuki Suechika
• 神奈川大学理学誌 20(1), 65-76, 2009
• … The plasma membrane of RBWM fibers frequently showedtubular invaginations, closely resembling the transverse tubules (T tubule) of skeletal muscle. …
• NAID 120002114209

• FRS-113 T-tubule System is a Major Supporting Structure Against the Transverse Mechanical Stress in Cardiac Myocytes(New Concepts for Assessing Cardiac Function(M),Featured Research Session,The 72nd Annual Scientific Meeting of the Japanese Circulation Society)

• Kurokawa Hiroshi,Seo Kinya,Nishimura Satoshi,Hosoya Yumiko,Yamashita Hiroshi,Sugiura Seiryou
• Circulation journal : official journal of the Japanese Circulation Society 72(Supplement_I), 175, 2008-03-01
• NAID 110006797192

Related Links

• T-tubule - Wikipedia, the free encyclopedia

A T-tubule (or transverse tubule) is a deep invagination of the sarcolemma, which is the plasma membrane, only found in skeletal and cardiac muscle cells. These invaginations allow depolarization of the membrane to quickly penetrate to the ...

• Sarcoplasmic Reticulum Structure & Function | Transverse Tubules ...

A tutorial on the structure and function of sarcoplasmic reticulum and T-tubules in skeletal muscle fibers, using interactive animations and diagrams.

Related Pictures

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★リンクテーブル★

リンク元	「T管」
関連記事	「transverse」「tubule」

「T管」

　　[★]

英

T tubule (K)

同

T細管、横細管 transverse tubule tubulus transversus

[show details]

T tubule T管: 約 75件
T tubule T細管: 約 16件

「transverse」

　　[★]

• adj.

• 横行の、横行性の、横径の、横断した

関

cross、crossing、transect、transversal、transverse diameter、transversely

　

「tubule」

　　[★]

• n.

• 尿細管、細管

関

canaliculi、canaliculus、kidney tubule、renal tubular、renal tubule、tubular、uriniferous tubule