Cardiac muscle - wikipedia Cardiac muscle Cardiac muscle Details Part of Myocardium of the heart Identifiers Latin Textus muscularis striatus cardiacus TH H2. 00.05. 2.02001, H2. 00.05. 2.00004 FMA 14068 Anatomical terminology ( edit on Wikidata ) Play media An isolated cardiac muscle cell, beating Cardiac muscle ( heart muscle ) is an involuntary, striated muscle that is found in the walls and histological foundation of the heart, specifically the myocardium. Cardiac muscle is one of three major types of muscle, the others being skeletal and smooth muscle. These three types of muscle all form in the process of myogenesis. The cells that constitute cardiac muscle, called cardiomyocytes or myocardiocytes, predominantly contain only one nucleus, although populations with two to four nuclei do exist. The myocardium is the muscle tissue of the heart, and forms a thick middle layer between the outer epicardium layer and the inner endocardium layer. Coordinated contractions of cardiac muscle cells in the heart pump blood out of the atria and ventricles to the blood vessels of the left / body / systemic and right / lungs / pulmonary circulatory systems. This complex mechanism illustrates systole of the heart. Cardiac muscle cells, unlike most other tissues in the body, rely on an available blood and electrical supply to deliver oxygen and nutrients and remove waste products such as carbon dioxide. The coronary arteries help fulfill this function. Contents 1 Structure 1.1 Striation 1.2 T - tubules 1.3 Intercalated discs 2 Physiology 2.1 Regeneration 3 Clinical significance 4 See also 5 References 6 External links Structure Cardiac muscle Intercalated discs are part of the cardiac muscle sarcolemma and they contain gap junctions and desmosomes. 3D rendering showing thick myocardium within heart wall. Striation Cardiac muscle has cross striations formed by rotating segments of thick and thin protein filaments. Like skeletal muscle, the primary structural proteins of cardiac muscle are myosin and actin. The actin filaments are thin, causing the lighter appearance of the I bands in striated muscle, whereas the myosin filament is thicker, lending a darker appearance to the alternating A bands as observed with electron microscopy. However, in contrast to skeletal muscle, cardiac muscle cells are typically branch - like instead of linear. T - tubules Another histological difference between cardiac muscle and skeletal muscle is that the T - tubules in the cardiac muscle are bigger and wider and track laterally to the Z - discs. There are fewer T - tubules in comparison with skeletal muscle. The diad is a structure in the cardiac myocyte located at the sarcomere Z - line. It is composed of a single T - tubule paired with a terminal cisterna of the sarcoplasmic reticulum. The diad plays an important role in excitation - contraction coupling by juxtaposing an inlet for the action potential near a source of Ca ions. This way, the wave of depolarization can be coupled to calcium - mediated cardiac muscle contraction via the sliding filament mechanism. Cardiac muscle forms these instead of the triads formed between the sarcoplasmic reticulum in skeletal muscle and T - tubules. T - tubules play critical role in excitation - contraction coupling ( ECC ). Recently, the action potentials of T - tubules were recorded optically by Guixue Bu et al. Intercalated discs Main article : Intercalated disc The cardiac syncytium is a network of cardiomyocytes connected to each other by intercalated discs that enable the rapid transmission of electrical impulses through the network, enabling the syncytium to act in a coordinated contraction of the myocardium. There is an atrial syncytium and a ventricular syncytium that are connected by cardiac connection fibres. Electrical resistance through intercalated discs is very low, thus allowing free diffusion of ions. The ease of ion movement along cardiac muscle fibers axes is such that action potentials are able to travel from one cardiac muscle cell to the next, facing only slight resistance. Each syncytium obeys the all or none law. Intercalated discs are complex adhering structures that connect the single cardiomyocytes to an electrochemical syncytium ( in contrast to the skeletal muscle, which becomes a multicellular syncytium during mammalian embryonic development ). The discs are responsible mainly for force transmission during muscle contraction. Intercalated discs consist of three different types of cell - cell junctions : the actin filament anchoring adherens junctions, the intermediate filament anchoring desmosomes, and gap junctions. They allow action potentials to spread between cardiac cells by permitting the passage of ions between cells, producing depolarization of the heart muscle. However, novel molecular biological and comprehensive studies unequivocally showed that intercalated discs consist for the most part of mixed - type adhering junctions named area composita ( pl. areae compositae ) representing an amalgamation of typical desmosomal and fascia adhaerens proteins ( in contrast to various epithelia ). The authors discuss the high importance of these findings for the understanding of inherited cardiomyopathies ( such as arrhythmogenic right ventricular cardiomyopathy ). Under light microscopy, intercalated discs appear as thin, typically dark - staining lines dividing adjacent cardiac muscle cells. The intercalated discs run perpendicular to the direction of muscle fibers. Under electron microscopy, an intercalated disc 's path appears more complex. At low magnification, this may appear as a convoluted electron dense structure overlying the location of the obscured Z - line. At high magnification, the intercalated disc 's path appears even more convoluted, with both longitudinal and transverse areas appearing in longitudinal section. Physiology Main article : Excitation - contraction coupling The physiology of cardiac muscle shares many similarities with that of skeletal muscle. The primary function of both muscle types is to contract, and in both cases a contraction begins with a characteristic flow of ions across the cell membrane known as an action potential. The action potential subsequently triggers muscle contraction by increasing the concentration of calcium within the cytosol. However, the mechanism by which calcium concentrations within the cytosol rise differ between skeletal and cardiac muscle. In cardiac muscle, the action potential comprises an inward flow of both sodium and calcium ions. The flow of sodium ions is rapid but very short - lived, while the flow of calcium is sustained and gives the plateau phase characteristic of cardiac muscle action potentials. The comparatively small flow of calcium through the L - type calcium channels triggers a much larger release of calcium from the sarcoplasmic reticulum in a phenomenon known as calcium - induced calcium release. In contrast, in skeletal muscle, minimal calcium flows into the cell during action potential and instead the sarcoplasmic reticulum in these cells is directly coupled to the surface membrane. This difference can be illustrated by the observation that cardiac muscle fibres require calcium to be present in the solution surrounding the cell in order to contract, while skeletal muscle fibres will contract without extracellular calcium. During contraction of a cardiac muscle cell, the long protein myofilaments oriented along the length of the slide over each other in what is known as the sliding filament hypothesis. There are two kinds of myofilaments, thick filaments composed of the protein myosin, and thin filaments composed of the proteins actin, troponin and tropomyosin. As the thick and thin filaments slide past each other the cell becomes shorter and fatter. In a mechanism known as crossbridge cycling, calcium ions bind to the protein troponin, which along with tropomyosin then uncover key binding sites on actin. Myosin, in the thick filament, can then bind to actin, pulling the thick filaments along the thin filaments. When the concentration of calcium within the cell falls, troponin and tropomyosin once again cover the binding sites on actin, causing the cell to relax. Regeneration Dog cardiac muscle ( 400X ) Until recently, it was commonly believed that cardiac muscle cells could not be regenerated. However, a study reported in the April 3, 2009 issue of Science contradicts that belief. Olaf Bergmann and his colleagues at the Karolinska Institute in Stockholm tested samples of heart muscle from people born before 1955 who had very little cardiac muscle around their heart, many showing with disabilities from this abnormality. By using DNA samples from many hearts, the researchers estimated that a 4 - year - old renews about 20 % of heart muscle cells per year, and about 69 percent of the heart muscle cells of a 50 - year - old were generated after he or she was born. One way that cardiomyocyte regeneration occurs is through the division of pre-existing cardiomyocytes during the normal aging process. The division process of pre-existing cardiomyocytes has also been shown to increase in areas adjacent to sites of myocardial injury. In addition, certain growth factors promote the self - renewal of endogenous cardiomyocytes and cardiac stem cells. For example, insulin - like growth factor 1, hepatocyte growth factor, and high - mobility group protein B1 increase cardiac stem cell migration to the affected area, as well as the proliferation and survival of these cells. Some members of the fibroblast growth factor family also induce cell - cycle re-entry of small cardiomyocytes. Vascular endothelial growth factor also plays an important role in the recruitment of native cardiac cells to an infarct site in addition to its angiogenic effect. Based on the natural role of stem cells in cardiomyocyte regeneration, researchers and clinicians are increasingly interested in using these cells to induce regeneration of damaged tissue. Various stem cell lineages have been shown to be able to differentiate into cardiomyocytes, including bone marrow stem cells. For example, in one study, researchers transplanted bone marrow cells, which included a population of stem cells, adjacent to an infarct site in a mouse model. Nine days after surgery, the researchers found a new band of regenerating myocardium. However, this regeneration was not observed when the injected population of cells was devoid of stem cells, which strongly suggests that it was the stem cell population that contributed to the myocardium regeneration. Other clinical trials have shown that autologous bone marrow cell transplants delivered via the infarct - related artery decreases the infarct area compared to patients not given the cell therapy. Clinical significance Occlusion ( blockage ) of the coronary arteries by atherosclerosis and / or thrombosis can lead to myocardial infarction ( heart attack ), where part of the myocardium is injured due to ischemia ( not receiving enough oxygen ). This occurs because coronary arteries are functional end arteries - i.e. there is almost no overlap in the areas supplied by different arteries ( anastomoses ) so that if one fails, others can not adequately perfuse the region, unlike in other tissues. Certain viruses lead to myocarditis ( inflammation of the myocardium ). Cardiomyopathies are inherent diseases of the myocardium, many of which are caused by genetic mutations. See also Wikimedia Commons has media related to Cardiac muscle. This article uses anatomical terminology ; for an overview, see Anatomical terminology. Frank -- Starling law of the heart Regional function of the heart Nebulette References Jump up ^ Olivetti G, Cigola E, Maestri R, et al. ( July 1996 ). `` Aging, cardiac hypertrophy and ischemic cardiomyopathy do not affect the proportion of mononucleated and multinucleated myocytes in the human heart ''. Journal of Molecular and Cellular Cardiology. 28 ( 7 ) : 1463 -- 77. PMID 8841934. doi : 10.1006 / jmcc. 1996.0137. Jump up ^ Pollard, Thomas D. and Earnshaw, William. C., `` Cell Biology ''. Philadelphia : Saunders. 2007. Jump up ^ Bu G, Adams H, Berbari EJ, Rubart M ( March 2009 ). `` Uniform action potential repolarization within the sarcolemma of in situ ventricular cardiomyocytes ''. Biophys. J. 96 ( 6 ) : 2532 -- 46. PMC 2907679. PMID 19289075. doi : 10.1016 / j. bpj. 2008.12. 3896. Jump up ^ Jahangir Moini ; Professor of Allied Health Everest University Indialantic Florida Jahangir Moini ( 4 April 2011 ). Anatomy and Physiology for Health Professionals. Jones & Bartlett Publishers. pp. 213 --. ISBN 978 - 1 - 4496 - 3414 - 8. Jump up ^ Khurana ( 1 January 2005 ). Textbook Of Medical Physiology. Elsevier India. p. 247. ISBN 978 - 81 - 8147 - 850 - 4. Jump up ^ Franke WW, Borrmann CM, Grund C, Pieperhoff S ( February 2006 ). `` The area composita of adhering junctions connecting heart muscle cells of vertebrates. I. Molecular definition in intercalated disks of cardiomyocytes by immunoelectron microscopy of desmosomal proteins ''. Eur. J. Cell Biol. 85 ( 2 ) : 69 -- 82. PMID 16406610. doi : 10.1016 / j. ejcb. 2005.11. 003. Jump up ^ Goossens S, Janssens B, Bonné S, et al. ( June 2007 ). `` A unique and specific interaction between alphaT - catenin and plakophilin - 2 in the area composita, the mixed - type junctional structure of cardiac intercalated discs ''. J. Cell. Sci. 120 ( Pt 12 ) : 2126 -- 36. PMID 17535849. doi : 10.1242 / jcs. 004713. Jump up ^ Pieperhoff S, Barth M, Rickelt S, Franke WW ( 2010 ). Mahoney MG, Müller EJ, Koch PJ, eds. `` Desmosomes and Desmosomal Cadherin Function in Skin and Heart Diseases - Advancements in Basic and Clinical Research ''. Dermatol Res Pract. 2010 : 1. PMC 2946574. PMID 20885972. doi : 10.1155 / 2010 / 725647. Jump up ^ Histology image : 22501loa from Vaughan, Deborah ( 2002 ). A Learning System in Histology : CD - ROM and Guide. Oxford University Press. ISBN 978 - 0195151732. Jump up ^ Bergmann O, Bhardwaj RD, Bernard S, et al. ( April 2009 ). `` Evidence for cardiomyocyte renewal in humans ''. Science. 324 ( 5923 ) : 98 -- 102. PMC 2991140. PMID 19342590. doi : 10.1126 / science. 1164680. Jump up ^ Senyo SE, Steinhauser ML, Pizzimenti CL, Yang VK, Cai L, Wang M, Wu TD, Guerguin - Kern JL, Lechene CP, Lee RT ( January 2013 ). `` Mammalian heart renewal by pre-existing cardiomyocytes ''. Nature. 493 ( 7432 ) : 433 -- 6. PMC 3548046. PMID 23222518. doi : 10.1038 / nature11682. Jump up ^ Germani A, Di Rocco G, Limana F, Martelli F, Capogrossi MC ( March 2007 ). `` Molecular mechanisms of cardiomyocyte regenerate and therapeutic outlook ''. Trends Mol Med. 13 ( 3 ) : 125 -- 33. PMID 17257896. doi : 10.1016 / j. molmed. 2007.01. 002. Jump up ^ Orlic D, Kajstura J, Chimenti S, Jakoniuk I, Anderson SM, Li B, Pickel K, McKay R, Nadal - Ginard B, Bodine DM, Anversa P ( April 2001 ). `` Bone marrow cells regenerate infarcted myocardium ''. Nature. 410 ( 6829 ) : 701 -- 5. PMID 11287958. doi : 10.1038 / 35070587. Jump up ^ Orlic D, Hill JM, Arai AE ( December 2002 ). `` Stem cells for myocardial regeneration ''. Circ Res. 91 ( 12 ) : 1092 -- 102. PMID 12480809. doi : 10.1161 / 01. RES. 0000046045.00846. B0. External links Cardiac muscle histology Muscular system Tissue Muscle tissue Cardiac muscle Skeletal muscle Smooth muscle Fascia Superficial Deep Visceral Fascial compartment Tendon / Aponeurosis Shape Fusiform Pennate muscle Unipennate Bipennate Other Anatomical terms of muscle Origin Insertion List of muscles of the human body Composite muscle Muscle tissue Smooth muscle Calmodulin Vascular smooth muscle Striated muscle Skeletal muscle Costamere / DAPC Membrane / extracellular DAP : Sarcoglycan SGCA SGCB SGCD SGCE SGCG SGCZ Dystroglycan Sarcospan Laminin, alpha 2 Intracellular Dystrophin Dystrobrevin Syntrophin B1 B2 G1 G2 Syncoilin Dysbindin Synemin / desmuslin related : NOS1 Caveolin 3 Sarcomere / ( a, i, and h bands ; z and m lines ) Myofilament thin filament / actin thick filament / myosin elastic filament / titin nebulin Tropomyosin Troponin Connective tissue Epimysium Fascicle Perimysium Endomysium Connective tissue in skeletal muscle General Neuromuscular junction Motor unit Muscle spindle Excitation -- contraction coupling Sliding filament mechanism Cardiac muscle Myocardium Intercalated disc Nebulette Both Fiber Muscle fiber intrafusal extrafusal Myofibril Microfilament / Myofilament Sarcomere Cells Myoblast / Myocyte Myosatellite cell Other Desmin Sarcoplasm Sarcolemma T - tubule Sarcoplasmic reticulum Other / ungrouped Myotilin Telethonin Dysferlin Fukutin Fukutin - related protein Anatomy of the heart General Surface base apex sulci coronary interatrial anterior interventricular posterior interventricular borders right left Internal atria interatrial septum pectinate muscles terminal sulcus ventricles interventricular septum trabeculae carneae chordae tendineae papillary muscle valves cusps atrioventricular septum cardiac skeleton intervenous tubercle Chambers Right heart ( venae cavae, coronary sinus ) → right atrium ( atrial appendage, fossa ovalis, limbus of fossa ovalis, crista terminalis, valve of inferior vena cava, valve of coronary sinus ) → tricuspid valve → right ventricle ( infundibulum, moderator band / septomarginal trabecula ) → pulmonary valve → ( pulmonary artery and pulmonary circulation ) Left heart ( pulmonary veins ) → left atrium ( atrial appendage ) → mitral valve → left ventricle → aortic valve ( aortic sinus ) → ( aorta and systemic circulation ) Layers Endocardium heart valves Myocardium Conduction system cardiac pacemaker SA node Bachmann 's bundle AV node bundle of His bundle branches Purkinje fibers Pericardial cavity pericardial sinus Pericardium fibrous pericardium sternopericardial ligaments serous pericardium epicardium / visceral layer fold of Left vena cava Blood supply Circulatory system Coronary circulation Coronary arteries Retrieved from `` https://en.wikipedia.org/w/index.php?title=Cardiac_muscle&oldid=806431769 '' Categories : Cardiac anatomy Muscular system Cardiac electrophysiology Muscle tissue Histology Hidden categories : Wikipedia articles needing page number citations from April 2014 Articles containing video clips Talk Contents About Wikipedia Kiswahili 日本 語 Português Simple English Edit links This page was last edited on 22 October 2017, at 00 : 25. 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Question: where is cardiac muscle tissue located in the body
Answer: heart