{"id":1995,"date":"2014-10-27T21:16:07","date_gmt":"2014-10-27T21:16:07","guid":{"rendered":"https:\/\/courses.candelalearning.com\/apvccs\/?post_type=chapter&#038;p=1995"},"modified":"2016-10-20T15:42:28","modified_gmt":"2016-10-20T15:42:28","slug":"cardiac-muscle-tissue","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-mcc-ap1\/chapter\/cardiac-muscle-tissue\/","title":{"raw":"Cardiac Muscle Tissue","rendered":"Cardiac Muscle Tissue"},"content":{"raw":"<div>\r\n<div class=\"bcc-box bcc-highlight\">\r\n<h3>Learning Objectives<\/h3>\r\n<div>\r\n<div>\r\n<ul>\r\n \t<li>Describe intercalated discs and gap junctions<\/li>\r\n \t<li>Describe a desmosome<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\nCardiac muscle tissue is only found in the heart. Highly coordinated contractions of cardiac muscle pump blood into the vessels of the circulatory system. Similar to skeletal muscle, cardiac muscle is striated and organized into sarcomeres, possessing the same banding organization as skeletal muscle (Figure\u00a010.21). However, cardiac muscle fibers are shorter than skeletal muscle fibers and usually contain only one nucleus, which is located in the central region of the cell. Cardiac muscle fibers also possess many mitochondria and myoglobin, as ATP is produced primarily through aerobic metabolism. Cardiac muscle fibers cells also are extensively branched and are connected to one another at their ends by intercalated discs. An<strong>\u00a0<em>intercalated disc<\/em><\/strong><a id=\"id702802\"><\/a>\u00a0allows the cardiac muscle cells to contract in a wave-like pattern so that the heart can work as a pump.\r\n<div id=\"m46404-fig-ch10_07_01\" title=\"Figure\u00a010.21.\u00a0Cardiac Muscle Tissue\">\r\n<div>\r\n<div><img src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/18\/2014\/07\/19181641\/414c_Cardiacmuscle.jpg\" alt=\"This image is a micrograph of cardiac muscle cells.\" width=\"380\" \/><\/div>\r\n<\/div>\r\n<address><strong>Figure\u00a010.21.\u00a0Cardiac Muscle Tissue<\/strong><\/address><address>Cardiac muscle tissue is only found in the heart. LM \u00d7 1600. (Micrograph provided by the Regents of University of Michigan Medical School \u00a9 2012)<\/address><address>\u00a0<\/address><\/div>\r\n<div id=\"m46404-fs-id2327137\">\r\n<div><\/div>\r\n<div>\r\n<div class=\"bcc-box bcc-info\">\r\n<h3>Interactive Link<\/h3>\r\n<div id=\"m46404-fs-id2327137\">\r\n<div>\r\n\r\nView the University of Michigan WebScope at<a href=\"http:\/\/openstaxcollege.org\/l\/cardmuscleMG\" target=\"_blank\">http:\/\/virtualslides.med.umich.edu\/Histology\/Cardiovascular%20System\/305_HISTO_40X.svs\/view.apml<\/a>\u00a0to explore the tissue sample in greater detail.\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<span style=\"line-height: 1.5em;\">Intercalated discs are part of the sarcolemma and contain two structures important in cardiac muscle contraction: gap junctions and desmosomes. A gap junction forms channels between adjacent cardiac muscle fibers that allow the depolarizing current produced by cations to flow from one cardiac muscle cell to the next. This joining is called electric coupling, and in cardiac muscle it allows the quick transmission of action potentials and the coordinated contraction of the entire heart. This network of electrically connected cardiac muscle cells creates a functional unit of contraction called a syncytium. The remainder of the intercalated disc is composed of desmosomes. A\u00a0<\/span><em style=\"line-height: 1.5em;\">desmosome<\/em><a id=\"id702915\" style=\"line-height: 1.5em; background-color: #ffffff;\"><\/a><span style=\"line-height: 1.5em;\">\u00a0is a cell structure that anchors the ends of cardiac muscle fibers together so the cells do not pull apart during the stress of individual fibers contracting (<\/span>Figure\u00a010.22<span style=\"line-height: 1.5em;\">).<\/span>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"m46404-fig-ch10_07_02\" title=\"Figure\u00a010.22.\u00a0Cardiac Muscle\">\r\n<div>\r\n<div><img src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/18\/2014\/07\/19181644\/1020_Cardiac_Muscle.jpg\" alt=\"This image shows the structure of the cardiac muscle. A small image of the heart is shown on the top left of the figure and then a magnified view of the cardiac muscle is shown, with the nucleus and the cardiac muscle fiber labeled. A further magnification shows the structure of the intercalated discs with the desmosome and gap junction.\" width=\"480\" \/><\/div>\r\n<\/div>\r\n<address><strong>Figure\u00a010.22.\u00a0Cardiac Muscle<\/strong><\/address><address>Intercalated discs are part of the cardiac muscle sarcolemma and they contain gap junctions and desmosomes.<\/address><address>\u00a0<\/address><\/div>\r\nContractions of the heart (heartbeats) are controlled by specialized cardiac muscle cells called pacemaker cells that directly control heart rate. Although cardiac muscle cannot be consciously controlled, the pacemaker cells respond to signals from the autonomic nervous system (ANS) to speed up or slow down the heart rate. The pacemaker cells can also respond to various hormones that modulate heart rate to control blood pressure.\r\n\r\nThe wave of contraction that allows the heart to work as a unit, called a functional syncytium, begins with the pacemaker cells. This group of cells is self-excitable and able to depolarize to threshold and fire action potentials on their own, a feature called\u00a0<strong><em>autorhythmicity<\/em><\/strong><a id=\"id702990\"><\/a>; they do this at set intervals which determine heart rate. Because they are connected with gap junctions to surrounding muscle fibers and the specialized fibers of the heart\u2019s conduction system, the pacemaker cells are able to transfer the depolarization to the other cardiac muscle fibers in a manner that allows the heart to contract in a coordinated manner.\r\n\r\nAnother feature of cardiac muscle is its relatively long action potentials in its fibers, having a sustained depolarization \u201cplateau.\u201d The plateau is produced by Ca<sup>++<\/sup>\u00a0entry though voltage-gated calcium channels in the sarcolemma of cardiac muscle fibers. This sustained depolarization (and Ca<sup>++<\/sup>\u00a0entry) provides for a longer contraction than is produced by an action potential in skeletal muscle. Unlike skeletal muscle, a large percentage of the Ca<sup>++<\/sup>\u00a0that initiates contraction in cardiac muscles comes from outside the cell rather than from the SR.","rendered":"<div>\n<div class=\"bcc-box bcc-highlight\">\n<h3>Learning Objectives<\/h3>\n<div>\n<div>\n<ul>\n<li>Describe intercalated discs and gap junctions<\/li>\n<li>Describe a desmosome<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<p>Cardiac muscle tissue is only found in the heart. Highly coordinated contractions of cardiac muscle pump blood into the vessels of the circulatory system. Similar to skeletal muscle, cardiac muscle is striated and organized into sarcomeres, possessing the same banding organization as skeletal muscle (Figure\u00a010.21). However, cardiac muscle fibers are shorter than skeletal muscle fibers and usually contain only one nucleus, which is located in the central region of the cell. Cardiac muscle fibers also possess many mitochondria and myoglobin, as ATP is produced primarily through aerobic metabolism. Cardiac muscle fibers cells also are extensively branched and are connected to one another at their ends by intercalated discs. An<strong>\u00a0<em>intercalated disc<\/em><\/strong><a id=\"id702802\"><\/a>\u00a0allows the cardiac muscle cells to contract in a wave-like pattern so that the heart can work as a pump.<\/p>\n<div id=\"m46404-fig-ch10_07_01\" title=\"Figure\u00a010.21.\u00a0Cardiac Muscle Tissue\">\n<div>\n<div><img decoding=\"async\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/18\/2014\/07\/19181641\/414c_Cardiacmuscle.jpg\" alt=\"This image is a micrograph of cardiac muscle cells.\" width=\"380\" \/><\/div>\n<\/div>\n<address><strong>Figure\u00a010.21.\u00a0Cardiac Muscle Tissue<\/strong><\/address>\n<address>Cardiac muscle tissue is only found in the heart. LM \u00d7 1600. (Micrograph provided by the Regents of University of Michigan Medical School \u00a9 2012)<\/address>\n<address>\u00a0<\/address>\n<\/div>\n<div id=\"m46404-fs-id2327137\">\n<div><\/div>\n<div>\n<div class=\"bcc-box bcc-info\">\n<h3>Interactive Link<\/h3>\n<div id=\"m46404-fs-id2327137\">\n<div>\n<p>View the University of Michigan WebScope at<a href=\"http:\/\/openstaxcollege.org\/l\/cardmuscleMG\" target=\"_blank\">http:\/\/virtualslides.med.umich.edu\/Histology\/Cardiovascular%20System\/305_HISTO_40X.svs\/view.apml<\/a>\u00a0to explore the tissue sample in greater detail.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<p><span style=\"line-height: 1.5em;\">Intercalated discs are part of the sarcolemma and contain two structures important in cardiac muscle contraction: gap junctions and desmosomes. A gap junction forms channels between adjacent cardiac muscle fibers that allow the depolarizing current produced by cations to flow from one cardiac muscle cell to the next. This joining is called electric coupling, and in cardiac muscle it allows the quick transmission of action potentials and the coordinated contraction of the entire heart. This network of electrically connected cardiac muscle cells creates a functional unit of contraction called a syncytium. The remainder of the intercalated disc is composed of desmosomes. A\u00a0<\/span><em style=\"line-height: 1.5em;\">desmosome<\/em><a id=\"id702915\" style=\"line-height: 1.5em; background-color: #ffffff;\"><\/a><span style=\"line-height: 1.5em;\">\u00a0is a cell structure that anchors the ends of cardiac muscle fibers together so the cells do not pull apart during the stress of individual fibers contracting (<\/span>Figure\u00a010.22<span style=\"line-height: 1.5em;\">).<\/span><\/p>\n<\/div>\n<\/div>\n<div id=\"m46404-fig-ch10_07_02\" title=\"Figure\u00a010.22.\u00a0Cardiac Muscle\">\n<div>\n<div><img decoding=\"async\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/18\/2014\/07\/19181644\/1020_Cardiac_Muscle.jpg\" alt=\"This image shows the structure of the cardiac muscle. A small image of the heart is shown on the top left of the figure and then a magnified view of the cardiac muscle is shown, with the nucleus and the cardiac muscle fiber labeled. A further magnification shows the structure of the intercalated discs with the desmosome and gap junction.\" width=\"480\" \/><\/div>\n<\/div>\n<address><strong>Figure\u00a010.22.\u00a0Cardiac Muscle<\/strong><\/address>\n<address>Intercalated discs are part of the cardiac muscle sarcolemma and they contain gap junctions and desmosomes.<\/address>\n<address>\u00a0<\/address>\n<\/div>\n<p>Contractions of the heart (heartbeats) are controlled by specialized cardiac muscle cells called pacemaker cells that directly control heart rate. Although cardiac muscle cannot be consciously controlled, the pacemaker cells respond to signals from the autonomic nervous system (ANS) to speed up or slow down the heart rate. The pacemaker cells can also respond to various hormones that modulate heart rate to control blood pressure.<\/p>\n<p>The wave of contraction that allows the heart to work as a unit, called a functional syncytium, begins with the pacemaker cells. This group of cells is self-excitable and able to depolarize to threshold and fire action potentials on their own, a feature called\u00a0<strong><em>autorhythmicity<\/em><\/strong><a id=\"id702990\"><\/a>; they do this at set intervals which determine heart rate. Because they are connected with gap junctions to surrounding muscle fibers and the specialized fibers of the heart\u2019s conduction system, the pacemaker cells are able to transfer the depolarization to the other cardiac muscle fibers in a manner that allows the heart to contract in a coordinated manner.<\/p>\n<p>Another feature of cardiac muscle is its relatively long action potentials in its fibers, having a sustained depolarization \u201cplateau.\u201d The plateau is produced by Ca<sup>++<\/sup>\u00a0entry though voltage-gated calcium channels in the sarcolemma of cardiac muscle fibers. This sustained depolarization (and Ca<sup>++<\/sup>\u00a0entry) provides for a longer contraction than is produced by an action potential in skeletal muscle. Unlike skeletal muscle, a large percentage of the Ca<sup>++<\/sup>\u00a0that initiates contraction in cardiac muscles comes from outside the cell rather than from the SR.<\/p>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-1995\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Chapter 10. <strong>Authored by<\/strong>: OpenStax College. <strong>Provided by<\/strong>: Rice University. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/cnx.org\/contents\/14fb4ad7-39a1-4eee-ab6e-3ef2482e3e22@7.1@7.1.\">http:\/\/cnx.org\/contents\/14fb4ad7-39a1-4eee-ab6e-3ef2482e3e22@7.1@7.1.<\/a>. <strong>Project<\/strong>: Anatomy &amp; Physiology. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em>. <strong>License Terms<\/strong>: Download for free at http:\/\/cnx.org\/content\/col11496\/latest\/. <\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":74,"menu_order":8,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Chapter 10\",\"author\":\"OpenStax College\",\"organization\":\"Rice University\",\"url\":\"http:\/\/cnx.org\/contents\/14fb4ad7-39a1-4eee-ab6e-3ef2482e3e22@7.1@7.1.\",\"project\":\"Anatomy & Physiology\",\"license\":\"cc-by\",\"license_terms\":\"Download for free at http:\/\/cnx.org\/content\/col11496\/latest\/. \"}]","CANDELA_OUTCOMES_GUID":"","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-1995","chapter","type-chapter","status-publish","hentry"],"part":1978,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-ap1\/wp-json\/pressbooks\/v2\/chapters\/1995","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-ap1\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-ap1\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-ap1\/wp-json\/wp\/v2\/users\/74"}],"version-history":[{"count":3,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-ap1\/wp-json\/pressbooks\/v2\/chapters\/1995\/revisions"}],"predecessor-version":[{"id":3085,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-ap1\/wp-json\/pressbooks\/v2\/chapters\/1995\/revisions\/3085"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-ap1\/wp-json\/pressbooks\/v2\/parts\/1978"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-ap1\/wp-json\/pressbooks\/v2\/chapters\/1995\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-ap1\/wp-json\/wp\/v2\/media?parent=1995"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-ap1\/wp-json\/pressbooks\/v2\/chapter-type?post=1995"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-ap1\/wp-json\/wp\/v2\/contributor?post=1995"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-ap1\/wp-json\/wp\/v2\/license?post=1995"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}