The Contractile Apparatus of the Heart
In the present chapter, I will describe basic structural and functional features of the contractile apparatus of muscle cells of the heart, namely, cardiomyocytes and smooth muscle cells. Cardiomyocytes form the contractile myocardium of the heart, while
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The Contractile Apparatus of the Heart Ingo Morano
Contents 17.1 17.2 17.3 17.4 17.5
Introduction The Myocardium The Myosin Filament The Actin Filament Cardiomyocyte Contraction 17.5.1 Isometric Contraction 17.5.2 Isotonic Contraction 17.6 Excitation-Contraction Coupling of Cardiomyocytes 17.7 Smooth Muscle Cells of Coronary Vessels 17.8 Excitation-Contraction Coupling of Mammalian Smooth Muscle Conclusion References
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Abstract
In the present chapter, I will describe basic structural and functional features of the contractile apparatus of muscle cells of the heart, namely, cardiomyocytes and smooth muscle cells. Cardiomyocytes form the contractile myocardium of the heart, while smooth muscle cells form the contractile coronary vessels. Both muscle types have distinct properties and will be considered with respect to their cellular appearance (brick-like cross-striated versus spindle-like smooth), arrangement of contractile proteins (organized in sarcomeres versus non- sarcomeric organization), calcium activation mechanisms (thin-filament versus thick-filament regulation), contractile features (fast and phasic versus slow and
I. Morano Department of Molecular Muscle Physiology, Max-Delbrück Center for Molecular Medicine and University Medicine Charité Berlin, Berlin, Germany e-mail: [email protected] © Springer-Verlag Wien 2016 S. Rickert-Sperling et al. (eds.), Congenital Heart Diseases: The Broken Heart: Clinical Features, Human Genetics and Molecular Pathways, DOI 10.1007/978-3-7091-1883-2_17
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tonic), energy metabolism (high oxygen versus low oxygen demand), chemomechanical energy conversion (high adenosine triphosphate (ATP) consumption and short duty ratio versus low ATP consumption and high duty ratio), excitation- contraction coupling (calcium-induced calcium release versus pharmacomechanical coupling), and molecular motors (type II myosin isoenzymes with high adenosine diphosphate (ADP)-release rate versus myosin isoenzymes with low ADP-release rates).
17.1 Introduction Part of the work has been published in Chap. 22 [1] in “Neuroscience – From Molecules to Behavior” (Galizia and Lledo eds 2013), Springer-Verlag (with kind permission from Springer Science + Business Media). The heart is a permanently contractile organ. Each day, the human heart contracts approximately 86,000 times, pumping about 3,500–4,500 l of blood through the body and performing about 100 kJ of work. The tone of coronary vessels regulates the perfusion of the heart with blood [2].
17.2 The Myocardium The heart consists of the epicardium, which covers the outer surface, and the endocardium, which covers the inner surfaces, with the myocardium in between. The myocardium consists of sheets of contractile cells, the cardiomyocytes, which are interconnected by electron-dense specialized cell-cell junctions, the intercalated disks, providing mechanical stability and electrical communication between neighboring cardiomyocyt
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