Setting Up Wholly Foreign Owned Enterprises in China
Do you want to manufacture or trade in China? If you are looking at investing in a China manufacturing or service operation in China, then this book is for you. This Guide is a practical overview for the international businessman to understand the rules,
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The Cardiac Conduction System Timothy G. Laske, Maneesh Shrivastav, and Paul A. Iaizzo
Abstract The intrinsic conduction system of the heart is comprised of several specialized subpopulations of cells that either spontaneously generate electrical activity (pacemaker cells) or preferentially conduct this activity throughout the chambers in a coordinated fashion. This chapter will discuss the details of this known anatomy as well as put such discoveries into a historical context. The cardiac action potential underlies signaling within the heart and the various populations of myocytes will elicit signature waveforms. The recording or active sensing of these potentials is important in both research and clinical arenas. This chapter aims to provide a basic understanding of the cardiac conduction system to provide the reader with a foundation for future research and reading on this topic. The information in this chapter is not comprehensive and should not be used to make decisions relating to patient care. Keywords Cardiac conduction Sinoatrial node Depolarization Atrioventricular node Electrophysiology Cardiac action potential Gap junction
11.1 Introduction Orderly contractions of the atria and ventricles are regulated by the transmission of electrical impulses that pass through an intricate network of modified cardiac muscle cells, ‘‘the cardiac conduction system.’’ These cells are interposed within the contractile myocardium. This intrinsic conduction system is comprised of several specialized subpopulations of cells that spontaneously generate electrical activity (pacemaker cells) and/or preferentially conduct this activity throughout the heart. Following an initiating activation (or depolarization) within the T.G. Laske (*) University of Minnesota, Department of Surgery, and Medtronic, Inc., 8200 Coral Sea St. NE, MVS84, Mounds view, MN 55112, USA e-mail: [email protected]
myocardium, this electrical excitation spreads throughout the heart in a rapid and highly coordinated fashion. This system of cells also functionally controls the timing of the transfer of activity between the atrial and ventricular chambers. Interestingly, a common global architecture is present in mammals, but significant interspecies differences exist at the histologic level [1, 2] (see also Chapter 6). Discoveries relating to this intrinsic conduction system within the heart are relatively recent relative to cardiac function and anatomy. Johannes E. von Purkinje first described the ventricular conduction system in 1845 and Gaskell, an electrophysiologist, coined the phrase ‘‘heart block’’ in 1882. Importantly, Gaskell also related the presence of a slow ventricular rate to disassociation with the atria [3]. The discovery of the mammalian sinoatrial node was published by Sir Arthur Keith and Martin Flack in 1907 in the Journal of Anatomy and Physiology. Nevertheless, novel findings relating to the functionality of this node are still being made today [4]. The elucidation of the bundle of His is attributed to its namesake,
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