CHAPTER 10 



Physiology of cardiac muscle 



ROBERT E. OLSON 



Department of Biochemistry and Nutrition, 

 University of Pittsburgh, Pittsburgh, Pennsylvania 



CHAPTER CONTENTS 



Structure of the Heart 



Anatomy 



Vasculature of Heart Muscle 



LUtrastructurc of Heart Muscle 



Myoglobin of Heart Muscle 



Lipids of the Myocardium 

 Pathways of Cardiac Metabolism 



Energy Liberation 



Energy Conservation 



Energy Utilization 

 Physiology of Substrate Utilization 

 Physiology of Substrate Extraction under Pathologic Conditions 



Hypoxia 



Shock 



Beriberi 



Diabetes Mellitus 



Hyperthyroidism 

 Pathologic Alteration in Contractile Proteins 



Primary Disease of Cardiac Muscle 



Secondary Disease of Cardiac Muscle 



FROM THE TIME of the discoveiv of the circulation of 

 the blood (95) to the present, the molecular events 

 underlying the motion of the heart have intrigued 

 biologic scientists. Although a large amount of in- 

 tensive research has been devoted to the elucidation 

 of these processes, it must be admitted that many 

 biochemical phenomena underlying contractility and 

 the adaptability of the heart muscle to varying work 

 loads are still visualized incompletely. It is clear, 

 however, that the ability of the heart to do work is 

 dependent upon the capacity of the enzyme systems 

 in cardiac muscle to convert chemical energy, avail- 

 able in \arious substrates, to mechanical work. Even 

 the shortening and lengthening of the m\ofibril in 

 the contractile cycle must lie \ie\ved in a biochemical 

 perspective. 



The function of the heart is to pump the blood at 

 a rate commensurate with the needs of the tissues. 

 The purpose of this chapter will be to review the 

 pertinent data drawn from many studies of ultra- 

 structure and cellular physiology which shed light 

 on the biochemical mechanisms underlving this es- 

 sential function. 



STRUCTURE OF THE HE.-^RT 



Anatomy 



The mammalian heart is a globular muscular organ 

 with four chambers and a fibrous skeleton composed 

 of four tendinous rings surrounding its four \alvular 

 orifices. The aortic ring is the strongest and is like 

 a cuff. The other rings are less rigid but firm enough 

 to prevent dilatation with valvular incompetence 

 during cardiac systole. The atrial musculature is 

 thin, translucent, and consists of only two layers 

 oriented at right angles to each other. The \entricular 

 muscle, contrastingly, is thick, opaque, and com- 

 posed of three layers: one superficial, one middle, 

 and one deep. The wall of the left ventricle is two 

 to three times as thick as that of the right \entricle 

 and constitutes the muscular foundation around 

 which the other chambers of the heart are built (136). 

 The thinner-walled right ventricle is fastened an- 

 teriorly and laterally, and may be described as a 

 crescentric pocket attached to the left ventricle. 

 Although the two ventricles are anatomically sepa- 

 rate, they function physically as an essentially common 

 musculature. The three layers of the ventricles are 

 formed by four major bundles of muscle fibers which 

 are /) the superficial sinospiral bundle; 2) the super- 

 ficial bulbospiral bundle; 3) the deep sinospiral 



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