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74 CHAPTER 19: THE CIRCULATORY SYSTEM: THE HEART Chapter Overview Introduction Heart disease continues to be our number one killer so the importance of understanding how the heart works is obvious. The anatomy of the heart is relatively simple with its 4 chambers, 4 valves, and several veins and arteries. However, the physiology of this muscular pump requires more consideration. Students will again see calcium ions being used as second messengers as with other types of muscle tissue but there are certain key differences as the text makes clear. Dr. Saladin discusses various cardiac parameters (e.g., pressure, flow) and their importance. The importance of the various controls over heart rhythm and contract force (i.e., cardiac output) is significant: the cardiac conduction system, nerves, hormones, and end- diastolic volume. The author also looks into the progression of coronary artery disease. Key Concepts Here are some concepts that students should have a better understanding of after reading this chapter: basic anatomy of the heart, surrounding tissues, and the coronary circulation; the roles of all four valves in ensuring proper blood flow direction; the blood supply and perfusion of the myocardium and the relationship between ischemia and infarction; structures, functions, and metabolism of cardiac muscle cells distinguishing it from skeletal muscle; the means and structures of message conduction within the heart and the coordination of contraction; cardiac rhythm and the physiology of the sinoatrial node; the electrocardiogram and its interpretation; concepts of pressure and flow; the pattern of flow of blood through the heart, actions of the valves and chambers in relation to the phases of the cardiac cycle; the causes of heart sounds; volume changes throughout the cardiac cycle; changes in cardiac output, the factors affecting cardiac output, and the methods of controlling these changes; effects of certain chemicals, such as caffeine, and electrolytes on heart rate; the Frank-Starling law of the heart, stroke volume, preload, and contractility; and the elements leading to arteriosclerosis and the treatment of coronary heart disease. Topics for Discussion 1. Have some of the students obtain recent data from the National Institutes of Health or the Centers for Disease Control about the number of people who died in the previous year of heart disease. For the past several years this has been about 45% of all deaths in the United States or around 1,000,000 annually, more than all cancers, HIV, and auto accidents combined. 2. The best way to stop heart attacks is through prevention. Have students research the literature to find ways to prevent heart attacks in themselves. At the same time, everyone can make a diary for a week of their diet with attention to diet and exercise that affect LDL and HDL levels. Some mention of smoking habits might be appropriate here since it is an important contributor to cardiovascular disease. 3.
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