The coronary circulation provides blood flow to the heart. During resting conditions, the heart muscle consumes about as much oxygen as does an equal mass of skeletal muscle during vigorous exercise (see Table 17.1). Coronary blood flow can normally increase about 4- to 5-fold, to provide more of the heart's oxygen needs, during heavy exercise. This increment in blood flow constitutes the coronary blood flow reserve. The ability to increase the blood flow to provide additional oxygen is imperative. Heart tissue extracts almost the maximum amount of oxygen from blood during resting conditions. Because the heart's ability to use anaerobic glycolysis to provide energy is limited, the only practical way to increase energy production is to increase blood flow and oxygen delivery. The production of lactic acid by the heart is an ominous sign of grossly inadequate oxygenation.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.