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Unformatted text preview: Lecture summary: see Power Point file for illustrations. Loegering Rhoades & Tanner p. 252-256; 271-274 290-292; 298-301 Systemic Circulation Learning Objectives The three most important learning objectives of this lecture are: 1. Metabolic control of blood flow. a. This is an intrinsic type of blood flow control. b. Active hyperemia is an example of the metabolic control of blood flow. c. Understand the role of vasodilator metabolites in the metabolic control of blood flow. d. Explain how changes in the metabolic rate of a tissue alter the vascular resistance in that tissue. 2. Myogenic control of blood flow . a. This is an intrinsic type of blood flow control. b. Autoregulation is an example of the myogenic control of blood flow. c. Understand the role of stretch of vascular smooth muscle in the myogenic control of blood flow. d. Explain how changes in arterial pressure cause the myogenic control of blood flow. e. Describe the role of vasodilating metabolites in autoregulation f. Define basal tone and distinguish it from neural tone. 3. Neural control of blood flow. a. This is an extrinsic type of blood flow control. b. Sympathetic activity is primarily responsible for neural control of the systemic circulation. c. Describe how changes in sympathetic activity can cause an increase or decrease in vascular resistance. d. Define neural tone. Other learning objectives of the lecture are: 1. List the determinants of the mean arterial pressure. 2. Be able to calculate the mean arterial pressure when given the systolic and diastolic pressures. 3. Formulate the relationship between pulse pressure, stroke volume and the compliance of the arterial system. 4. Describe the effects of gravity on the cardiovascular system. 5. Explain how the respiratory pump works. 6. Explain how the skeletal muscle pump works. 7. Describe the effects of changes in venous compliance on central venous pressure. 8. List 4 humoral agents that can affect the systemic circulation. The systemic circulation includes all the blood vessels that originate at the left ventricle and terminate at the right atrium. This lecture will include a description of some of the characteristics of the systemic arteries, the systemic veins, and the control of blood flow in the systemic circulation. Systemic arteries : As you know from the lecture on hemodynamics, blood flow (F) is equal to the pressure difference ( P) divided by the resistance (R): F = P/R. For the entire systemic circulation, F is the cardiac output (CO), P is the mean arterial pressure (MAP) minus the right atrial pressure, and R is the systemic vascular resistance (SVR) which is also known as total peripheral resistance. MAP is often used as P because right atrial pressure normally is just a few mm Hg. For this situation, P or MAP may be referred to as the perfusion pressure. If we rewrite the original equation as P = F x R, we arrive at the commonly used expression: MAP = CO x SVR. Now we can see that variations in both cardiac output and systemic vascular...
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- Spring '08