Cardiovascular Physiology Notice Medicine is an ever-changing science As new research and clinical experience broaden our knowledge, changes in treatment and drug therapy are required The authors and the publisher of this work have checked with sources believed to be reliable in their efforts to provide information that is complete and generally in accord with the standards accepted at the time of publication However, in view of the possibility of human error or changes in medical sciences, neither the authors nor the publisher nor any other party who has been involved in the preparation or publication of this work warrants that the information contained herein is in every respect accurate or complete, and they disclaim all responsibility for any errors or omissions or for the results obtained from use of the information contained in this work Readers are encouraged to confirm the information contained herein with other sources For example and in particular, readers are advised to check the product information sheet included in the package of each drug they plan to administer to be certain that the information contained in this work is accurate and that changes have not been made in the recommended dose or in the contraindications for administration This recommendation is of particular importance in connection with new or infrequently used drugs a LANGE medical book Cardiovascular Physiology 7th edition David E Mohrman, PhD Associate Professor Department of Physiology and Pharmacology University of Minnesota Medical School Duluth, Minnesota Lois Jane Heller, PhD Professor Department of Physiology and Pharmacology University of Minnesota Medical School Duluth, Minnesota Copyright © 2010, 2006, 2003, 1997, 1991, 1986, 1981 by The McGraw-Hill Companies, Inc All rights reserved Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or 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these terms Except as permitted under the Copyright Act of 1976 and the right to store and retrieve one copy of the work, you may not decompile, disassemble, reverse engineer, reproduce, modify, create derivative works based upon, transmit, distribute, disseminate, sell, publish or sublicense the work or any part of it without McGraw-Hill’s prior consent You may use the work for your own noncommercial and personal use; any other use of the work is strictly prohibited Your right to use the work may be terminated if you fail to comply with these terms THE WORK IS PROVIDED “AS IS.” McGRAW-HILL AND ITS LICENSORS MAKE NO GUARANTEES OR WARRANTIES AS TO THE ACCURACY, ADEQUACY OR COMPLETENESS OF OR RESULTS TO BE OBTAINED FROM USING THE WORK, INCLUDING ANY INFORMATION THAT CAN BE ACCESSED THROUGH THE WORK VIA HYPERLINK OR OTHERWISE, AND EXPRESSLY DISCLAIM ANY WARRANTY, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE McGraw-Hill and its licensors not warrant or guarantee that the functions contained in the work will meet your requirements or that its operation will be uninterrupted or error free Neither McGraw-Hill nor its licensors shall be liable to you or anyone else for any inaccuracy, error or omission, regardless of cause, in the work or for any damages resulting there from McGraw-Hill has no responsibility for the content of any information accessed through the work Under no circumstances shall McGraw-Hill and/or its licensors be liable for any indirect, incidental, special, punitive, consequential or similar damages that result from the use of or inability to use the work, even if any of them has been advised of the possibility of such damages This limitation of liability shall apply to any claim or cause whatsoever whether such claim or cause arises in contract, tort or otherwise Contents Preface Chapter Overview of the Cardiovascular System Objectives Homeostatic Role of the Cardiovascular System The Basic Physics of Blood Flow The Heart The Vasculature Blood Foundation for Subsequent Chapters Key Concepts Study Questions Chapter Characteristics of Cardiac Muscle Cells Objectives Electrical Activity of Cardiac Muscle Cells Mechanical Activity of the Heart Relating Cardiac Muscle Cell Mechanics to Ventricular Function Key Concepts Study Questions Chapter The Heart Pump Objectives Cardiac Cycle Determinants of Cardiac Output Influences on Stroke Volume Summary of Determinants of Cardiac Output Cardiac Energetics Key Concepts Study Questions Chapter Measurements of Cardiac Function Objectives Measurement of Cardiac Output Cardiac Contractility Estimates Measurement of Cardiac Excitation—The Electrocardiogram Cardiac Dipoles and Electrocardiographic Records Mean Electrical Axis and Axis Deviations The Standard 12-Lead Electrocardiogram Key Concepts Study Questions Chapter Cardiac Abnormalities Objectives Electrical Abnormalities and Arrhythmias Valvular Abnormalities Key Concepts Study Questions Chapter The Peripheral Vascular System Objectives Cardiovascular Transport Basic Vascular Function Measurement of Arterial Pressure Determinants of Arterial Pressure Key Concepts Study Questions Chapter Vascular Control Objectives Vascular Smooth Muscle Control of Arteriolar Tone Control of Venous Tone Summary of Primary Vascular Control Mechanisms Vascular Control of Coronary Blood Flow Vascular Control in Specific Organs Key Concepts Study Questions Chapter Central Venous Pressure: An Indicator of Circulatory Hemodynamics Objectives Interaction of System Components Central Venous Pressure: An Indicator of Circulatory Status Influence of Central Venous Pressure on Venous Return Influence of Peripheral Venous Pressure on Venous Return Determination of Cardiac Output and Venous Return by Central Venous Pressure Clinical Implications of Abnormal Central Venous Pressures Key Concepts Study Questions Chapter Regulation of Arterial Pressure Objectives Short-Term Regulation of Arterial Pressure Long-Term Regulation of Arterial Pressure Key Concepts Study Questions Chapter 10 Cardiovascular Responses to Physiological Stresses Objectives Effect of Respiratory Activity Effect of Gravity Effect of Exercise Normal Cardiovascular Adaptations Effect of Gender Key Concepts Study Questions Chapter 11 Cardiovascular Function in Pathological Situations Objectives Circulatory Shock Cardiac Disturbances Hypertension Key Concepts Study Questions Answers to Study Questions Appendix A Appendix B Appendix C Appendix D Appendix E Index Although the respiratory effects of right heart filling are emphasized in Figure 10–1, respiration also directly affects left heart filling However, the events are somewhat different because both the left atria and the whole of the pulmonary vascular system are affected by changes in intrathoracic pressure There are also some time delays between changes in right heart filling and left ventricular stroke volume that are ignored in Figure 10–1 The specific phase relationships between the respiratory cycle and the cardiovascular effects are influenced by respiratory rate and depth as well as the current average heart rate Much of the benefit of exercise “conditioning” can be attributed to the increase in circulating blood volume This process represents the opposite end of a functional spectrum from the “deconditioning” effects of long-term bed rest that decreases circulating blood volume However, as described in the next chapter, ventricular chamber enlargement and myocardial hypertrophy are not always hallmarks of improved cardiac performance but may be adaptive responses to various pathological states that, if extreme, may not be helpful In the case of cardiogenic shock, central venous pressure will increase; and in the case of neurogenic shock, central venous pressure cannot be predicted because both cardiac output and venous return are likely to be depressed Thus, in these instances, it is not clear how the cardiopulmonary baroreceptors affect autonomic output Two primary exceptions to this statement include (1) neurogenic shock, where reflex responses may be absent or lead to further depression of blood pressure, and (2) certain instances of cardiogenic shock associated with inferoposterior myocardial infarctions, which elicit a reflex bradycardia and decrease sympathetic drive (the Bezold–Jarisch reflex) Another method for treatment of acute myocardial infarction has been the intravascular injection of thrombolytic substances (eg, streptokinase or tissue plasminogen-activating factors) that dissolve blood clots This method is most successful when these clot busters are given within a few hours of the infarction The extracellular fluid volume remains expanded after reaching the compensated state even though sympathetic activity may have returned to near normal levels Net fluid loss requires a period of less than normal sympathetic activity, which does not occur For reasons not well understood, the cardiopulmonary baroreceptor reflexes apparently become less responsive to the increased central venous pressure and volume associated with heart failure Patients often complain of difficulty breathing especially during the night (paroxysmal nocturnal dyspnea) Being recumbent promotes a fluid shift from the extremities into the central venous pool and lungs, making the patient’s pulmonary problems worse Such patients often sleep more comfortably when propped up Plasma volume expansion combines with abnormal liver function to reduce the concentration of plasma proteins by as much as 30% This reduction in plasma oncotic pressure contributes to the development of interstitial edema of congestive heart failure A “tea” made from the leaves of the foxglove plant (Digitalis purpurea) was used for centuries as a common folk remedy for the treatment of “dropsy” (congestive heart failure with significant peripheral edema) With the formal recognition of its medicinal benefits in the late-18th century by the English physician Sir William Withering, digitalis became a valuable official pharmacological tool The mechanism of cardiac glycoside action is thought to involve the inhibition of the sodium/potassium adenosine triphosphatase (Na+/K+ATPase) leading to increases in intracellular [Na+], which is then exchanged for extracellular calcium via the Na+/Ca2+ exchanger This results in “loading” of the sarcoplasmic reticulum during diastole and increased calcium release for subsequent excitation–contraction coupling The ACE inhibitors are very helpful to the congestive heart failure patient for several reasons By inhibiting the conversion of angiotensin I into its more active form, angiotensin II, peripheral vasoconstriction is reduced (which improves cardiac pumping by afterload reduction) and aldosterone levels are reduced (which promotes diuresis) In addition, ACE inhibitors as well as the ARBs seem to prevent some of the apparently inappropriate myocyte and collagen growth (ie, remodeling) that occurs with cardiac overload and failure 10 It is noteworthy that acute pulmonary hypertension and pulmonary edema are recognized risks of mountain climbing to extreme altitudes without the aid of supplemental oxygen 11 Because an increased risk of cardiovascular complications with even mildly elevated blood pressure has been identified, a category designated prehypertension has been added to include blood pressures ranging from 120 to 139 mmHg systolic and 80 to 89 mmHg diastolic 12 Continuous activation of vascular smooth muscle might be evoked by autoregulatory responses to increased blood pressure, as discussed in Chapter A total body autoregulation could produce an increase in total peripheral resistance so that total systemic flow (ie, cardiac output) would remain nearly normal in the presence of increased mean arterial pressure ... goal is to have students “understand” rather than “know” cardiovascular physiology We are also conscious of the fact that cardiovascular physiology is allotted less and less time in most curricula... or infrequently used drugs a LANGE medical book Cardiovascular Physiology 7th edition David E Mohrman, PhD Associate Professor Department of Physiology and Pharmacology University of Minnesota... Jane Heller, PhD Overview of the Cardiovascular System OBJECTIVES The student understands the homeostatic role of the cardiovascular system, the basic principles of cardiovascular transport, and