Content Display. - Introduction to Unit 4. Unit 4 - Cardiorespiratory Response to Exercise : Lesson 1. KINE xxxx Exercise Physiology

Transcription

1 Content Display Unit 4 - Cardiorespiratory Response to Exercise : Lesson KINE xxxx Exercise Physiology 5 Unit 4 - Cardiorespiratory Response to Exercise Lesson U4LP - Introduction to Unit 4 The specific topic of Unit 4 is cardiorespiratory response to exercise. This will be presented in three lessons. In this first lesson, in addition to introducing and giving an overview of the Unit, I will address concepts that apply to the more general topic of cardiorespiratory exercise physiology. Then I will focus on respiration in Lesson 2 and on cardiovascular physiology in Lesson 3. The approach in this unit will be a little different from the approach taken in Units -3. I will present less topical content ( lecture material ) online in this unit, compared with previous units (especially Units 2 and 3). Instead, I will try to highlight major concepts in a more summary fashion. Thus, you will find fewer online pages in this unit than in the previous ones. The tradeoff is that you will have to rely more on the textbook. We will continue to use WebBoard discussions; perhaps the contents of these may have to be changed a little to better complement the difference in presentation of content in this unit. Contents of Lesson : Description Page Introduction to Unit 4 - Lesson -5 Cardiorespiratory Exercise Physiology 6 Glossary of Selected Terms and Abbreviations 7-8 The Fick Equation 9- Summary Introduction of Cardiorespiratory Variables Related to VO2 2 2 U4LP2 of 3 5/7/200 3:50 PM

2 - Introduction to Unit 4 Assignments. Read, study and master the content presented online in Lessons Read and study in the textbook: Chapter 9, Circulatory Adaptations to Exercise (omit details about electrocardiograms in Figure 9.8-0) Chapter 0, Respiration during Exercise Chapter, Acid-Base Balance during Exercise (read and study as overview only, unless specific topics are addressed in online lessons) Related sections of Chapter 3, The Physiology of Training etc. (for this unit, focus on the parts of the chapter related to cardiorespiratory physiology) You may also want to check key terms in the textbook index; sometimes topics are addressed in several places throughout a textbook. 3. Participate in conference discussions on WebBoard. 4. Check the Announcements Page for other possible assignments. 3 U4LP3 2 of 3 5/7/200 3:50 PM

3 - Introduction to Unit 4 - Lesson (cont.) Following is an outline of the content of Unit 4 Cardiorespiratory Response to Exercise. The pertinent sections of this outline are also listed at the beginning of each lesson. The purpose of the outline here is to show how the topics of the entire unit are organized. Outline of Content I. Lesson Overview A. Overview of Unit and Lesson B. Glossary of Selected Terms and Abbreviations C. The Fick Equation D. Summary Introduction of Cardiorespiratory Variables Related to VO2 II. Lesson 2 Respiration A. Overview B. Ventilation C. Response of Minute Volume of Ventilation to Exercise D. Gas Exchange E. Gas Transport. Oxygen 2. Carbon dioxide F. Respiration and Acid-Base Regulation G. Regulation of Ventilation 4 U4LP4 3 of 3 5/7/200 3:50 PM

4 - Introduction to Unit 4 - Lesson (cont.) III. Lesson 3 Cardiovascular Physiology A. Introduction B. Cardiac Physiology C. Vascular Physiology D. Summary of Cardiovascular Responses to Exercise. Introduction 2. Cardiovascular Responses to Acute Volume-Overload Exercise 3. Cardiovascular Adaptations to Volume-Overload Training 4. Cardiovascular Responses to Acute Pressure-Overload Exercise 5. Cardiovascular Adaptations to Pressure-Overload Training 5 U4LP5 4 of 3 5/7/200 3:50 PM

5 - Introduction to Unit 4 - Lesson Learning Objectives Specific learning objectives related to just Lesson are listed below. They are relatively few in number, because this is an introductory lesson. Specific learning objectives for the other lessons in this unit are listed at the beginning of each lesson. If you fulfill all of those objectives, you will understand the most important concepts presented in the unit. Therefore, you should use the objectives as a study guide, to check whether you understand the most important points. But, the objectives certainly do not exhaustively address everything one should know to thoroughly understand the course content. Therefore, I urge you to seek understanding beyond the listed objectives. In addition to the lists of specific objectives, at the end of each lesson I have listed additional activities that should help you in your reviews. Also, we will discuss various topics in the lessons in WebBoard conferences. You should feel free to post your questions for discussion on the WebBoard. After completion of Lesson, the student should be able to:. Define common terms used in cardiorespiratory exercise physiology. 2. Discuss the Fick Equation, including answers to the following questions: What is the basic Fick Equation related to VO2? What is the value of the Fick Equation in its various forms? What are variables that can be directly related to VO2 via the Fick Equation? 6 U4LP6 5 of 3 5/7/200 3:50 PM

6 - Cardiorespiratory Exercise Physiology The term cardiorespiratory is used to refer to everything related to blood flow and respiration. Literally, cardio refers to just the heart. But the cardio in cardiorespiratory refers to the entire circulatory system, including the heart and the vascular system (blood vessels), and anything else related to their function. As noted in the Introduction to the Unit, Lesson 2 of this unit will address the respiratory aspects of cardiorespiratory, and Lesson 3 will address the cardio-circulatory or cardiovascular aspects. I want to do three things in this first lesson in terms of concepts: I will present a list or glossary of basic terms you should know to help you to understand cardiorespiratory exercise physiology, and specifically the more expanded discussions in Lessons 2 and 3. As a part of the glossary, I will give common abbreviations. As mentioned elsewhere in this course, abbreviations are part of the essential vocabulary and jargon of any discipline. I will present an overview of cardiorespiratory physiology using the Fick Equation, in its various forms, as an outline. I will present a summary introduction of individual cardiorespiratory variables that are directly related to oxygen consumption (VO2). 7 U4LP7 - Glossary of Selected Terms and Abbreviations 6 of 3 5/7/200 3:50 PM

7 alveolar ventilation. The process of exchanging air between the atmosphere and the gas-exchange regions (respiratory zone) of the lungs. This can also be expressed as the amount of air exchanged per minute, the minute volume of alveolar ventilation (VA) in ml/min or L/min. arterial oxygen content (CaO2). The concentration of oxygen in the arterial blood. Usually expressed in milliliters of oxygen per deciliter (00 ml) of blood (ml O2/dL blood). arterial-venous oxygen difference (a-v O2 diff). The mathematical difference between the content (concentration) of oxygen in the arterial blood and the content of oxygen in the venous blood. When considering the entire body, the term mixed venous is used. Mixed venous blood is sampled from the very end of the systemic circulation, before the blood returns to the lungs to add oxygen. It represents the average of the venous blood that has drained all the tissues of the body. Usually expressed in milliliters of oxygen per deciliter (00 ml) of blood (ml O2/dL blood). cardiac cycle. One complete series of events in the heart that includes systole and diastole. cardiac output (C.O.). The volume of blood pumped by the heart per minute. Usually expressed in liters of blood per minute (L/min). dead space (DS). The segments of the pulmonary system in which air does not undergo gas exchange with the blood. Often expressed as a volume (ml). diastole. The portion or phase of a cardiac cycle during which the heart muscle is not contracting. diastolic blood pressure (DBP). The pressure in a given part of the arterial circulation when it is at its lowest during diastole. Usually expressed in millimeters of mercury (mm Hg). end-diastolic volume (EDV). The volume of blood in a specific chamber of the heart at the end of diastole. Expressed in liters (L) or milliliters (ml). end-systolic volume (ESV). The volume of blood in a specific chamber of the heart at the end of systole. Expressed in liters (L) or milliliters (ml). heart rate (HR). The number of times the heart beats per minute, or the number of cardiac cycles per minute. Expressed in beats per minute (bpm). hemoglobin (Hb). The iron-containing protein in red blood cells that has a primary function of reversibly binding oxygen. Concentration in blood is expressed as grams of Hb per deciliter (00 ml) of blood -- g/dl. 7 of 3 5/7/200 3:50 PM

8 8 U4LP8 - Glossary of Selected Terms and Abbreviations cont. mean (arterial) blood pressure (MAP). The average arterial blood pressure over the course of one complete cardiac cycle. Usually expressed in millimeters of mercury (mm Hg). minute volume of ventilation. The total volume of air either breathed out of (VE) or breathed into (VI) the lungs per minute. Expressed in L/min or ml/min. mixed venous blood (often abbreviated as a v with a bar over it, similar to bar-x indicating mean or average). Blood that represents a weighted average of the venous blood that has drained all tissues in the body, prior to entering the pulmonary capillaries for gas exchange. partial pressure (P). The pressure of a single gas in a mixture of gases or in solution (e.g., in the blood). Usually expressed in mm Hg. pulmonary ventilation. The process of exchanging air between the lungs and the atmosphere outside the body. stroke volume (SV). The volume of blood ejected from the heart in a single beat. Expressed in liters (L) or milliliters (ml) per beat. systole. The portion or phase of a cardiac cycle during which the heart muscle is contracting. systolic blood pressure (SBP). The pressure in a given part of the arterial circulation when it is at its highest during systole. Usually expressed in millimeters of mercury (mm Hg). tidal volume (TV or VT). The volume of air breathed in or out in a single breath. total peripheral resistance (TPR). The resistance to blood flow provided by the entire vascular system. venous oxygen content (CvO2). The concentration of oxygen in the venous blood. Usually expressed in milliliters of oxygen per deciliter (00 ml) of blood (ml O2/dL blood). 8 of 3 5/7/200 3:50 PM

9 9 U4LP9 - The Fick Equation The Fick Equation describes the mathematical relationship among different cardiorespiratory variables. We will not do much with this equation in terms of quantitative manipulations, although more advanced students will gain deeper understanding of exercise physiology by doing so. One reason I am addressing the Fick Equation here is that no course could claim to be an overview course in exercise physiology without at least mentioning the Fick Equation. The more important reason is that this equation makes an excellent outline for studying cardiorespiratory physiology in general, and the cardiorespiratory responses to exercise in particular. On the next page is a list of equations starting with the basic Fick Equation and followed by expansions of the Equation in different ways to include different variables. Here, I am going to just list the equations. I will not give mathematical examples or present explanations. The next two lessons will address specific aspects of these equations and the relationships they describe. We will also address these further in conference discussions. You should refer back to the list of terms presented earlier in this lesson as you need reminders of definitions or abbreviations. I will express the equations with reference to rate of oxygen consumption (VO2). A similar list of equations could be presented with reference to rate of carbon dioxide production (VCO2). The Fick Equation is often used by physiologists to study just one body segment. Let s assume that we are dealing with the whole body. 0 U4LP0 9 of 3 5/7/200 3:50 PM

10 - The Fick Equation (cont.) The basic Fick Equation: VO2 = C.O. x (a-v O2 diff) Variations of the Fick Equation involving different expressions of cardiac output VO2 = HR x SV x (a-v O2 diff ) VO2 = HR x (EDV - ESV) x (a-v O2 diff ) VO2 = (MAP / TPR) x (a-v O2 diff ) During exercise, MAP is approximately the average of the systolic and diastolic blood pressures. Therefore, during exercise: VO2 = (((SBP + DBP) / 2) / TPR) x (a-v O2 diff ) Variations of the Fick Equation involving different expressions of a-v O2 difference VO2 = C.O. x (CaO2 CvO2) Ignoring the very small amount of oxygen that is dissolved in blood when breathing normal atmospheric air: VO2 = C.O. x.34 x [Hb] x (SaO2 SvO2) [Hb] = concentration of hemoglobin in the blood; S = the % saturation of hemoglobin with O2, expressed as a fraction. U4LP 0 of 3 5/7/200 3:50 PM

11 - The Fick Equation (cont.) Wasn t that exciting! I know the mathematicians among us are drooling over the thought of plugging numbers into those equations and calculating results. What about the rest of us? I do encourage you to look at each equation to try to understand the relationship among the variables that is expressed in the equation. And we will examine some of these in more details in Lessons 2 and 3. But the primary objective of listing these equations is to impress on you the different variables that are related in some way to VO2. We have studied VO2 extensively in this course, and we know how important VO2 is in energy metabolism. It is a critical physiological variable, as well as a very useful variable to measure in the laboratory to give important information about energy metabolism. Every equation above shows that if VO2 changes (as it must during exercise), at least one of the variables on the other side of the equation must also change. For example, the basic Fick Equation states: VO2 = C.O. x (a-v O2 diff). Since we know that VO2 increases in response to acute exercise, this equation tells us that cardiac output and/or arterial-mixed venous oxygen difference changes also. In fact, during dynamic exercise, compared with the resting state, as VO2 increases there normally are increases in both cardiac output and a-v O2 difference. In other words, there are cardiorespiratory adaptations to acute exercise that have to take place to support the increased oxygen consumption of skeletal muscle fibers in aerobic metabolism. Similarly, we know that VO2max typically increases in response to endurance training. The Fick Equation tells us that for VO2max to change, there has to be some change in the cardiac output and/or a-v O2 difference values associated with VO2max. In other words, there must be cardiorespiratory adaptations to the endurance training 2 U4LP2 of 3 5/7/200 3:50 PM

12 - Summary Introduction of Cardiorespiratory Variables Related to VO2 Before going on to more detailed discussions of respiratory and cardiovascular exercise physiology in the next lessons, I want to present one more list. Following is a list of every variable in the equations listed previously. I am listing these partly to impress upon you the many cardiorespiratory factors that can, and often do, change in response to exercise and other stresses to support the needs of the body s tissues. Also, I am listing these variables to guide your studying of cardiorespiratory exercise physiology. Thorough understanding of this topic requires understanding of the response of each of these variables to acute and chronic exercise. Variables related to VO2: C.O. cardiac output a-v O2 diff arterial-venous oxygen difference HR heart rate SV stroke volume EDV end-diastolic volume ESV end-systolic volume MAP mean arterial pressure TPR total peripheral resistance SBP systolic blood pressure DBP diastolic blood pressure CaO2 content (concentration) of oxygen in arterial blood CvO2 content (concentration) of oxygen in venous blood [Hb] hemoglobin concentration in the blood SaO2 saturation of arterial blood (hemoglobin) with oxygen SvO2 saturation of venous blood (hemoglobin) with oxygen Unfortunately for the beginning student, this list is not exhaustive. It includes just variables that can be quantitatively and fairly directly linked to VO2. Many other variables relate to the cardiorespiratory response to exercise. We will study some of those in the rest of this unit, as well as the variables in the list above. Attention to other variables will have to await more advanced study by those who choose it. 2 of 3 5/7/200 3:50 PM

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