Fisiologia Cardiovascular Integrada - Ingles

Integrated cardiovascular physiology: a laboratoryexercise. R D Patil, S V Karve and S E DiCarlo Advan in Physiol Edu 265:S20, 1993. You might find this additional info useful... Updated information and services including high resolution figures, can be found at: http://advan.physiology.org/content/265/6/S20.citation Additional material and information about Advances in Physiology Education can be found at: http://www.the-aps.org/publications/advan This information is current as of April 16, 2012. Downloaded from advan.physiology.org on April 16, 2012 Advances in Physiology Education is dedicated to the improvement of teaching and learning physiology, both in specialized courses and in the broader context of general biology education. It is published four times a year in March, June, September and December by the American Physiological Society, 9650 Rockville Pike, Bethesda MD 20814-3991. Copyright © 1993 by the American Physiological Society. ISSN: 1043-4046, ESSN: 1522-1229. Visit our website at http://www.the-aps.org/. Northeastern Ohio Universities. and the students are challenged to analyze and assimilate information from figures. . and apply basic concepts. The answers to the questions are provided in the APPENDIX. The special populations were chosen because of their unique limitations and adaptations.physiology. make calculations. teaching tool.org on April 16. Sangeeta V. Patil. In addition. which directly influence cardiovascular function. DiCarlo Department of Physiology. o 1993 Studying the cardiovascular responses to exercise ’ provides a unique opportunity to integrate and apply the principles of cardiovascular physiology. and students do not have the opportunity to apply the concepts. the system is most often presented as a physical model independent of neural influences. and plot graphs. Therefore. individuals with quadriplegia and heart transplantation were compared and contrasted with sedentary and endurance-trained individuals. The laboratory does not require any equipment or software. J. Therefore. THE AMERICAN IN PHYSIOLOGY s20 PHYSIOLOGICAL EDUCATION . answer questions. Rootstown. PWSIOL. Basic anatomic and physiological data about the special populations are provided. Each individual has unique autonomic and physiological control mechanisms regulating cardiovascular function. College of Medicine. which directly influence cardiovascular function.COPYRIGHT I -ADVANCES 1993. and an individual with heart transplantation. each cardiovascular component is presented independently. Karve. Ohio 442 72 xamining the hemodynamic responses to exercise provides a unique opportunity to analyze and integrate cardiovascular physiology because more is learned about how a system operates when it is forced to perform than when it is idle. education Teaching cardiovascular physiology is a challenge to even the most gifted educator. We designed a laboratory exercise that examines the cardiovascular responses to exercise in a sedentary individual. and very little time is scheduled to discuss the interaction between components.4046 VOLUME / 93 . The special populations were chosen because of their unique limitations and adaptations. This exercise should be attempted after the cardiovascular section of the physiology course so that the students can integrate and apply the information presented during the course. This laboratory exercise should be attempted in a group to foster discussions and interactions. More is learned about how a system operates when it is forced to perform than when it is idle (3). 2012 AM. E 265 (ADV PHYiSIOL. an athlete. an individual with quadriplegia. This method of teaching provides limited experience in evaluating and understanding the integrated cardiovascular system. 1043 . More emphasis should be placed on the application of basic science principles. integrate. An enormous amount of information must be disseminated in a relatively short period of time. and Stephen E. to help students analyze. when educators discuss interactions. and problem-solving skills (1) .$2:00 IO : NUMBER .DECEMBER SOCIETY 1993 Downloaded from advan. Traditionally. IO): S20-S31. interpretation of pictorial or tabular material. EDUC.I N N 0 V A INTEGRATED T I 0 N S A N CARDIOVASCULAR A LABORATORY D I D E A S PHYSIOLOGY: EXERCISE Rahul D. we developed a learning tool that evaluates cardiovascular responses during exercise in special populations. and oxygen consumption during exercise with no change in the maximum heart rate. the students are presented with basic anatomic and physiological information about each population. w-t 70 kg) with specific limitations or adaptations. The following narrative will describe the unique characteristics of each individual.physiology. VOLUME IO : NUMBER I . and the students are challenged to analyze the cardiovascular changes that occur during exercise. BACKGROUND INFORMATION The cardiovascular responses during dynamic exercise are examined in four males (age 30 yr. 2012 This game should be attempted after completing the cardiovascular section of the physiology course. and the efficiency of venous return. keeping in mind the limitations and adaptations present in each individual. With complete motor function. make calculations. unlike the individual with quadriplegia. there is a lower heart rate and higher stroke volume at rest. venous return. Decreases in cardiac parasympathetic efferent activity and/or increases in cardiac sympathetic efferent activity increase heart rate. while maintaining homeostasis. The answers to all the questions are provided in the APPENDIX. and plot data related to that figure. A . the students are prepared to integrate the information assimilated during the section and are ready to apply the information to special populations.. there IN PHYSIOLOGY s21 N EDUCATION . The purpose of this game was not to provide new information but to help the student apply the information already assimilated and provide insights concerning cardiovascular regulation. the available muscle mass for exercise. has full innervation to the heart and circulation and therefore has cardiovascular responses different from the individuals with quadriplegia and heart transplantation. a figure is presented that shows the response of a specific cardiovascular variable during exercise (e. However.. resulting in the loss of sympathetic and motor control below the level of the lesion. The students answer questions.I N N 0 V A T I 0 N S To begin this quest of understanding the integrated cardiovascular system. Individual With Quadriplegia The individual with quadriplegia has a transverse spinal lesion at the C. However. Trained Endurance Athlete The athlete has significant autonomic adaptations associated with exercise training. Exercise training is associated with a higher stroke volume. cardiac output. of course. and cardiovascular function. The individuals are different in the extent of innervation to their heart and blood vessels. this individual has complete motor function. which directly influences the maximum work load.C8 spinal level. causing an initial rapid increase in heart rate due to withdrawal of parasympathetic efferent activity. These autonomic adaptations make him uniquely suited to perform exercise. parasympathetic innervation to the heart is maintained. Sedentary Individual The sedentary individual has no significant limitations. this individual has full use of the muscle venous pump and can therefore take advantage of the Frank-Starling mechanism and exercise at a much higher work load. Heart rate is under the influence of the autonomic nervous system.org on April 16. there is a centrally mediated simultaneous activation of the cardiovascular and motor centers (central command). The answers do not involve difficult calculations or new information. THE GAME Heart Rate Figure 1 presents the relationship between heart rate and increasing work load. This individual. heart rate).ADVANCES Individual D I D E A S With Heart Transplantation The individual with a heart transplantation can be directly contrasted with the individual with quadriplegia.g. The donor heart is void of all sympathetic innervation and all significant parasympathetic innervation.100 beats/min. Once heart rate reaches . work load is expressed as the oxygen consumption required to perform the work. In addition. This individual is limited to arm exercise (arm cycle ergometry).DECEMBER 1993 Downloaded from advan. Subsequently. At this time. At the onset of exercise. cardiac sympathetic efferent activity. 2012 FIG.DECEMBER 1993 Downloaded from advan. however. cardiac sympathetic efferent activity also increases. What accounts for the similarity in stroke volume? 5) Compare the resting heart rate. How does the absence of cardiac parasympathetic innervation affect the heart rate response to exercise? 2) Compare the maximum heart rate response to exercise in the individuals with quadriplegia and heart transplantation. How would the absence of cardiac innervation affect the heart rate response to exercise? 7) Compare the stroke volume response in the sedentary individual with the response in the individual with heart transplantation. 0. athlete. and afterload. and maximum heart rate in VOLUME IO : NUMBER 1 . stroke volume can also increase slightly because of the effect of circulating catecholamines activating P. What accounts for the similarity in maximum heart rate? 3) What factors contribute to the increase in heart rate in the individuals with quadriplegia and heart transplantation? Questions 6) Compare the stroke volume responses in the individuals with quadriplegia and heart transplantation. reaching a maximum at 40-45% of the oxygen uptake at maximum exercise @o 2max). circulating catecholamines. the sedentary and athletic individuals. H. 125- 5 80- y 100 2 60- 0 K 75 40200: - 0 9 1 - 1 - 2 OXYGEN 8 3 - ’ 4 CONSUMPTION - ‘7 ’ 5 6 -1 7 (Umin) is a further increase in heart rate due to activation cardiac sympathetic efferent activity. How are they different? What accounts for this difference? of Stroke Individuals with heart transplantation and quadriplegia do not have sympathetic innervation to the heart. How are they different and what accounts for this difference? 4) Compare the heart rate response to exercise in the individual with heart transplantation with the sedentary individual. sedentary. Consequently. 0.-adrenergic receptors on the myocardium. Stroke volume increases during exercise.physiology. Figure 2 presents the stroke volume response to increasing work loads in the four individuals. cardiac transplant. During exercise. slope of the increase in heart rate.I N N 0 V A T I 0 N S A N D I D E A S 2501 180z160$140- 175- E 120- ! 3 150- ' d loo- 7: . Questions I> Compare the heart rate response to exercise in the individuals with quadriplegia and heart transplantation. enddiastolic volume increases and causes a stronger systolic contraction of the ventricle. venous return increases because of an increase in the activity of the muscle venous pump. . 1 Relationship between heart rate and increasing work load. quadriplegia. in accordance with the Frank-Starling law. the individual with quadriplegia has cardiac parasympathetic innervation.org on April 16. During exercise. Finally. Stroke volume is a function of venous return.ADVANCES Volume IN PHYSIOLOGY s22 EDUCATION . 0. Work load is expressed as oxygen consumption required to perform the work. Thus oxygen consumed by the body is determined by measuring cardiac output and the oxygen content of the arterial and mixed venous blood. g 35E .DECEMBER 1993 Downloaded from advan.15 g Hb/lOO ml. 4 output response to exercise in the 4 individuals. = CO 9) With the use of Figs. 1870) can be i70. calculate the cardiac output response during exercise in the four individuals. of 100 mmHg is -98%.physiology. IN PHYSIOLOGY S23 EDUCATION . The oxygen saturation of arterial blood with a PO. How are they different and what accounts for this difference? The Fick principle written (Adolph Fick.75%. 3 cardiac 5 6 7 12) Compare the cardiac output responses in the sedentary and athletic individuals. whereas that of mixed venous blood with a PO.34-1. How are they different and what accounts for this difference? 2 OXYGEN relation between (quesHort 9). The increase in cardiac output is due to an increase in heart rate and stroke volume. n . CO is cardiac output. Increases in stroke volume contribute . 3 CONS 4 UMPTION 5 FIG. calculate the arteriovenous oxygen difference response to exercise in the four individuals. Plot these results in Fig. Cardiac Output Figure 4 presents the cardiac output response to exercise in the four individuals. of 40 mmHg is .15.36 ml of oxygen. How are they different and what accounts for this difference? (Umin) output and oxygen con- 8) Compare the stroke volume responses in the sedentary and athletic individuals. Accordingly. 4 FIG. (Umin) 1 . and (a-v)02 is the arteriovenous oxygen difference.ADVANCES 0. 5.20. q .6 ml oxygen/l00 ml blood.8 ml oxygen/l00 ml blood. Question 2 OXYGEN Cardiac athlete. E lo2 * o 5- X (a-v)02 where to2 is oxygen consumption. Plot these results in Fig. to increases in cardiac output up to 40-45% of vo 2max* Further increases in cardiac output are due to increases in heart rate. provided the flow rate and the oxygen content of blood samples are known.org on April 16. sedentary. cardiac transplant. 2 30% 25k 3 0 Calculating Oxygen Consumption: The Fick Principle 20* 5: 15.I N N 0 V A T I 0 N S A N D I D E A S Questions 401 10) Compare the cardiac output responses to exercise in the individuals with quadriplegia and heart transplantation. 3. One gram of hemoglobin (Hb) can combine with 1. Because normal blood has . and the oxygen capacity of venous blood is . How are they different and what accounts for this difference? 11) Compare the cardiac output responses in the sedentary individual and the individual with heart transplantation. 2012 Plot the sumption 3 CONSUMPTION . quadriplegia. the oxygen capacity of arterial blood is . l . oxygen consumed by the body is the product of cardiac output and the arteriovenous oxygen concentration difference. 1 and 2. This equation is used to calculate cardiac output or blood flow to any organ. 4 and the Fick principle. It can also be used to calculate the oxygen consumption of the entire body or any organ. VOLUME IO : NUMBER 13) Using Fig. 8 ml/100 ml)-venous (15. =o! - ’ - 1 0 ’ - 2 OXYGEN Plot the relation ence and oxygen ’ - ’ 3 = 4 CONSUMPTION - 1’ ’ 6 7 ’ 0 I - 1 (a-v) 13). - ’ - 3 ’ 4 CONSUMPTION - 1. 0. How are the increased and l . The maximum arteriovenous oxygen difference is comparable in the four individuals (. 6 and 7). cardiac transplant.physiology. this reserve is quite small. athlete. sedentary. 5 between arteriovenous consumption (question Arteriovenous ’ 5 D . differ- E ’ 2 OXYGEN (Umin) FIG. The oxygen content of venous blood draining the heart is low relative to that of other organs. oxygen extraction in the circulation to the active muscles is nearly complete at maximum exercise. Although the myocardial oxygen extraction increases during severe exercise. exercise. giving a wide arteriovenous oxygen difference. 6 between arteriovenous oxygen difference work loads in the 4 individuals.ADVANCES 16) Compare arteriovenous oxygen difference response to exercise in the coronary and systemic circulations (Figs. oxygen consumption increases. Because oxygen requirements of the exercising muscles increase significantly during S - 4 ’ 5 - ’ 6 - ’ 7 (Umin) oxygen difference in work loads in the 4 q . 2012 Oxygen Difference A CONSUMPTION FIG. Oxygen consumption of the whole heart can be determined using the Fick equation. quadriplegia. q I. n . ko! - 0 ’ 1 - ’ 2 OXYGEN Relationship increasing sedentary. quadriplegia.N N 0 V A T I 0 N S A N 0:. athlete. oxygen consumption is -250 ml oxygen/ min. The increased requirements for oxygen are met by increasing cardiac output (delivering more oxygen) and extracting more oxygen from the arterial blood (increasing arteriovenous oxygen difference). Oxygen extraction increases more slowly than cardiac output. IN PHYSIOLOGY S24 EDUCATION . Questions 14) What accounts for the difference in arteriovenous oxygen difference response to exercise in the sedentary individual and the athlete? 15) What accounts for the difference in maximum oxygen consumption of the sedentary and athletic individuals? Myocardial Oxygen Consumption Figure 7 presents the relationship between the arteriovenous oxygen difference in the coronary circulation and increasing work loads.5 ml oxygen/100 ml blood. oxygen D “1. “1 5 6 FIG.0 ml/100 ml) oxygen difference is therefore . 3 Figure 6 presents the relationship between arteriovenous oxygen difference and increasing work loads. The arterial (20. even under resting conditions. At rest. As the work intensity increases.16-18 ml/100 ml blood).org on April 16. VOLUME IO : NUMBER 7 Question (Umin) 1 . 0. cardiac transplant. l . 0.DECEMBER 1993 Downloaded from advan. 7 Relationship between arteriovenous coronary circulation and increasing individuals. sedentary. thereby increasing the diastolic pressure.physiology. and diastolic blood pressure. I 5 - I 6 ’ I 7 (Umin) to exercise q I. 0.I g 250 E vL 200 N N 0 V A T I 0 N A S N D I D E A S 1I Iii .DECEMBER 1993 Downloaded from advan. Diastolic blood pressure (pressure during diastole. stroke volume is the major determinant of systolic blood pressure. 0. athlete. W. 2012 8 Relationship between systolic blood pressure and increasing work loads in the 4 individuals. Normally diastolic blood pressure remains the same or changes only moderately during exercise because although heart rate increases. An increase in the peripheral vascular resistance also causesa decrease in outflow of blood. 0 5o = 0 . l I 3 - I 4 - CONSUMPTION FIG. cardiac transplant. The arterial blood volume is the net result of the rate of blood flow from the heart to the arteries and the rate of outflow from the arteries through the resistance vessels.ADVANCES IN PHYSIOLOGY S25 EDUCATION . 9 response . depends on the magnitude of the increase in heart rate and decrease in peripheral vascular resistance. n . 4 myocardial oxygen requirements during exercise fulfilled? 19) Compare the systolic blood pressure response to exercise in the athlete and the sedentary individual. Differences in rate of ejection and diastolic blood pressure also account for the difference in systolic blood pressure response to exercise in the four individuals. Diastolic blood pressure in- Questions 17) Compare the systolic blood pressure response to exercise in the individuals with quadriplegia and heart transplantation. diastolic blood pressure is a function of heart rate and peripheral vascular resistance. therefore. Therefore. How are they different. $0 G O ~1~l-1’1’1~1~1 1 2 OXYGEN 3 4 CONSUMPTION 5 6 I 1 7 (Umin) I 2 - OXYGEN FIG. and what accounts for this difference? 18) Why is the systolic blood pressure response in the individual with heart transplantation lower than that in the sedentary individual? VOLUME IO : NUMBER 1 . when the heart is active) is the pressure generated by stroke volume during ventricular systole. 2 E 150E 8 0 d loo. The diastolic blood pressure response to exercise. How are they different and why? Systolic Blood Pressure Diastolic Blood Pressure Figure 8 presents the relationship between systolic blood pressure and increasing work loads in the four individuals. athlete. peripheral vascular resistance decreases. quadriplegia. cardiac in the transplant.org on April 16. Diastolic blood pressure individuals. q. vessel wall compliance. Systolic blood pressure (pressure during systole. when the heart is at rest) is the pressure exerted by the volume of blood that remains in the arteries after the peripheral runoff of blood from the arteries through the resistance vessels. Increases in heart rate increase the rate of inflow of blood and reduce the time during which outflow occurs through the resistance vessels. If one assumesthat the compliance of the blood vessels is similar in the four individuals. 0. the peak rate of ejection. - . quadriplegia. sedentary. Systolic blood pressure is a function of left ventricular stroke volume. Figure 9 presents the diastolic blood pressure response to exercise in the four individuals. which results in an increase in diastolic pressure. m or 1 kp m of work. whereas it decreases in the sedentary individuals and athletes. This is often described as the perfusion pressure or the pressure necessary to maintain adequate blood flow to the tissues. It is possible to utilize either units of work.I N N 0 V A T I 0 N S A sI creases slightly with increasing work loads in the individuals with heart transplantation and quadriplegia. calculate the mean arterial pressure response during exercise in the four individuals. and pulse pressure (PP) equals systolic pressure minus diastolic pressure.physiology. Work or the energy required to perform work is quantified in a variety of units depending on the VOLUME IO : NUMBER I . such as kilopond -meters or joules.m of work is equal to 1. l Question work arterial EDUCATION . or making nutritional adjustments in obese individuals. such as oxygen consumption (ml/min). or units of energy expenditure. Mean arterial pressure is the average pressure throughout the cardiac cycle. Power is work performed per unit time. when modifying the activity profile of patients with myocardial infarction. For example. and activity levels. the mean pressure is slightly less than the value halfway between systolic and diastolic pressures. Because systole is shorter than diastole. 22) Using Figs. the physician must convert the activity or work performed by the patients (activities of daily living) to units of energy expenditure. the rate of peripheral outflow. For example. 10. lifting 1 kg vertically through 1 m results in 1 kg. vascular compliance. Plot these results in Fig. the oxygen l l units pressure situation. The oxygen cost of 1 kp. 21) What does the rise in diastolic blood pressure with exercise signify? OXYGEN CONSUMPTION FIG.org on April 16. 8 and 9.DECEMBER 1993 Downloaded from advan. To account for the added frictional work on a cycle ergometer. and the rate of ventricular ejection vs. 2012 Pulse pressure is the difference between the systolic and diastolic blood pressures. so it is estimated in units of kilopond *meter per minute. DP is diastolic pressure. N D I D E A S 250 E Questions 20) Explain the response of diastolic blood pressure to exercise in the athlete and the sedentary individual.ADVANCES IN PHYSIOLOGY s26 and oxygen Work on a cycle ergometer is conventionally estimated in units of kilopond meter (kp m). or metabolic equivalent terms (METS). Compare the mean arterial pressure response to exercise in the sedentary individual and the athlete. dietary restrictions. adjusting the insulin requirements of individuals with diabetes.8 m/s* (gravitational acceleration). Work is force applied over a specific distance. This process allows the physician to prescribe appropriate medications. Clinicians are encouraged to understand the relationships between work and energy expenditure because they will be required to utilize these facts in a variety of patient populations. For all practical purposes it is calculated by the formula MAP=DP+1/3PP where MAP is mean arterial pressure. kilocalories. because there is a linear relationship between these units. The major factors affecting pulse pressure are stroke volume.8 ml of oxygen. Pulse pressure is a function of the volume of blood ejected by the left ventricle during systole (rapid ejection phase) minus the volume of blood that runs off to the periphery during diastole. A kilopond is defined as the amount of force required to accelerate a mass of 1 kg by 9. Mean Arterial Pressure Response Plot the relation between mean consumption (question 22). (L/min) 10 . Work quantitated on a cycle ergometer (or other device) can be converted to energy consumption by knowing some basic facts. especially when corrected for body weight.. 2 METS. I ’ X - 8 1 (L/min) ” .ADVANCES Questions 23) Examine the relation between Vo2. 0 ‘l’l’l-8. .org on April 16. submaximal. 3.82) energy consumed (kcal/min) = 5 kcal/l O2 x Vo. The work performed (estimated in terms of kcal/ min) also has a linear relationship with oxygen consumption at steady-state. 2012 MET = Vo. the oxygen cost of work against the applied load is 2 ml of 02/(kp mm). 1 81.1-r-l 0 5 Plot the 2342). A N D I D E A S l 10 i/-o. One metabolic equivalent term is equal to the oxygen consumed by a human being at rest. and it increases with the degree of physical conditioning. walking.m/min FIG. kcal/min. termed Vozmax. In exercise physiology. Thus units of oxygen consumption can be directly converted to METS by understanding the following relationship I .DECEMBER 1993 Downloaded from advan. 12 kcal/min 25 and 30 METS 35 (questfon exercise (assumingR = 0. 12 and 13. 12) b) kp m/min and Vo.2 ml OJ(kp m).correlates well with the degree of physical conditioning and has been accepted as an index of total body fitness. The Vozmaxis a reproducible value. kp l m/ 1 1 1 10 1 5 1 1. plot the relationship between a) METS and kcal/min (Fig. 3ooo kp.5 mlkg-lernin-l) where Vo* is in milliliters per minute and weight is in kilograms./(weight * 4 0 -I.e. 30 25 11 consumption (Vo2). aerobic VOLUME 1 IO : NUMBER I . 1000 . The capacity to consume oxygen is related not only to the effectiveness of the lungs but also to the ability of the heart and circulatory system to transport the oxygen and to the body tissue’s ability to metabolize it.m) x kp-m/min 5 + 250 ml/min 0 Go2 Thus there is a linear relationship between oxygen consumption and work load (2). Thus. i. This serves to guide the patients regarding the work loads that they perform. (kp -m) /min. between oxygen and METS. Whole body oxygen consumption increases in a linear fashion with increasing work. .. for cycle ergometry. The total oxygen consumption of an individual working on a cycle ergometer is thus obtained by adding the oxygen cost of work to resting oxygen consumption by the body (-250 ml/min). (l/min) 3. METS are frequently used to estimate work in clinical cardiology. 1. Various common work loads are quantitated in terms of multiples of oxygen consumption or multiples of METS (dressing and undressing.I N N 0 V A T I 0 N S cost of 1 kp-m of work is augmented by 0. 12 ’ 15 - ’ 20 * ’ 24 28 METS .. (7”’ 1. 11. The oxygen uptake at maximum exercise. relation 10 15 between 20 Kcal/min FIG. 0 7. .5 ml O2-kg-l -min. 1500 1. .. (ml/min) = 2 ml/(kp. 3 METS). . Relationship min.. Using Figs. kcal/min. and METS presented in Fig.physiology. 2500 2000 ‘. I. Vozmaxhas been used as a standard of comparison within and across subjects to normalize the effects of various absolute work loads. 13) l IN PHYSIOLOGY S27 EDUCATION .. (Fig. 3) Factors that contribute to the increase in heart rate in the individual with quadriplegia are withdrawal of the parasympathetic tone and the effect of circulating catecholamines. 15001000 5000 0 ' 1 = ' 2 OXYGEN Plot tion D 3500- . According to the clinical faculty. and therefore the athlete has a resting bradycardia. The students also enjoyed reading graphs and using rulers and pencils to plot data. The rise in heart rate is due to the effect of circulating catecholamines. - " 3 1" 4 CONSUMPTION FIG. From these experiences we know that the laboratory requires . heart rate does not rise further because of the absence of cardiac sympathetic efferent activity. the rise in heart rate occurs because of the effect of circulating catecholamines.3 h to complete. We acknowledge this concern.ADVANCES 2) The maximum heart rate responses in the individual with quadriplegia and heart transplantation are similar because the maximum increase in heart rate in both individuals is due to the effect of circulating catecholamines.I N N 0 V A T I 0 N S A I D E A S APPENDIX: 3000- Heart 2500- 1) The individual with heart transplantation does not have a rapid rise in heart rate at the onset of exercise because the heart has no significant autonomic innervation. The individual with quadriplegia has an initial rapid rise in heart rate due to the withdrawal of cardiac parasympathetic efferent activity.org on April 16. we feel that the faculty could edit this learning tool to suit their individual curriculum. 5) Autonomic adaptations associated with chronic endurance training result in an enhanced cardiac parasympathetic efferent activity. At this point it is important to note that circulating catecholamines (norepinephrine and epinephrine) increase heart rate by activating PIadrenergic receptors on the sinoatrial node. In addition. The students were excited about the opportunity to apply information assimilated over the entire cardiovascular section of the physiology course to specific populations. 4) The sedentary individual has an initial rapid increase in heart rate due to withdrawal of cardiac parasympathetic efferent activity and a further increase to an age-dependent maximum due to an increase in cardiac sympathetic efferent activity.physiology. 13 kp *m/mix-~ 5 " 6 1 7 (Umin) and oxygen QUESTIONS Rate The general consensus about the weakness of this laboratory exercise was that the time to solve this exercise was too long (.I E 20005 2 N the relation between (question 236). The subjects worked in groups of four. The physiology faculty appreciated the fact that it did not require any equipment or computers (in an era of educational budget cuts).3 h). and they appreciated the goals of having students analyze graphical data. The faculty were also impressed with the level of discussion that the exercise stimulated. The practical application of basic science principles was greatly appreciated. however. 2012 This laboratory exercise was attempted by faculty and students at our institution. whereas only the circulating catecholamines contribute to the increase in heart rate in the individual with heart transplantation. the strength of this learning tool was that the students applied basic science information to clinical situations. 10 : NUMBER TO GAME consump- DISCUSSION VOLUME ANSWERS . however. Note that the heart rate response at similar work loads is lower in the athlete compared with the sedentary individual.DECEMBER 1993 Downloaded from advan. There is no rapid rise in heart rate at the onset of exercise in the individual with heart transplantation because of absence of cardiac parasympathetic innervation. we presented this game at the Experimental Biology ‘93 meeting in New Orleans. 1 . IN PHYSIOLOGY S28 EDUCATION . the individual with quadriplegia has a reduced ability to increase total body oxygen consumption. the arteriovenous oxygen difference is lower in the athlete compared with the sedentary individual because the athlete has much higher cardiac output.DECEMBER 1993 Downloaded from advan.physiology. 2012 7) Stroke volume response to exercise is determined by end-diastolic volume. Myocardial Oxygen Consumption 16) Under resting conditions. In contrast. above this work load. therefore venous return is enhanced. however. cardiac sympathetic efferent activity. the maximum stroke volume achieved in the individual with heart transplantation is lower because of the absence of cardiac sympathetic efferent activity. both individuals achieve a similar agedependent maximum heart rate. the arteriovenous oxygen difference of the sedentary and athletic individuals is similar. and therefore cardiac outputs are similar. II) The cardiac output responses to exercise are initially comparable in the sedentary individual and the individual with heart transplantation. VOLUME A S . that because of large stroke volumes in the athlete. In contrast. l). which allows for a greater cardiac filling during diastole (greater enddiastolic volumes). This illustrates the importance of the Frank-Starling mechanism. the individual with heart transplantation has a normal muscle venous pump and muscle mass.org on April 16. he can achieve a much higher cardiac output (nearly double) compared with the sedentary individual. because of the reduced muscle mass. 2) at the same work load. he has a much higher stroke volume (Fig. Actually cardiac output is the factor limiting the maximum exercising capacity. 15) Even though the athlete and the sedentary individual have the same maximum arteriovenous oxygen difference. at work loads above 45% of qozmax. and therefore the stroke volume response to exercise is initially similar. heart rate.ADVANCES D I D E A S thetic efferent activity). Cardiac Output 10) The individual with quadriplegia has a very low cardiac output because stroke volume does not increase with exercise (no muscle venous pump). The lower cardiac output response in the individual with quadriplegia is therefore due to a severely limited stroke volume. Even though the athlete has a lower resting heart rate (Fig. therefore the stroke volume response in the athlete is much greater compared with that of the sedentary individual. circulating catecholamines. the cardiac output response is lower in the individual with heart transplantation because of the poor heart rate response to exercise. and total body oxygen consumption significantly increased. The muscle venous pump is functioning normally in both individuals. the individual with heart transplantation is able to increase stroke volume because of a functioning muscle venous pump. Note. and therefore venous return does not increase with exercise. Note that both individuals have a limited heart rate response to exercise (absence of cardiac sympa- IO : NUMBER 1 . However. In addition. 8) The athlete has a much higher stroke volume at similar work loads. In fact the individual with heart transplantation has a stroke volume comparable to that of the sedentary individual. The athlete has a larger ventricular volume and slower heart rate.I N N 0 V A T I 0 N however. Arteriovenous Oxygen Difference 14) up to 75% OfiTOImaxof the sedentary individual. and muscle mass. Stroke Volume 6) The individual with quadriplegia has no motor control below the level of the lesion (no muscle venous pump). and afterload. however. the arteriovenous oxygen difference in the coronary circulation is 12-14 ml/l00 ml compared with 4-5 ml/100 ml in IN PHYSIOLOGY S29 N EDUCATION . however. Thus the athlete is able to meet the increased oxygen requirements of the body by increasing cardiac output without significantly altering arteriovenous oxygen difference homeostasis. 12) Cardiac output in the sedentary individual and the athlete are similar at lower work loads. the difference in the GoZmaxis due to the difference in the cardiac output between the two individuals. A .ADVANCES D I D E A S tance. which reflexly increase total peripheral resistance. the individual with quadriplegia has a reduced functioning muscle mass. Systolic Blood Pressure 18) The systolic blood pressure response to exercise is lower in the individual with heart transplantation compared with the sedentary individual because of a lower stroke volume response to exercise (absence of cardiac sympathetic efferent activity). In response to exercise the maximum arteriovenous oxygen difference in both circulations is similar (16-N ml/100 ml). kp. 5 kcal/min. impaired cardiac performance results in a reduced systolic blood pressure response to exercise. IN PHYSIOLOGY s30 N EDUCATION . therefore. 22) The mean arterial pressure response to exercise in the sedentary individual and the athlete is the same. One liter of oxygen consumed per minute is equivalent to 426. Therefore diastolic pressure decreases (metabolic vasodilatation). the mean arterial pressure response to exercise is nearly the same in the athlete and the sedentary individual. and 4.I N N 0 V A T I 0 N S the systemic circulation. However. but he also has a lower diastolic blood pressure response to exercise. Thus the heart works against a decreased afterload.m/min and kcal/min. 21) Normally diastolic blood pressure decreases in response to exercise. in the individuals with heart transplantation and quadriplegia. SUMlMARY This game was designed as a laboratory exercise to help students apply basic principles of cardiovascular physiology. to maintain perfusion pressure.08 METS. diastolic pressure will not decrease. Diastolic Blood Pressure 20) Diastolic blood pressure decreases in response to exercise (despite the increase in heart rate) because of a decrease in the total peripheral resistance. Total peripheral resistance can decrease more in the athlete because the athlete has an increased cardiac performance and much higher systolic pressure. 11 and the equations following it that there are linear relationships between the units used to quantify work: oxygen consumption. Therefore the increased myocardial oxygen demands during exercise are primarily met by increases in the coronary flow.m)/min. During exercise. resulting in a large increase in cardiac output and systolic blood pressure. 2012 17) The systolic blood pressure response in the individual with quadriplegia is much lower than that in the individual with heart transplantation because of the poor stroke volume response to exercise. perfusion pressure is monitored and maintained by the arterial baroreflex and muscle metaboreflex.85 (kp. If cardiac performance is not adequate enough to maintain perfusion pressure.physiology.and metaboreflex) during exercise and still maintains perfusion pressure. The high systolic pressure response allows diastolic pressure to decrease (metabolic vasodilation without activation of baro. The reduced systolic blood pressure response activates the arterial baroreflex and muscle metaboreflex. METS. That is. Total peripheral resistance will decrease because of metabolic vasodilatation. 19) The athlete has a much higher systolic blood pressure response to exercise than the sedentary individual because of a larger stroke volume and a more rapid rate of its ejection.org on April 16. Because cardiac performance is so high in the athlete. Therefore. and in severe casesit will increase because of an increase in total peripheral resistance. The athlete has a higher systolic blood pressure response to exercise. The reduced stroke volume response to exercise is due to the failure of cardiac performance to increase resulting from an absence of the muscle venous pump and reduced muscle mass. and this also contributes to his inability to decrease total peripheral resistance because there is a reduced metabolic vasodilatation. the diastolic pressure rises in response to increasing work loads because of impaired cardiac performance. In addition. these reflexes are not activated to increase total peripheral resis- VOLUME IO : NUMBER I . Work Units 23) It can be seen from Fig. This is a major advantage to the athlete. the arterial baroreflex and muscle metaboreflex reflexly increase total peripheral resistance. Thus the coronary circulation has a very small reserve for extracting oxygen.DECEMBER 1993 Downloaded from advan. which maintains perfusion pressure. assimilate information from graphs. OH 44272. We suggest that students work in groups of four or five to foster discussion and interactions.. Ludbrook. Dept. R. NIPS 7: 152-156. 5. New York: Oxford University Press. B. We sincerely appreciate the excellent the preparation of this manuscript. Rev..). Tenney.: S13-S15. 2. p. S. Suppl. 290-291. R. Saltin. and K. 1986. 6..1989.I N N 0 V A T I 0 N S A and understand the integrated cardiovascular system. The unanswered question. PhysioZogicaZ Bases of Exercise. Received D 2. and B.DECEMBER 1993 Downloaded from advan. H. Collins 7 January 1993.. O. 4. Arm exercise training for wheelchair users. Sci. and the questions will make the discussion thought provoking. Dis. 1992.physiology. Horace Smirk 1902-1991: exercise physiologist. suppl. Blomqvist. J. 1991. 67. PA: Lea & Febiger. Sparks. Rodahl. DiCarlo. G. p. Respir. Rowe& cal Stress. M. M. M. and 3 h to complete. Med. This would stimulate an exchange of information. A. Acad. N . New York: Oxford University Press. Unethical alterations of oxygen-carrying capacity in endurance athletes. and I. Shephard. F. Sci. Case.ADVANCES IN PHYSIOLOGY s31 EDUCATION . NIPS 4: 143-146.: S13-S16. 1992. of Physiology. Sport. C. Human Circulation Regulation During Physi3. S. paper. Y. Am. Responses of the cardiac transplant patient to exercise and training. Cardiovascular response and control during exercise. NIPS 6: 199. Segal. Teachers and their students may find the following articles from News in Physiological Sciences useful when exploring the physiology of the preceding paper: Bove. Astrand. Pbysiol. Address for reprint reyuests: S. Rootstown. Sports Exercise 21: S149-S157. A. 1983. W. M. Northeastern Ohio Universities. an interest in cardiovascular physiology.1984. accepted in final form I D E A Suggested Readings in 16 June 1993. 1. 1986. Textbook of Work Physiology. and D. References NIPS S R. Swanson. Glaser. B. Gorman. B. 1986. (Editor). It requires pencils. P. 6: 191-193. S. J. Guidelines for Exercise Testing and Prescription/American College of Sports Medicine (4th ed. 129. Rowe& cal Stress. work of Heidi L. College of Medicine. Rev. Pate. J.1992. Relationship between scores on NBME basic science subject tests and the first administration of the newly designed NBME part I examination. Philadelphia.1992. 3. Communication among endothelial and smooth muscle cells coordinates blood flow control during exercise. 1989. Becker. NIPS 7: 88-89.. 45: 169-89. 1991. Ann. Cardiovascular adaptations to physical training. 2012 1. V. Human Circulation Regulation During Pbysi3. NIPS 3: 241-244. Stone. Stray-Gunderson. 20: 297-320. New York: McGraw-Hill. 1988. S.org on April 16. L. R. Hormonal responses to acute and chronic exercise. E. and H. 1991. VOLUME IO : NUMBER I . Exert. Athlete’s heart. PO Box 95. L. Rev. S. Med. D. Liang. L.