Atenção:

1. Atenção: Recomendamos o material a seguir apenas com o objetivo de divulgar materiais de qualidade e que estejam disponíveis gratuitamente. Profa. Cristina Maria Henrique Pinto CFS/CCB/UFSC O presente arquivo é uma coletânea de figuras e textos extraídos da coleção em CD-ROM utilizada em nossas aulas. “Interactive Physiology”, da Benjamin Cummings.

2. Você pode também dar baixa destes resumos dos CD-ROM´s, não apenas de Cardiovascular mas de diversos outros assuntos de Fisiologia Humana (arquivos em *.pdf e/ou *.doc), com textos e ilustrações, diretamente do site: Selecione: “assignments”em: http://www.aw-bc.com/info/ip/ e escolha entre os seguintes assuntos: Muscular; Nervous I; Nervous II; CardiovascularRespiratory; Urinary; Fluids & ElectrolytesEndocrine e Digestive(novos) Veja também aulas online (DEMO dos CD-ROM´s) sobre: Endocrine topics eDigestive system (recém-lançados)

3. Cardiovascular Physiology parte 3: Factors that Affect Blood Pressure, Cardiac Cycle, Cardiac Output Profa. Cristina Maria Henrique Pinto - CFS/CCB/UFSC monitores: Vinicius Negri Dall'Inha e Grace Keli Bonafim (graduandos de Medicina) Este arquivo está disponível em: http://www.cristina.prof.ufsc.br/md_cardiovascular.htm

4. Factors that Affect Blood Pressure Graphics are used with permission of: Pearson Education Inc., publishing as Benjamin Cummings (http://www.aw-bc.com) Introduction • Blood pressure is affected by several factors: • peripheral resistance • vessel elasticity • blood volume • cardiac output • As you go through this topic, keep in mind this flow chart, which outlines the factors affecting blood pressure: Goals • To understand the factors that affect peripheral resistance, and therefore blood pressure. • To understand how vessel elasticity, blood volume, and cardiac output affect blood pressure. Sources of Peripheral Resistance • One of the main factors that affects blood pressure is peripheral resistance. • Blood cells and plasma encounter resistance when they contact blood vessel walls. • If resistance increases, then more pressure is needed to keep blood moving. • Three main sources of peripheral resistance: 1. blood vessel diameter 2. blood viscosity 3. total vessel length

5. Vessel Diameter Analogy • Vessel diameter affects peripheral resistance. • As a the diameter of a tube gets smaller, a greater proportion of the fluid is in contact with the wall of the tube. Therefore resistance to flow is increased and pressure rises. • Larger diameter, same volume, less pressure. • Smaller diameter, same volume, more pressure. Vasomotor Fibers • Constriction of blood vessels raises blood pressure. • Vessel diameter is actively regulated by vasomotor fibers, sympathetic nerve fibers that innervate the vessel's smooth muscle layer. • Vasomotor fibers release norepinephrine, a powerful vasoconstrictor. • A vasoconstrictor is a substance that causes blood vessels to constrict.

6. Epinephrine Angiotensin II Vasopressin Vasoconstrictors • Blood vessel diameter is also regulated by blood-borne vasoconstrictors. • Record the effect of each of these chemicals on the blood vessel: Viscosity Demonstration • Blood viscosity affects peripheral resistance. • Viscosity is related to the thickness of a fluid. • The greater the viscosity, the less easily molecules slide past one another and the more difficult it is to get the fluid moving and keep it moving. • Because of this greater resistance to flow, a greater pressure is required to pump the same volume of viscous fluid.

7. Blood Viscosity • The hematocrit is the percentage of red blood cells in the total blood volume. • The hematocrit affects blood viscosity and therefore resistance to flow. • The more viscous the blood, the greater resistance it encounters and the higher the blood pressure. • The hematocrit can increase when there are more red blood cells or less plasma in the blood. • The hematocrit can decrease when there are fewer red blood cells or more plasma. Vessel Length • Total vessel length affects peripheral resistance. • Increased fatty tissue requires more blood vessels to service it and adds to the total vessel length in the body. • The longer the total vessel length, the greater the resistance encountered, and the greater the blood pressure. • When an individual has arteriosclerosis, arteries become calcified and rigid, so they can't expand when the pulse wave of systolic pressure passes through them. Thus the walls of the artery experience higher pressures and become weaker and weaker.

8. Vessel Elasticity • Besides peripheral resistance, blood vessel elasticity also affects blood pressure. • A healthy elastic artery expands, absorbing the shock of systolic pressure. The elastic recoil of the vessel then maintains the continued flow of blood during diastole. • When an individual has arteriosclerosis, arteries become calcified and rigid, so they can't expand when the pulse wave of systolic pressure passes through them. Thus the walls of the artery experience higher pressures and become weaker and weaker. Blood Volume Analogy: Hoses • Blood volume affects blood pressure. • When there is a greater volume of fluid, more fluid presses against the walls of the arteries resulting in a greater pressure. • When there is less volume there is less pressure. Blood Volume Examples • Reduced blood volume (for example due to excessive sweating) reduces blood pressure short term. Long term homeostatic mechanisms compensate, bringing blood volume and blood pressure back up to normal levels. • Increased blood volume (for example due to water retention from excessive salt intake) increases blood pressure short term. Long term homeostatic mechanisms compensate, bringing blood volume and blood pressure back up to normal levels.

9. Cardiac Output: Heart Rate • Anything that decreases cardiac output, also decreases blood pressure, because there is less pressure on the vessel walls. • An increase in cardiac output results in increased blood pressure. • Cardiac Output = Heart Rate X Stroke Volume • Anything that affects heart rate or stroke volume affects cardiac output and thus blood pressure. • What happens to heart rate, cardiac output, and blood pressure with parasympathetic stimulation (vagus nerve)? • What happens to heart rate, cardiac output, and blood pressure with sympathetic stimulation? Cardiac Output: Stroke Volume • Affect of stroke volume on blood pressure. • If less blood is ejected from the heart with each beat, then blood pressure will be lower because there will be less blood pressing against the vessel walls. • Blood volume affects end diastolic volume and therefore stroke volume. • With decreased stroke volume, due to decreased venous return, volume there is a decreased cardiac output and a decreased blood pressure. • With increased stroke volume, due to increased venous return and/or increased contractility, there is an increased cardiac output and increased blood pressure. Summary • Increases in peripheral resistance, blood volume, and cardiac output result in higher blood pressure. Conversely decreases in any of these factors lead to lower blood pressure. • Three main sources of peripheral resistance: Blood vessel diameter, blood viscosity, and total vessel length. • If arteries lose their elasticity and become more rigid, blood pressure increases.

10. Study Questions on Factors that Affect Blood Pressure: 1. (Page 1.) What are the four main factors affecting blood pressure? 2. (Page 3.) Blood cells and plasma encounter resistance when they contact blood vessel walls. What is this resistance called? 3. (Page 3.) Is more or less pressure needed to keep blood moving when resistance increases? 4. (Page 3.) What are the three main sources of peripheral resistance? 5. (Page 4.) What is the relationship between the diameter of a tube and the proportion of fluid that is in contact with the wall of the tube? 6. (Page 4.) What is the relationship between the diameter of a tube and resistance to flow? What effect does this have on pressure? 7. (Page 5.) Does constriction of blood vessels raise or lower blood pressure? 8. (Page 5.) What actively regulates the diameter of blood vessels? 9. (Page 5.) What chemical is released by vasomotor fibers that acts as a powerful vasoconstrictor? 10. (Page 6.) List three blood-borne vasoconstrictors? 11. (Page 7.) Explain viscosity. 12. (Page 7.) What is the relationship between viscosity and pressure required to pump a fluid? 13. (Page 8.) Define hematocrit. 14. (Page 8.) What is the effect of hematocrit on blood viscosity? 15. (Page 8.) When does hematocrit increase? 16. (Page 9.) What is the relationship between the total vessel length, resistance, and blood pressure? 17. (Page 10.) Why is expansion and recoil of the elastic arteries important? 18. (Page 10.) Why does blood pressure often increase in individuals with arteriosclerosis? 19 (Page 11.) What is the relationship between blood volume and blood pressure? 20. (Page 13.) What is the relationship between blood pressure and cardiac output?

11. 21. (Page 13.) What is the relationship between heart rate, stroke volume and cardiac output? 22. (Page 13.) What happens to heart rate, cardiac output, and blood pressure with both parasympathetic and sympathetic stimulation? 23. (Page 14.) What is the relationship between venous return and stroke volume?

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13. The Cardiac Cycle Graphics are used with permission of: adam.com (http://www.adam.com/) Benjamin Cummings Publishing Co (http://www.awl.com/bc) Introduction • The cardiac cycle includes all the events related to the flow of blood through the heart during one complete heartbeat. Goals • To list the phases of the cardiac cycle in consecutive order. • To recognize that the pressure changes determine valve action and direction of blood flow through the heart. • To relate an ECG and heart sounds to events of the cardiac cycle. Heart Valves • During the cardiac cycle, heart valves open and close in response to differences in blood pressure on their two sides. • The Heart Valves: • Pulmonary semilunar valve • Aortic Semilunar Valve • Left AV valve or Bicuspid valve or Mitral valve • Right AV valve or Tricuspid valve Overview of Cardiac Cycle • Phases of the Cardiac Cycle 1. Ventricular Filling - Occurs during mid to late diastole. 2. Ventricular Systole - Includes isovolumetric contraction and ventricular ejection. 3. Isovolumetric Relaxation - Occurs during early diastole.

14. Ventricular Filling: Passive • Occurs during mid to late diastole, when the heart chambers are relaxed. • Blood flows passively into the atria, through open AV valves, and into the ventricles, where the pressure is lower. Ventricular Filling: Atrial Contraction • Atria contract, forcing the remaining blood into the ventricles. • Blood flows through both sides of the heart at the same time. Ventricular Systole: Contraction • Isovolumetric contraction: Ventricles contract and intraventricular pressure rises, closing the AV valves. Briefly, ventricles are completely closed chambers. Ventricular Systole: Ejection • Ventricular ejection: Rising ventricular pressure forces semilunar valves open. Blood is ejected from the heart into the aorta and pulmonary trunk. Isovolumetric Relaxation • Ventricles relax and ventricular pressure drops. Blood backflows, closing semilunar valves. Ventricles are totally closed off again. Atrial Filling • Meanwhile, the atria have been filling with blood. When atrial pressure exceeds ventricular pressure, AV valves open and ventricular filling, phase 1 begins again. Ventricular and Atrial Contraction • Although we have been highlighting the flow of blood on the right side of the heart, remember that both atria contract at the same time and both ventricles contract at the same time. Control of Blood Flow by Pressure • Pressure changes reflect the alternating contraction and relaxation of the heart. • Blood moves along a pressure gradient (from higher to lower pressure) through any available opening. • Pressure changes cause the heart valves to open and close, which keeps the blood flowing in the forward direction.

15. Overview: Graphs and Heart • During ventricular ejection phase, ventricular pressure rises higher than aortic pressure. This is necessary to open the semilunar valve. • Only a little more than half of the blood is ejected during ventricular ejection. Left Atrial Pressure

16. Left Ventricular Pressure Aortic Pressure Ventricular Volume ECG Notes on Quiz Questions: Quiz Question 1: Blood Flow through Heart • This question asks you to trace the blood through the right side of the heart. Quiz Question 2: Valves • This question asks you to predict when the valves are open or closed during the various stages of the cardiac cycle. Quiz Questions 3a, 4a, 5a, 6a: Cardiac Cycle Phase • These question asks you to view a diagram of the heart and predict what stage of the cell cycle it's in. You may take notes on the diagrams below. The dye-labeled blood has been colored light here to make it more visible. Quiz Question 3b, 4b, 5b, 6b: Cardiac Cycle Graphs • These questions asks you to predict the correct phase of the cardiac cycle by viewing an ECG, graph of ventricular volume, and a graph of pressures. You may want to take notes on this diagram:

18. 1a. Ventricular Filling: Passive v. Ventricles contract and intraventricular pressure rises, closing the AV valves. 1b. Ventricular Filling: Atrial Contraction w. Ventricles relax and ventricular pressure drops. Blood backflows, closing semilunar valves. 2a. Ventricular Systole: Isovolumetric Contraction x. Blood flows passively into the atria, through open AV valves, and into the ventricles. 2b. Ventricular Systole: Ejection y. Rising ventricular pressure forces semilunar valves open. Blood is ejected from the heart. 3. Isovolumetric Relaxation z. Atria contract, forcing the remaining blood into the ventricles. Study Questions on the Cardiac Cycle: 1. (Page 1.) What is a cardiac cycle? 2. (Page 3.) What opens and closes the heart valves? 3. (Page 4.) List the three phases of the Cardiac Cycle. 4. (Pages 5-10.) Match the stages of the cardiac cycle to their description.

19. 5. (Page 6.) True or false: Blood passes through the bicuspid valve at the same time blood is also passing through the tricuspid valve. 6. (Page 7.) What closes the AV valves? 7. (Page 8.) What opens the semilunar valves? 8. (Page 9.) What closes the semilunar valves? 9. (Page 10.) What opens the AV valves? 10. (Page 11.) True or false: The right side of the heart contracts, then the left side of the heart contract. 11. (Page 12.) What is the relationship between pressure inside a chamber of the heart and the state of the heart muscle (relaxed or contracted)? 12. (Page 12.) Blood always moves from ____ pressure to ____ pressure. 13. (Page 12.) What causes heart valves to open and close?

20. State of AV Valves State of Semilunar Valves Isovolumetric Contraction Open Closed Open Closed Isovolumetric Relaxation Open Closed Open Closed Ventricular Ejection Open Closed Open Closed Ventricular Filling Open Closed Open Closed 14. (Page 12.) Predict if the AV and semilunar valves are open or closed during the following phases of the cardiac cycle by circling the appropriate answer on this chart: 15. (Pages 14-19.) What is happening to the volume of blood inside the ventricles during each labeled part of the graph below? 16. (Pages 14-19.) What is happening to the pressure inside the ventricles during each labeled part of the graph below? Explain. 17. (Pages 14-19.) What is happening to the depolarization, repolarization and contraction of the atria and ventricles during each labeled part of the graph below?

21. 18. Pages 14-19.) On the graph below, which number corresponds to: ventricular ejection isovolumetric relaxation ventricular filling isovolumetric contraction

22. Cardiac Output Graphics are used with permission of: Pearson Education Inc., publishing as Benjamin Cummings (http://www.aw-bc.com) Introduction • Cardiac output is the amount of blood pumped out by each ventricle in one minute. • Cardiac output can increase markedly to meet the demands placed on our body, whether dashing to catch a bus or riding a mountain bike, Goals • To recognize that cardiac output varies directly with heart rate and stroke volume. • To identify factors that modify heart rate and stroke volume, and to indicate how they change cardiac output. Cardiac Output Definition • Cardiac Output (CO) = The volume of blood ejected from the left or right ventricle into the aorta or pulmonary trunk per minute. • Cardiac output depends on: 1. Heart rate 2. Stroke volume Cardiac Output = Heart Rate X Stroke Volume CO = HR X SV Heart Rate Definition • Heart rate (HR) is the number of times the heart beats in one minute, averaging 75 beats per minute (bpm) in the adult at rest. Stroke Volume Definition • Stroke volume (SV) is the amount of blood pumped by each ventricle with each heartbeat, averaging 70 ml per beat in the adult at rest.

23. SV = EDV - ESV • Stroke volume represents the difference between end diastolic volume (EDV) and end systolic volume (ESV). • By the time diastole ends, each ventricle has filled up with blood. This amount of blood is the end diastolic volume or EDV. • The amount of blood ejected during the systole is the stroke volume. At the end of systole the volume of blood remaining in each ventricle is the end systolic volume or ESV. • Each ventricle normally contains about 120 ml of blood by the end of diastole. At the end of systole about 50 ml of blood are left in each ventricle. This means that 70 ml of blood were pumped out of each ventricle during systole. Stroke Volume = End-Diastolic Volume - End-Systolic Volume SV = EDV - ESV ~70 ml/beat= ~ 120 ml/beat - ~50 ml/beat Regulation of Cardiac Output • The key factor regulating stroke volume is the amount of stretching that occurs to ventricular cardiac muscle prior to ventricular contraction. The more cardiac muscle stretches, the more forcefully it contracts. These stronger contractions increase stroke volume.

24. Affect on Heart Rate Affect on Stroke Volume Affect on Cardiac Output Increased Sympathetic Stimulation Increased Parasympathetic Stimulation Increased Venous Return Slow Heart Rate Extremely Fast Heart Rate Exercise Sudden Drop in Blood Pressure Rising Blood Pressure Sudden Drop in Blood Volume Excess Calcium • Fill out this chart, making note of the reasons for the increase or decrease:

25. • Increased Sympathetic Stimulation - Increased sympathetic stimulation (due to fright, anger, etc.) increases the heart rate. It also increases stroke volume by increasing contractility, which results in more complete ejection of blood from the heart (lower ESV). • Increased Parasympathetic Stimulation - Parasympathetic activity increases after a crisis has passed. This reduces heart rate and stroke volume from their high levels, bringing cardiac output back to normal. • Increased Venous Return - Cardiac muscle fibers are stretched by increased blood volume returning to the heart (increased venous return and EDV). Increased stretch results in greater force of contraction, which increases stroke volume. • Slow Heart Rate - Slow heart rate allows for more time for ventricular filling, increasing EDV and therefore stroke volume. • Extremely Fast Heart Rate - Extremely rapid heart rate results in low venous return and therefore decreased stroke volume. • Exercise - Exercise activates the sympathetic nervous system, increasing heart rate, contractility, and stroke volume. Both the higher heart rate and squeezing action of skeletal muscles on veins increase venous return, contributing to increased stroke volume. • Sudden Drop in Blood Pressure - A sudden drop in blood pressure results in low venous return and therefore decreased stroke volume. However heart rate increased due to sympathetic activity, and normal cardiac output is maintained. • Rising Blood Pressure - Rising blood pressure reduces sympathetic activity, decreasing heart rate. High blood pressure also increases arterial pressure which ventricles must overcome before semilunar valves open, increasing ESV and decreasing stroke volume. Reduced cardiac output helps bring blood pressure down to normal levels. • Sudden Drop in Blood Volume - A sudden drop in blood volume (eg. due to severe blood loss) results in low venous return and therefore decreased stroke volume. Sympathetic activity increases heart rate, maintaining cardiac output. • Excess Calcium - Excess calcium can lead to spastic heart contractions, an undesirable condition. Calcium also increases stroke volume by enhancing contractility. Heart Videos • Effect of Epinephrine on a Frog's Heart: Epinephrine is normally released when there is increased sympathetic activity. • Effect of Acetyl Choline on a Frog's Heart: Acetyl choline is a parasympathetic neurotransmitter. Summary • Cardiac Output = Heart Rate X Stroke Volume • Heart rate is increased by sympathetic nerve activity and epinephrine. Heart rate is decreased by parasympathetic nerve activity.

26. Study Questions on Cardiac Output: 1. (Page 3.) Define cardiac output. 2. (Page 3.) What two factors does cardiac output depend on? 3. (Page 3.) What is the mathematical relationship between cardiac output, heart rate, and stroke volume. 4. (Page 4.) Define heart rate. 5. (Page 4.) What is the average heart rate in an adult at rest? 6. (Page 5.) Define stroke volume. 7. (Page 5.) What is the average stroke volume in an adult at rest? 8. (Page 6.) Define end diastolic volume. 9. (Page 6.) Define end systolic volume. 10. (Page 10.) What is the mathematical relationship between end diastolic volume, end systolic volume, and stroke volume? 11. (Page 6.) If the ESV is 50 ml and the EDV is 120 ml, what is the stroke volume? 12. Page 7.) If the heart rate is 75 beats per minute and the stroke volume is 70 ml per beat, then what is the cardiac output? 13. (Page 8.) What's the relationship between cardiac muscle stretch and force of contraction? What effect does this have on stroke volume?

27. 14. (Page 8.) What's the relationship between venous return and stroke volume? 15. (Page 8.) What is the effect of increased sympathetic activity on heart rate and stroke volume? How does this effect cardiac output? 16. (Page 8.) What is the effect of increased parasympathetic activity on heart rate and stroke volume? 17. (Page 8.) What is the effect of increased venous return on heart rate and stroke volume? How does this effect cardiac output? 18. (Page 8.) What effect does a slow heart rate have on stroke volume? 19. (Page 8.) What effect does a fast heart rate have on stroke volume? 20. (Page 8.) What is the effect of exercise on heart rate and stroke volume? How does this effect cardiac output? 21. (Page 8.) What is the relationship between blood pressure and sympathetic activity? What effect does this have on heart rate? 22. (Page 8.) What is the effect of a sudden decrease in blood pressure on heart rate and stroke volume? 23. (Page 8.) What is the effect of a sudden increase in blood pressure on heart rate? 24. (Page 8.) What is the effect of a sudden increase in blood pressure on stroke volume? 25. (Page 8.) What is the effect of a sudden drop in blood volume on heart rate and stroke volume? 26. (Page 8.) What is the effect of an increase in calcium on heart rate and stroke volume?

28. Cardiovascular Physiology continua em: parte 4: Blood Pressure Regulation and Autoregulation and Capillary Dynamics parte 1: Anatomy review: the heart, anatomy review: blood vessel and structure and function parte 2: Intrinsic Conduction System, Measuring Blood Pressure and Cardiac Action Potential Profa. Cristina Maria Henrique Pinto - CFS/CCB/UFSC monitores: Vinicius Negri Dall'Inha e Grace Keli Bonafim (graduandos de Medicina) Este arquivo está disponível em: http://www.cristina.prof.ufsc.br/md_cardiovascular.htm