* Where is your heart and what does it look like? * Your coronary arteries * How does the heart beat? * How does blood flow through the heart? * How does blood travel through your body? * Heart Facts * Simple Clues to Your Heart * Illustrations of the heart * Illustrations of the Blood Vessels * Heart and Vascular Health & Prevention The heart is located under the rib cage, to the left of the breastbone (sternum) and between the lungs. Your heart is an amazing organ. Shaped like an upside-down pear, this fist-sized powerhouse pumps five or six quarts of blood each minute to all parts of your body. Outside the heart Looking at the outside of the heart, you can see: * that the heart is made of muscle. The strong muscular walls contract (squeeze), pumping blood to the arteries. * the major blood vessels that enter the heart: o aorta o superior vena cava o inferior vena cava o pulmonary artery takes oxygen-poor blood from the heart to the lungs o pulmonary vein -- brings oxygen-rich blood from the lungs to the heart o the coronary arteries Inside the heart The heart is a four-chambered, hollow organ. Get a larger view It is divided into the left and right side by a muscular wall called the septum. The right and left sides of the heart are further divided into: * two atria - top chambers, which receive blood from the veins and * two ventricles - bottom chambers, which pump blood into the arteries The atria and ventricles work together, contracting and relaxing to pump blood out of the heart. The normal aortic valve As blood leaves each chamber of the heart, it passes through a valve. There are four heart valves within the heart: * mitral valve * tricuspid valve * aortic valve * pulmonic valve (also called pulmonary valve) The tricuspid and mitral valves lie between the atria and ventricles. The aortic and pulmonic valves lie between the ventricles and the major blood vessels leaving the heart. The heart valves work the same way as one-way valves in the plumbing of your home, preventing blood from flowing in the wrong direction. The normal mitral valve Get a larger view Each valve has a set of flaps, called leaflets or cusps. The mitral valve has two leaflets; the others have three. The leaflets are attached to and supported by a ring of tough, fibrous tissue called the annulus. The annulus helps to maintain the proper shape of the valve. The leaflets of the mitral and tricuspid valve are also supported by tough, fibrous strings called chordae tendineae. These are similar to the strings supporting a parachute. The chordae tendineae extend from the valve leaflets to small muscles, called papillary muscles, which are part of the inside walls of the ventricles http://my.clevelandclinic.org/heart/disorders/cad/cad_arteries.aspx 1# Blockage of which of the following arteries would lead to ischemia of the apex of the heart? Anterior interventricular (descending) Left circumflex Posterior interventricular (descending) Right marginal Right coronary 2# If the ductus arteriosus does not spontaneously close off soon after birth (to become the ligamentum arteriosum), it may have to be surgically ligated. When clamping or ligating it, what important structure immediately behind it must be identified and saved? arch of the azygos vein internal thoracic artery left phrenic nerve left recurrent laryngeal nerve left superior intercostal vein 3# A hand slipped behind the heart at its apex can be extended upwards until stopped by a line of pericardial reflection that forms the: Cardiac notch Costomediastinal recess Hilar reflection Oblique pericardial sinus Transverse pericardial sinus 4# A stethoscope placed over the left second intercostal space just lateral to the sternum would be best positioned to detect sounds associated with which heart valve? aortic pulmonary mitral tricuspid 5# Which valves would be open during ventricular systole? Aortic and pulmonary Aortic and tricuspid Mitral and aortic Tricuspid and mitral Tricuspid and pulmonary Answer:A 6# Which chamber's anterior wall forms most of the sternocostal surface of the heart? Left atrium Left ventricle Right atrium Right ventricle 7# A 3rd-year medical student was doing her first physical exam. In order to properly place her stethoscope to listen to heart sounds, she palpated bony landmarks. She began at the jugular notch, then slid her fingers down to the sternal angle. At which rib (costal cartilage) level were her fingers? 1 2 3 4 8# A patient involved in an automobile accident presents with a sharp object puncture of the middle of the sternum at about the level of the 4th or 5th costal cartilage. If the object also penetrated pericardium and heart wall, which heart chamber would most likely be damaged? Left atrium Left ventricle Right atrium Right ventricle 9# Which statement is true of the right atrioventricular valve? it is also called the mitral valve it is open during ventricular diastole it transmits oxygenated blood it is opened by the pull of chordae tendineae it consists of 2 leaflets 10# A 23-year-old male injured in an industrial explosion was found to have multiple small metal fragments in his thoracic cavity. Since the pericardium was torn inferiorly, the surgeon began to explore for fragments in the pericardial sac. Slipping her hand under the heart apex, she slid her fingers upward and to the right within the sac until they were stopped by the cul-de-sac formed by the pericardial reflection near the base of the heart. Her fingertips were then in the: Coronary sinus Coronary sulcus Costomediastinal recess Oblique sinus Transverse sinus 11# An elderly lady suffers a coronary occlusion and subsequently it is noted that there is a complete heart block (that is, the right and left bundles of the conduction system have been damaged). The artery most likely involved is the: acute marginal branch circumflex branch anterior interventricular (Left anterior descending) obtuse marginal posterior interventricular (posterior descending) 12# During fetal life and sometimes persisting into the adult there is an opening between the right and left atria; this opening is called the: atrioventricular canal coronary sinus foramen ovale sinus venosus truncus arteriosis 13# The heart sound associated with the mitral valve is best heard: In the jugular notch In the second left intercostal space In the second right intercostal space In the fifth left intercostal space To the right of the xiphoid process 14# Which heart valve has leaflets described as "anterior, left and right"? Aortic Pulmonary Left atrioventricular Right atrioventricular 15# In preparation for thoracic surgery, a median sternal splitting procedure was carried out. But an improper depth setting on the saw blade resulted in a slight nick on the underlying sternocostal surface of the heart. Which heart chamber would most likely have been opened had the blade completely penetrated this wall? Left atrium Left ventricle Right atrium Right ventricle 16# The sound associated with tricuspid stenosis (narrowing) in a 40-year-old male would be best heard at which location on the anterior chest wall? Below the left nipple In the right 2nd intercostal space near the sternum Over the apex of the heart Over the sternal angle Xiphoid area, just off the sternum 17# Blockage of blood flow in the proximal part of the anterior interventricular artery could deprive a large area of heart tissue of blood supply, unless a substantial retrograde flow into this artery develops via an important anastomosis with which other artery? Circumflex Left marginal Posterior interventricular Right coronary Right marginal 18# Traumatic, acceleration/deceleration injuries to the aorta usually occur where its mobile and fixed portions meet. This would be at the: at the ligamentum arteriosum junction of aortic arch with the descending portion junction of the ascending aorta with the heart origin of the brachiocephalic artery on the arch point where the descending aorta passes through the diaphragm 19# Which structure does NOT lie in the coronary sulcus? circumflex artery coronary sinus right coronary artery right marginal artery left coronary artery 20# Which structure contains postganglionic sympathetic fibers? greater thoracic splanchnic nerve recurrent laryngeal nerve sympathetic trunk ulnar nerve vagus nerve 21# Which posterior mediastinal structure is most closely applied to the posterior surface of the pericardial sac? Aorta Azygos vein Esophagus Thoracic duct Trachea 22# In obstruction of the superior or inferior vena cava, venous blood is returned to the heart by an alternate route via the azygos vein, which becomes dilated in the process. Which of the following structures might it compress as a result? trachea root of the left lung phrenic nerve thoracic duct descending aorta 23# Elevated systolic blood pressure in the right ventricle suggests stenosis of which valve? Aortic Mitral Pulmonary Tricuspid 24# During examination of a 62-year-old man, the senior resident tells you to put your stethoscope on the left 5th intercostal space, slightly below the nipple, and listen for a clearly audible murmur. You hear it distinctly and know it must be associated with severe stenosis of which heart valve? Aortic Mitral Pulmonary Tricuspid 25# A 26-year-old male is brought into the emergency room after having been kicked in the chest by a horse. After examination, it is concluded that the most likely immediate danger is cardiac tamponade (bleeding into the pericardial sac). You prepare to draw off some of the blood from the sac to relieve the pressure on the heart. The safest site at which to insert the needle of the syringe in order to miss the pleura would be: Just below the nipple on the left Just to the left of the xiphisternal junction Near the sternal angle Through the jugular notch 4th left intercostal space in the midaxillary line 26# A 22-year-old male involved in an automobile accident presents with symptoms suggestive of myocardial contusion due to blunt trauma, specifically compression of the sternocostal surface of the heart by the sternum when his chest hit the steering wheel. Which heart chamber was most likely damaged? Left atrium Left ventricle Right atrium Right ventricle 27# While attempting to suture the distal end of a coronary bypass onto the anterior interventricular artery, the surgeon accidentally passed the needle through the adjacent vein. Which vein was damaged? Anterior cardiac vein Coronary sinus Great cardiac vein Middle cardiac vein Small cardiac vein 28# While listening to a patient's heart sounds with a stethoscope, you identify a high-pitched sound in the second right intercostal space, just lateral to the edge of the sternum. Your correct conclusion is that you have detected stenosis of which heart valve? Aortic Mitral Pulmonary Tricuspid http://anatomy.med.umich.edu/cardiovascular_system/heart_questions.html Be able to distinguish anatomical and molecular structures of skeletal muscles and cardiac muscles, including sarcomeres, intercalated discs, gap junctions, Z-lines, actin, myosin, troponin, tropomyosin, nebulin and titin, RyR, transverse tubules, Ca-ATPase (PMCA and SERCA), phospholamban, Na/Ca exchanger. Be able to describe the interactions between Ca and Tn that give rise to control of skeletal and cardiac muscle contraction. Compare this to control of smooth muscle contraction by Ca and myosin light chain kinase. How do all the muscles relax? Distinguish among the following types of skeletal muscles: fast twitch, glycolytic; fast twitch oxidative; slow twitch oxidative. Mention size, aerobic vs anaerobic mechanisms for generating ATP, presence of myoglobin and mitochondria. 1. T or F? Skeletal muscle cells have more than one nucleus. 2. The modified endoplasmic reticulum in skeletal and cardiac muscle is called the ___, and it actively accumulates ___ during the relaxation phase. 3. Ca permeability of the plasma membrane of the three different types of muscle cells is in the order __ and __ >> ___. 4. T-tubules allow __ to move to the interior regions of skeletal and cardiac muscle. 5. If a heart cell had a genetic defect in its titin molecules such that its normal function was altered, how might this affect heart function? 6. Which of the following is an ATPase? G-actin, F actin, myosin, myosin light chain, titin, troponin 7. Inositol trisphosphate receptors are found in __ muscle cells, while ryanodine receptors are found in __ muscle cells. 8. Explain the differences between twitch, summation, and tetanus, and also why skeletal muscle exhibits tetanic contractions but cardiac muscle does not. 9. Describe the interactions between actin and myosin during contraction and relaxation, i.e., the sliding filament model. 10. Which type of muscle is the most efficient in terms of generating force for a given amount of ATP? Which type of muscle contracts the most slowly? 11. What determines different forces involved in picking up a pencil vs picking up a 10 pound weight? 12. Curare is a poison that paralyzes muscles without affecting release of acetylcholine. The muscles can still contract if an electrical stimulus is applied directly to the muscle. What does curare do? 13. A muscle was experimentally put into a rigor state by removal of ATP (with a method that allows access to the insides of the cells). What would happen to the muscle if ATP were added in the presence vs the absence of Ca? 14. T or F? Fatigue of cardiac muscle is caused when [ATP] decreases to zero. Review Questions | Coordinated activities of heart and blood vessels Define: P-V loop, systole and diastole; ventricular filling; atrial contraction; isovolumetric ventricular contraction; ventricular ejection (how much is ejected?); isovolumetric ventricular relaxation. Be able to locate these aspects of cardiac function on a "pressure-volume loop." Also, calculate stroke volume and "ejection fraction" from the diagram. Describe the structure of the heart, including chambers, valves, major vessels entering and leaving, as well as endo-, epi- and myocardium, valves, papillary muscles, chordae tendinae, SA and AV nodes, Purkinje fibers, coronary blood supply. How is valve structure related to valve function? Indicate the sequential participation of specific heart valves during the above pumping cycle. 1. What would happen to cardiac muscle contractility and excitability in the presence of drugs that specifically block Ca channels in the plasma membrane? 2. Name the different functions of ATP during normal contractile cycle of the heart. 3. Caffeine causes the RyR to release Ca and also has effects on cAMP metabolism (see signaling). What might caffeine do to the heart's contraction? 4. Offer explanations for why epinephrine increases: contraction strength and rate of relaxation. 5. Why can't the heart contract tetanically? 6. Which of the following causes Na channels in heart muscle to open? a. Hyperpolarization b. depolarization c. increases in cell Ca d. activation of the acetylcholine receptor 7. What provides nutrition to the heart muscle cells? a. blood in the atria and ventricles b. pulmonary artery c. pulmonary vein d. coronary blood vessels e. none of the above. Why is does a heart attack occur when this blood supply is blocked? What blood components are analyzed to determine whether a patient has had a heart attack? 8. T or F? Cardiac action potentials proceed in the sequence: atria, SA node, bundle of His, AV node, ventricles 9. Why is it so disastrous to the heart to elevate extracellular [K] very rapidly? Explain in terms of voltage-dependent Na channels, K channels, membrane voltage, activation and inactivation. 10. What is difference between single-unit and multi-unit smooth muscle? 11. How are smooth muscle and cardiac muscle different in terms of their requirement for electrical excitation before contraction? 12. How do the neurotransmitters norepinephrine and acetylcholine affect cardiac vs smooth muscle? 13. T or F? Cutting the vagus nerve causes the heart to speed up. Explain your answer. 14. T or F? End diastolic volume is equal to about 150 ml, and end systolic volume is about 0 ml, so the stroke volume equals 150 ml. 15. T or F? Stroke volume of the left ventricle is larger than that of the right ventricle. Review Questions | Hemodynamics and Vessel Functions Define: Diffusion and bulk flow; Poiseuille's law (also how flow in CV system is related to pressure difference and resistance); systemic and pulmonary circulations; cardiac output and relationship to stroke volume and heart beat rate; aorta, arteries, arterioles, capillaries, veins; main structural and functional differences between arteries, arterioles, capillaries and veins; change in velocity, pressure and area as traverse CV system; Law of Laplace; resistance to blood flow, peripheral resistance; compliance; venous valves Review the relative internal diameters, wall thickness, and amounts of the principal components of the various blood vessels and indicate functional implications of such composition. 1. 1. During exercise cardiac output often increases by 2 - 4 fold, but mean arterial pressure often exhibits no increase. In terms of cardiac output and peripheral resistance, explain this effect. 2. If resistance of vessels supplying the gastrointestinal tract increases, explain what would happen (assuming no other changes in the system) to blood flow in vessels of the GI tract and to mean arterial pressure. 2. Matching. a. arterioles b. arteries c. capillaries d. veins e. aorta i. store pressure generated by the heart ii. have walls that are stiff and elastic iii. carry low oxygen blood iv. have endothelial lining v. act as a volume reservoir vi. blood flows slowest here vii. have lowest blood pressure viii. sites of variable resistance ix. have large compliance x. blood flows fastest here 3. Aortic pressure reaches a high of ~__ mm Hg, also called the ___ pressure, and a low of ~__ mm Hg, also called the ___ pressure. 4. If an arteriole contracted such that its diameter was reduced by a factor of 2, what would be magnitude of change in blood flow through the vessel? Assume pressure remained constant. 5. The net flux of a solute that moves by passive diffusional mechanism is: a. a linear function of area available for diffusion. b. a linear function of the concentration difference for the solute across the barrier. c. directly proportional to the distance of diffusion. 6. For a skeletal muscle cell, [Ca] must rise in all parts of the cell within 200 msec. What is the maximum radius that would allow diffusion of Ca from the plasma membrane to the center of the cell to accommodate this requirement? Assume diffusion coefficient for Ca is 10–5cm2/sec. Use the Einstein equation: (Dx)2 = 2Dt. 7. Calculate the pressure declines and resistances of the arteries, arterioles, capillaries and veins. 8. Be able to locate the following in the CV system: aorta, arterioles, capillary beds, venules, veins, right atrium, right ventricle, left atrium, left ventricle. What are the two major circuits (circulations) of the CV system? Name three general differences between the two major circuits. 9. Sketch curves of approximate pressure, velocity of flow, cross-sectional area, and capacity of the blood vessels of the sytemic circulation (from aorta to venae cavae). Is there a pressure gradient between the aorta and arteries? Where is the pressure gradient the greatest in the systemic circulation? Why? 10. An artery was cannulated and attached to a thin glass tube. If systolic/diastolic pressures were 120 mm Hg/80 mm Hg, how high did the column of blood rise above the person's heart during these two phases of the heart cycle? 1 cm H20 = 0.74 mm Hg. 11. What is pulse pressure? 12. What is turbulent vs laminar flow, and how is turbulent blood flow used to measure blood pressure? 13. What is Law of Laplace, and why is it important for capillaries vs arterioles? How do Law of Laplace and Starling's Law of the Heart tend to counteract each other in the contraction of the heart? 14. Where is the transmural pressure greatest in a standing person? Left ventricle, aorta at the level of the kidney or artery in the brain? What happens when the person lies down? Explain. 15. Graph the pressure (x axis) - volume (y axis) relationship for an artery and vein and state the relative compliances of the arterial and venous systems. Review Questions | Capillary exchange: diffusion and osmosis, lymphatics and edema 1. Explain the roles of filtration and osmosis in determining direction of fluid flow across capillary walls during protein deficiency. 2. What happens to capillary fluid pressure when precapillary sphincter muscle controlling blood flow into the capillary bed dilates? 3. Which of the following is/are important in determining flux of oxygen from capillaries to muscles? a. oxygen concentration in the muscles b. oxygen concentration in the capillaries c. carbon dioxide concentration in the muscles d. colloid osmotic pressure of plasma e. hydrostatic pressure of the capillaries f. rate of blood flow through the capillaries g. distance from capillary to the muscle cells h. diameter of the capillary 4. Which of the following is not found in capillaries? a. smooth muscle b. valves c. endothelial cells d. basal lamina e. elastin f. tight junctions 5. What pressure forces are involved in causing lymph flow from the feet to return to the veins? 6. What type of transport (diffusion or osmosis or filtration) is important for delivery of the following substances across the capillary walls? a. glucose b. oxygen c. carbon dioxide d. proteins e. amino acids f. lactic acid g. water 7. Explain the significance of the following statement: total osmotic pressure of plasma is much larger than the colloid osmotic pressure. Review Questions | Regulation of blood pressure and flow Define: Frank-Starling mechanism; increased venous return due to muscle pump and respiratory pump; regulation of heart by sympathetic (including epinephrine) and parasympathetic nerves, including effects on rate of contraction and strength of contraction; local control of blood vessels due to myogenic mechanism (nitric oxide?) and metabolic regulation; regulation of arterioles by sympathetic and parasympathetic nerves; roles of blood volume, peripheral resistance and compliance in determination of arterial blood pressure and pulse pressure; baroreceptors (location and afferent nerves); cardiovascular center; "local control" (self-regulation or autoregulation) and metabolic regulation of arteriolar resistance in tissue beds and reflex control during hemorrhage; nerve fibers that innervate the heart, cardiac cells innervated, neurotransmitters released and receptors involved. 1. What is the advantage of regulation in which increased flow velocity leads to release of nitric oxide from endothelial cells? 2. What role does the Frank-Starling relationship play in normal physiology of the heart? What is contractility and how is it altered by sympathetic nerves? 3. What is the equation relating cardiac output and total peripheral resistance to mean arterial pressure? How do stroke volume and arterial compliance contribute to pulse pressure? 4. Do arterioles receive a supply of sympathetic nerve fibers? What neurotransmitter is released and what receptors are present in arteriolar smooth muscle? Do blood vessels in the brain and coronary circulation respond to sympathetic stimulation? Are arterioles innervated by parasympathetic nerves? What effect is observed when epinephrine binds to the alpha receptor in most vascular beds? What is the effect on skeletal muscle arterioles (why)? 5. There can be competition between local control dilation and sympathetic vasoconstriction. Which response most often predominates (particularly in brain and heart)? 6. What and where are baroreceptors? What is the routing of their information such that ultimately the sympathetic and parasympathic nerves are involved? What is the information content of the baroreceptor signals? 7. During response to hemorrhage, which of the following is increased, decreased or no change? 1. total peripheral resistance 2. hematocrit 3. rate of depolarization of action potential in SA node 4. blood flow to kidneys 5. blood flow to GI tract 6. blood flow to skin 7. frequency of action potentials in afferent nerves from baroreceptors to medulla 8. frequency of action potentials in sympathetic nerves to blood vessels in the muscles 9. heart rate http://mcb.berkeley.edu/courses/mcb136/topic/Muscle_Cardiovascular/0Problems/ MCB 136 Review | Muscle & Cardiovascular Review Answers | Skeletal, Cardiac and Smooth Muscle 1. T 2. sarcoplasmic reticulum, Ca 3. smooth, cardiac >> skeletal 4. the action potential 5. Defective titin might show as reduced passive tension properties of heart muscle cells and might lead to increased filling and over-stretching of the heart during diastole. 6. myosin 7. smooth, cardiac or skeletal 8. Twitch: one action potential, one release and then reuptake of Ca from SR, and one contraction. Summation: repeated action potentials at intermediate levels of stimulation, repeated release and uptake of Ca from SR, but because the reuptake does not have time to occur completely the next contraction occurs with higher [Ca] and is more vigorous than the first. Tetanus: repeated, rapid action potentials, repeated release of Ca; Ca-ATPase cannot keep up with the rates of release, so Ca remains in the cytosol and causes continual contraction, as long as energy supplies are maintained to allow myosin to continue cycling. The very long depolarization/repolarization cycle for cardiac cells prevents rapid successive contractions or excessive build-up of cytosolic [Ca]. 9. See notes and book for description of A and I bands and Z-lines; ATP in power stroke and release of actin; degrees of overlap of thick/thin filaments. 10. smooth, smooth 11. Number of motor units stimulated and degree of stimulation (summation). 12. Blocks the acetylcholine receptor in muscle membranes, preventing the synapse's chemical signal (acetylcholine) from being reconverted into an electrical one in the muscle membrane. However, the muscle remains functional and can therefore still contract when a muscle action potential is directly initiated with an electrode. 13. Presence of Ca and ATP: muscle would contract and perhaps get shorter. Absence of Ca and presence of ATP: relax 14. F. ATP must still be available during fatigue because rigor state has not been reached. Review Answers | Coordinated activities of heart and blood vessels 1. Because a significant amount of Ca enters cardiac cells across the plasma membrane, this treatment would reduce heart contraction. 2. Contractile force (ATPase activity of myosin), detaching actin from myosin, Ca pumping by PMCA and SERCA during relaxation. In addition, ATP is used for generating the ion gradients used for electrical activity of the heart. 3. Multiple effects are possible. Caffeine might lead to increased contractile strength initially because more Ca would be released. However, if SR remains "leaky" due to SR channel remaining open too long, possible that relaxation of heart is disrupted. Since caffeine is PDE inhibitor, there may be increased levels of cAMP, which would lead to effects noted above for epinephrine. It is perhaps understandable that one's heart can beat irregularly following too much coffee. 4. Epinephrine → increased cAMP → phosphorylate Ca entry channel → increased cytosolic Ca for contraction. Increased phosphorylation of phospholamban → more rapid pumping of Ca into SR → increased rate of relaxation and increased Ca pumping during following beat. 5. Action potential is prolonged due to presence of K channels that inactivate, and Ca channels that open, in response to initial peak of depolarization, resisting repolarization that would otherwise occur when fast Na channels close. Extended duration/plateau phase of the action potential is ended by a second type of K channel, opened very slowly by depolarization, and by slow closing of Ca channels. 6. b 7. d Coronary blood supply exhibits little branching, so blockage of one coronary artery or arteriole can have disastrous consequences for heart, which continually beats and therefore needs a continual supply of nutrients. If this supply is interrupted (e.g., by occlusion of coronary vessel with a blood clot or with athersclerotic plaque), heart muscle cells die, resulting in heart attack. Explanation for measurements of lactic dehydrogenase and troponin in blood is given in text (p. 461). 8. F. Correct sequence: SA node, atria, AV node, bundle of His, ventricles 9. Resting membrane potential depends on low [K]out vs high [K]in. Increased [K]out causes cell potential to depolarize towards zero, which opens K channels and inactivates Na channels, leading to a cell that cannot be excited and rapid stoppage of heartbeat. 10. Single unit smooth muscle has gap junctions, so all cells contract as a unit, as action potentials conduct from one cell to the next. 11. Smooth muscle can contract without ever exhibiting an action potential. Hormones can elicit contraction through activation of IP3 receptors, without activation of voltage-sensitive Ca channels in plasma membrane. 12. ACh causes heart to contract more slowly due to effects on SA node (slowing the gradual depolarization phase of the cardiac action potential), while norepinephrine increases contractile strength and rate (effects noted above). ACh causes smooth muscle to relax (dilate), while norepinephrine usually causes smooth muscle to contract. However, there are exceptions to this, depending on the specific adrenergic receptor present (beta 1 vs beta 2). 13. T. Vagus has tonic activity, which keeps SA node under constant inhibitory pressure. When vagus is cut, the inherent, uninhibited rhythm of SA node can be expressed and heart speeds up. 14. F. ESV is never 0 ml, but typically ~50 ml. 15. T. The left ventricle pumps slightly more blood than the right, because of cardiac and pulmonary "shunts" that return some deoxygenated blood directly to the left heart. Review Answers | Hemodynamics and Vessel Functions 1. 1. arterial blood pressure = blood flow × peripheral resistance. Since blood flow increases yet mean art. pressure did not change, peripheral resistance had to decrease. This is due to dilation of vessels leading to exercising muscles. 2. Blood flow to the GI tract decreased due to the increase in resistance with little change in mean arterial pressure. 2. a. ii, iii, vii; b. i, ii, iii; c. iii, v; d. ii, iii, iv, vi, viii; e. i, ii, iii, ix 3. 120, systolic; 80, diastolic 4. flow decreases by factor of 16 — see Poiseuille's law. 5. a, b 6. t = 200 msec, D = 10–5cm2/sec, Dx = radius = 20 um. Since muscle cells are often much larger than this, they have evolved the mechanisms to assure rapid spread of action potential deep into cells (T-tubules) and release of Ca from stores (SR) very close to the site of Ca function in the sarcomere. 7. See notes 8. See notes 9. See notes 10. 120 mm Hg × 1 cm H2O/0.74 mm Hg = 162 cm × 1 in/2.54 cm × 1 ft/12 in = 5.3 ft. 11. Pulse pressure = systolic - diastolic. Pulse pressure determined by stroke volume, arterial compliance and peripheral resistance. Arteriosclerosis leads to decreased compliance and results in increase in pulse pressure. 12. Usually use sphygmomanometer to measure blood pressure. Cuff around arm, decreasing blood flow to zero. Gently release pressure, as blood squirts through small opening of artery, turbulent flow gives rise to sound. The pressure at point when first sound is audible is systolic pressure. Pressure at last sound before flow returns to laminar (silent) is diastolic pressure. 13. Law of Laplace: DP = T (1/r1 + 1/r2). For bubble, DP = 2T/r; for cylinder DP = T/r. This law explains how capillaries can withstand high pressure. Law of Laplace also shows that a dilated or expanded heart will necessarily have to generate more tension to elicit same pressure as a more contracted heart. Thus, Law of Laplace and Starling's law tend to work against each other. In general, Starling's law is important for normal heart function, while debilitating effect of Law of Laplace comes into play at larger than normal heart volumes. 14. Pressures in the heart, aorta and large arteries are all about the same in a supine person due to fact that little of the energy of the heart has been dissipated in large arteries. When person stands, gravitational forces come into play, and transmural pressures at level of kidney would increase above, and those in head would decrease below, those in the heart. 15. Slope of this relationship for veins is the compliance, which is larger for veins than for arteries. Review Answers | Capillary exchange: diffusion and osmosis, lymphatics and edema 1. If filtration pressure and osmotic pressure are imbalanced, fluid will flow into or out of capillaries. In latter case, edema results. Protein deficiency causes reduction in colloid osmotic pressure, and reduced fluid flow back to capillaries, → edema. Lymphatics drain excess tissue fluid, approx 3 liters per day in systemic circulation. Pulmonary lymphatics are also important for maintaining dry airways for efficient O2 and CO2 exchange. 2. Pressure in the capillary bed increases. 3. a, b, g, h (affects area of the capillary available for diffusion to occur); rate of blood flow will be only indirectly important, e.g., if the rate is so slow that the oxygen concentration of the capillary drops to low levels because the oxygen in capillary is not being replenished. 4. a, b, e 5. Lymph vessels have valves, like the veins, and muscle pump aids in generating pressures required to move lymph along the lymph vessels. 6. a. glucose - diffusion b. oxygen - diffusion c. carbon dioxide - diffusion d. proteins - diffusion e. amino acids - diffusion f. lactic acid - diffusion g. water - osmosis, filtration (there is no net diffusion of water across the capillaries since concentrations of water are identical on the two sides of the capillary membranes) 7. Osmotic pressure of plasma is due to all dissolved solutes (Na, Cl, HCO3, glucose, amino acids, proteins etc). Colloid osmotic pressure is osmotic pressure due to presence of the plasma proteins only, and is much smaller than total osmotic pressure. Much smaller molecules do not influence water flow across the capillary wall because they are so permeant that they do not elicit any osmotic flow. Review Answers | Regulation of blood pressure and flow 1. Increased flow velocity indicates a vessel is too constricted. This can lead to production of nitric oxide in endothelial cells in the affected area. Nitric oxide in turn leads to relaxation of nearby smooth muscle, and dilation of the affected vessel. 2. Frank-Starling relationship showed that increased stretch of heart (EDV) caused increased stroke volume and increased systolic pressure. Since each heart has its own P-EDV relationship, moment-to-moment changes in venous return will be compensated automatically by the F-S mechanism. Despite these moment-to-moment changes, the left and right hearts pump nearly the same amounts at any given time, because the left heart's F-S mechanism adjusts to whatever blood flow is delivered from the pulmonary veins (determined almost entirely by the right heart's output). Sympathetic nerves change the relationship between P and EDV, moving to larger P (and therefore larger stroke volume) for any given EDV. Contractility is the inherent ability of the ventricles to generate tension based on actin-myosin interactions and the amount of Ca reaching the cytosol, both from the SR and through the plasma membrane. Elevation of cytosolic Ca can be increased by sympathetic stimulation. 3. Flow = CO = arterial pressure/(TPR). Increased stroke volume increases pulse pressure, and arterial compliance increase will decrease pulse pressure. 4. Arterioles receive sympathetic nerve innervation. Norepinephrine is transmitter. Blood vessels in brain and coronary circulation do not respond very prominently to sympathetic stimulation. Arterioles are often not innervated by parasympathetic fibers, but parasympathetic stimulation can lead to reduction in sympathetic constriction and, therefore, in increased blood flow. Alpha receptors lead to constriction. Skeletal muscle arterioles dilate during sympathetic stimulation. 5. Local control wins. 6. Baroreceptors are stretch receptors in the walls of the aortic arch and carotid sinus. They send action potentials (frequency codes pressure) to medulla oblongata (center), which processes information and then sends out sympathetic or parasympathetic impulses depending on whether pressure was too high or too low. 7. a. increased — many arterioles constrict, leading to increased total peripheral resistance b. decreased — ↓ BP → ↓ filtration; continued osmotic absorption → ↑ fluid in plasma; with no change in red cells, ↓ hct. c. increased — leading to increased rate of action potential generation d, e, and f. all decreased, due to constriction of arterioles and consequent reduction in blood flow g. reduced — baroreceptors respond to reduced pressure with fewer action potentials h. increased — response to baroreceptors i. increased — response to increased sympathetic output