CARDIOVASCULAR. Section 2

Transcription

1 CARDIOVASCULAR Section 2 1

2 I. General Aspects of the Cardiovascular System The Peripheral Circulation A. closed circuit with 2 pumps connected in series, therefore, pulmonary and systemic circuits are connected in series B. when systems are connected in series flow must be equal in the 2 circuits II. Structure-Function Relations A. Pressure largest drop is across the arterioles, smallest drop is in the major arteries pressure drop over a segment is directly related to the resistance of that segment B. Velocity - greatest in the aorta, decreases to a minimum in the capillaries and then increases from the venules to the right atrium C. Cross sectional area- inversely related to velocity, therefore greatest in the capillaries. Note: a segments cross sectional is not related to its resistance D. Blood volume - largest in the systemic veins which constitutes the major blood reservoir 2

3 DIRECTIONS: (Questions 1-3) Select the one best answer A. aorta B. large arteries C. arterioles D. capillaries E. veins 1. Slowest velocity of blood 2. Highest resistance to blood flow 3. Where the largest volume of blood is found III. Hemodynamics Flow Flow = P 1 - P 2 P 1 -- upstream pressure for segment or circuit P 2 -- pressure at the end of the segment or circuit R -- resistance of vessels between P 1 and P 2 Systemic circuit as a whole F = cardiac output P 1 = aortic pressure P 2 = pressure at the entrance to the right atrium R = resistance of all vessels in the systemic circuit (=total peripheral resistance TPR) If P 2 (right atrial pressure) approximated as zero, then: CO = MAP CO = cardiac output TPR MAP = mean arterial pressure or MAP = CO x TPR TPR = total peripheral resistance There are 2 types of flow: 1) laminar flow or flow in layers -silent -normal cardiovascular system excluding flow in the heart 2) turbulent flow -noisy, murmurs present The following will tend to promote turbulent flow (i.e. increase Reynold s number): 1) decreasing viscosity 2) increasing tube diameter 3) increasing velocity 3

4 B. Resistance With laminar flow resistance can be calculated for a vessel Rα nl n = viscosity r4 L = length r = radius The most important factor determining the resistance is the radius of the vessel. This is how resistance is varied in the arteriole which are the main regulators of flow distribution and make up the greatest component of the TPR. When resistance factors are included in our equation relating flow pressure and resistance we have what is referred to as the Poiseuille equation. Q = π (P 1 P 2 ) r 4 Q = flow 8 nl With turbulent flow resistance is always greater Resistance in series vs. resistance in parallel Series: R T = R 1 + R 2 =R 3 The total resistance is the sum of individual resistances. Therefore, the total is always greater than any of the individual resistances If Pin and Pout are kept constant, what happens to the following if the central resistance increases: A. flow through R 1, R 2 and R 3 B. P b C. P a 4

5 Parallel: 1/RT = 1/R 1 + 1/R 2 + 1/R 3 The reciprocal of the total resistance is the sum of the reciprocals of the individual resistances. Therefore the total is always less than any of the individual resistances R T =? R 1 = 400 ml/min of flow R T =? R 2 = 600 ml/min of flow If in the above example the input and output pressures are kept constant, what happens to flow through R 1 and R 2 if R 1 resistance increases: DIRECTIONS: Select the one best answer 1. Under which one of the following conditions is an increase in arterial pressure associated with a decrease in peripheral resistance? A. when there is turbulence B. when there is an increased Hematocrit C. when there is vasoconstriction D. when there is vasodilatation E. when there is an increased cardiac output 5

6 2. In the above diagram, the resistance to blood flow in the three organs arranged in parallel are indicated. Calculate the total resistance in these vascular beds. A. 9 B. 6/11 C. 11/6 D. 3 E The parameter that is most responsible for the change in resistance to blood flow in a healthy individual is the: A. length of the vessel B. viscosity C. radius of the arterioles D. radius of the aorta E. radius of the capillaries 4. The cardiac output of an individual with the following hemodynamic status would be (liters/min): Pulmonary arterial pressure = 24 mmhg Right atrial pressure = 2 mmhg Left atrial pressure = 4 mmhg Pulmonary vascular resistance = 2 mmhg/liter/min Systemic vascular resistance = 20 mmhg/liter/min HINT: Use values for pulmonary circuit A. 1.0 B. 1.1 C. 10 D. 11 E. cannot be determined from the above information 6

7 5. The below figure shows a recording of blood flowing through an organ at a constant perfusion pressure. At the arrow, the resistance to blood flow suddenly increases. Which tracing indicates the blood flow occurring after the increase in resistance? 6. Which of the following units would be correct for the measurement of resistance to flow? A. cm H 2 O B. cm H 2 O/liter/second C. cm H 2 O x liter x second D. ml/min/mmhg E. dimensionless (no units appropriate) 7. Calculate the total resistance of an individual from the following measured parameters: Mean arterial pressure = 100 mmhg Central venous pressure = 0 mmhg Cardiac output = 5 L/min In peripheral resistance units (mmhg/l/min) the total peripheral resistance of this individual is: A. 100 B. 50 C. 20 D. 5 E

8 DIRECTIONS: Choose the false statement 8. A. The vascular resistance of the lower extremities (or renal circulation) is lower than the resistance of the cutaneous vasculature of the left thumb. (or coronary circulation) B. In a normal individual the compliance of the aorta is greater than the femoral artery (measured at a pressure close to 100 mmhg) C. The blood volume of the systemic veins is approximately equal to the blood volume of the entire pulmonary circulation. D. Doubling the radius of a vessel will later alter resistance more than doubling the length of a vessel 9. A. The large pressure drop across the arterioles is related to the large resistance in these vessels B. Proceeding from the aorta peripherally to the arterioles resistance to flow will increase and total cross sectional area will decrease C. Adding a resistance in series will always increase the overall resistance in the system D. Adding a parallel circuit, to a given system will always decrease the resistance in the system DIRECTIONS: Select A if only 1, 2 and 3 are correct (Questions 10-14) B if only 1 and 3 are correct C if only 2 and 4 are correct D if only 4 is correct E if all are correct 10. A pattern of turbulent rather than laminar flow in a systemic artery: 1. is more likely to occur in the aorta than in the femoral artery 2. is more likely to occur when there is a redaction in blood viscosity, as in anemia 3. results in a higher pressure gradient for a given flow 4. is associated with flow in distinct layers 11. Characteristics of the systemic veins include: 1. sparse sympathetic innervation 2. a pressure of about 40 mmhg in the recumbent position 3. only a small volume of blood is present 4. high distensibility of the venous wall 12. The pressure gradient across a long tube with a flow of 5L of water/min/ (mmhg/l/min = PRU): 1. would be 10 mmhg if the resistance was 2 PRU 2. would be less if a parallel circuit of high resistance was added 3. would be lower if flow was lowered to 2 L/min 4. would increase if an 80% stenosis which raised resistance was added in the middle of the tube 8

9 13. Turbulent flow in an artery can be induced by: 1. a decrease in the density of blood (this is true, usually not tested) 2. an increase in velocity of blood 3. an increase in diameter of the blood vessel 4. a decrease in the velocity of the blood 14. In the diagram below, flow is constant, P = pressure and R = resistance. R 1 in region A = R 1 in region B, likewise R 2 in region A = R 2 in region B, R 3 in region A = R 3 in region B Which of the following statements is/are correct? 1. the total resistance of region A is the same as total resistance of region B 2. the pressure drop across R 1 (P 1 - P 2 ) in region A will equal the pressure drop across all of the region B (P 4 - P 5 ) 3. the pressure drop across region A (P 1 - P 4 ) will equal the pressure drop across region B (P 4 - P 5 ) 4. P 4 will be less than P 3 but greater than P 5 9

10 15. What would be the total resistance by the following three resistances in parallel with each other: resistance f: 0.2 PRU resistance g: 0.4 PRU resistance h: 0.2 PRU A. 0.8 PRU B. 0.4 PRU C. 0.3 PRU D. 0.2 PRU E PRU IV. Systemic circuit pressure - arterial: systolic, diastolic, mean - pulse pressure (systolic diastolic) - mean is average pressure and will be approximated by the following formula mean pressure = diastolic + 1/3 pulse pressure compliance - C = ΛV ΛP - arterial system - aorta most compliant artery, compliance decreases peripherally - pulse pressure related to compliance - aorta - smallest pulse pressure, pulse pressure increase peripherally and dissipated in arterioles Which pressure pulse represents the aorta and which represents the femoral artery? What is the effect of age on the pressure pulse? - veins are more compliant than arteries (in operating range) 10

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12 DIRECTIONS: Select the one best answer 1. In going from a lying down to an upright position the change in pressure will be greatest in which of the following vessels? A. aorta B. pulmonary artery C. femoral artery D. subclavian artery (large artery, shoulder area) E. pulmonary vein 2. The blood pressure of a person who is standing up is highest in the: A. femoral artery B. dorsalis pedis artery (an artery in the feet) C. radial artery (an artery in the arms) D. cerebral artery E. aorta 3. A 10-cm strip of artery with no branches was isolated and clamped centrally and peripherally. The pressure in the strip was 90 mmhg before and 120 mmhg after the injection of 3ml of blood. What was the compliance of this strip of artery? 4. A saccular aneurysm in the abdominal aorta is more likely to rupture than the part of the aorta that carries blood to it because: A. more tension is exerted on the wall of aneurysm B. there is less pressure in the aneurysm C. there is less turbulence in the aneurysm D. there is more tension exerted on and less turbulence in the aneurysm E. there is more pressure and less turbulence in the aneurysm 12

13 5. A 70-kg 6-foot, normal healthy subject standing quietly erect for 30 seconds has a mean arterial pressure of 100 mmhg in the ascending aorta and a venous pressure of 2 mmhg in the superior portion of the inferior vena cava. What is the pressure in the veins of the dorsum of the foot: A. less than 0 mmhg (i.e. below atmospheric pressure) B. 2 mmhg C. 4 mmhg D. about 20 mmhg E. above 40 mmhg 6. In the horizontal subject, the greatest pressure head ( i.e., P1 - P2) exists between: A. the ascending aorta and the anterior tibial artery B. the anterior tibial artery and the anterior tibial vein C. the anterior tibial vein and the right atrium D. the pulmonary artery and the pulmonary vein E. the efferent renal arteriole and the renal vein V. The Microcirculation A. General Characteristics Flow and pressure within the system controlled by varying the radius (resistance) of the arterioles Capillaries are the major exchange vessels and tissue density of capillaries related to tissue flow requirements- high density tissues brain, heart moderate density skeletal muscle low density bone, connective tissue Capillaries generally permeable to all dissolved substances (except plasma proteins which leak out slowly into the interstitial fluid) most permeable liver least permeable brain 13

14 B. Capillary Exchange a) diffusion process involved in the exchange of nutrients and gases between blood and tissue b) filtration and reabsorption of fluid due to osmotic and hydrostatic pressures in the capillary and interstitium normal situation filtration at the arterial end and reabsorption at the venous end -- excess fluid returned via lymphatics C. edema promoted by: 1) increased capillary hydrostatic pressure 2) increased interstitial osmotic pressure (leakage of plasma proteins) 3) decreased plasma osmotic (oncotic) pressure due to decrease concentration of plasma protein 4) lymphatic blockage DIRECTIONS: Select the one best answer In the following example, determine the filtration or reabsorption pressures in a capillary subjected to the following conditions: capillary hydrostatic pressure at the arterial end = 30 mmhg plasma oncotic (colloidal) pressure = 23 mmhg tissue hydrostatic pressure = 1 mmhg tissue oncotic pressure = 0 mmhg capillary hydrostatic pressure at the venous end = 10 mmhg 1. The capillary filtration pressure at the arterial end in mmhg is: A. 2 B. 4 C. 6 D. 8 14

15 2. The capillary reabsorption pressure at the venous end in mmhg is: A. 7 B. 12 C. 14 D If the hydrostatic pressure in the capillary is 10 mmhg, interstitial pressure is 2 mmhg, colloid osmotic pressure of blood 24 mmhg and interstitial fluid osmotic pressure is 5 mmhg, which of the following is correct for this situation? A. filtration with a net pressure of 18 mmhg B. filtration with a net pressure of 12 mmhg C. reabsorption with a net pressure of 18 mmhg D. reabsorption with a net pressure of 12 mmhg 4. Net movement of fluid from the intravascular space to the interstitial space occurs with all the following conditions EXCEPT: A. constriction of postcapillary venules B. decreased plasma albumin concentration C. lymphatic obstruction D. constriction of precapillary arterioles E. activation of bradykinin 5. If the osmotic pressure of the blood is 25 mmhg and the interstitial fluid is 5 mmhg and the hydrostatic pressures in the capillary and interstitial space are 20 and 0 mmhg respectively, which of the following statements are true? A. there is a net movement of fluid from the capillary to the interstitial space with a net pressure of 10 mmhg B. there is a net movement of fluid from the capillary to the interstitial space with a net pressure of 5 mmhg C. there is a net movement of fluid from the interstitial space to the capillary with a net pressure of 10 mmhg D. there is a net movement of fluid from the interstitial space to the capillary with a net pressure of 5 mmhg E. filtration and reabsorption factors are balanced and no net movement of fluid acres the capillary is occurring 15

16 DIRECTIONS: Select A if only 1, 2 and 3 are correct (Questions 6 10 B if only 1 and 3 are correct C if only 2 and 4 are correct D if only 4 is correct E if all are correct 6. Edema formation can occur from: 1. an increase in interstitial fluid pressure 2. an increase in venous pressure 3. a decrease in capillary filtration 4. a decrease in plasma oncotic pressure 7. Lymph capillaries differ from systemic blood capillaries in that they: 1. are less permeable 2. are not lined by endothelium 3. lack valves 4. are absent in the central nervous system 8. Which of the following can cause edema? 1. decreased plasma concentration of albumin 2. increased venous pressure 3. damage to capillary endothelium 4. blockage of lymph ducts 9. Cardiovascular disturbances that lead to tissue edema include: 1. venous obstruction 2. low intravascular protein concentration 3. lymphatic obstruction 4. arteriolar vasoconstriction 10. True statements concerning fluid exchange across the microvascular bed include which of the following: 1. fluid exchange follows the laws of pressure filtration across a semipermeable membrane 2. fluid is filtered outward at the arterial end of the vascular bed 3. edema occurs if the plasma protein concentration is reduced drastically 4. edema occurs if the arterial blood pressure decreases 16

17 VI. Regulation of Blood Flow at the Organ Level A. Autoregulation (control mechanism within the organ itself) note what is regulated is blood flow -- no nerves involved -- no circulating hormones involved Metabolic hypothesis tissue produces a vasodilatory metabolite Major characteristics of an autoregulating tissue -- blood flow independent of blood pressure -- blood flow proportional to tissue metabolism -- blood flow independent of nervous reflexes (e.g. carotid sinus) Autoregulating tissues include: (least affected by nervous reflexes) -- cerebral circulation -- coronary circulation -- skeletal muscle vasculature during exercise B. Nervous and humoral factors originating outside the organ e.g. resting skeletal muscle + constricts - dilates sympathetic adrenergic sympathetic cholinergic no significant effects of parasympathetics Circulation with mainly extrinsic regulation most affected by nervous reflexes cutaneous circulation resting skeletal muscle C. Control of resting vs. exercising muscle - rest flow altered mainly by increasing or decreasing sympathetic adrenergic activity - anticipation of exercise flow increases by: 17

18 a) B2 activation by increases in circulating epinephrine b) activation of sympathetic cholinergics - exercising muscle control mainly via vasodilatory metabolites DIRECTIONS: Select the one best answer 1. Which one of the following represents a vasodilatory autoregulatory response? A. a decrease in sympathetic tone in skeletal muscle blood vessels B. activation of skeletal muscle B 2 receptors by a circulating agonist C. activation of sympathetic cholinergic fibers D. none of the above 2. Peripheral vascular resistance is mediated primarily by the smooth muscle tone of peripheral arterioles. Increased peripheral vascular resistance will be produced by: 1. discharge of sympathetic cholinergic fibers 2. histamine 3. adenosine 4. norepinephrine VII. Special Circulations A. Coronary circulation 1. coronary blood flow patterns Right and left coronary arterial flow during systole and diastole. Note the greater effect of external compression on systolic flow to the left coronary as compared to the right. (Reprinted with permission from B. Falkow and E. Neil, Circulation, London: Oxford University Press, 1971) 2. characteristics of left-coronary blood flow a) most of the blood flow is during diastole* b) a slight reversal of flow may be seen at the beginning of systole c) blood flow during systole and diastole oscillates with arterial blood pressure 3. characteristics of right coronary blood flow a) no reversal of blood flow during the cardiac cycle b) compared to the left ventricle, blood flow to the right ventricle during systole comprises a much greater proportion of total coronary blood flow** **coronary venous PO 2 is the lowest in the systemic circuit in a resting individual 18

19 4. regulation of coronary blood flow coronary blood flow directly proportional to myocardial metabolism. The following will increase coronary blood flow because they also increase the demands of ventricular pumping -- exercise -- increased heart rate -- increased arterial pressure (hypertension) -- increased contractility Likewise the following decrease coronary blood flow -- hypotension -- decreased heart rate -- decreased contractility -- flow not affected by baroreceptor reflexes unless heart metabolism changes. B. Cerebral Circulation -- flow proportional to arterial PCO2 -- (large) decreased in PO2 of the arterial blood will increase blood flow -- baroreceptor reflexes do not affect flow C. Cutaneous Circulation -- almost entirely controlled via sympathetic adrenergic nerves -- large venous plexus innervated via sympathetics -- A-V shunt innervated by sympathetics -- sympathetic stimulation causes: 1. constriction of arterioles and a decrease in blood flow 2. constriction of the venous plexus and a decrease in blood volume 3. increase in velocity of blood -- sympathetic activity varies with the body s need for heat exchange with the environment D. Pulmonary Circuit --low pressure -- blood flow not regulated -- low resistance -- blood volume and blood flow -- passive -- very compliant EXERCISE large in C.O. pulmonary volume dilation of vessel due to passive compliant nature of circuit large in resistance. --only slight increase in pressure 19

20 DIRECTIONS: Select A if only 1, 2 and 3 are correct (Questions 1-4) B if only 1 and 3 are correct C if only 2 and 4 are correct D if only 4 is correct E if all are correct 1. Local control of the circulation predominates over neutral control in which of the following organs? 1. brain 2. skin 3. exercising skeletal muscle 4. liver 2. During vigorous exercise, skeletal muscle blood flow increases tremendously. Circulatory adjustments responsible for this change include: 1. increased B-adrenergic receptor stimulation in skeletal muscle blood vessels 2. local vasodilatation in skeletal muscle 3. increased cardiac output 4. increased cardiac parasympathetic stimulation 3. Which of the following represent exercising as opposed to resting skeletal muscle: 1. a lower lymph flow 2. a lower arterio-venous oxygen difference 3. a lower capillary hydrostatic pressure 4. a lower vascular resistance 4. Features of the pulmonary circulation include: 1. operation in parallel with the systemic circuit 2. pressure is lower but resistance is higher than in the systemic circuit 3. contains over 80% of the individuals blood volume 4. the ratio of flow in the pulmonary artery to flow in the aorta is normally

21 DIRECTIONS: Select the one best answer 5. Which of the following is least likely to influence cerebral blood flow? A. PO 2 of the arterial blood B. cerebrospinal fluid pressure C. ph of the interstitial fluid of the brain D. PCO 2 of the arterial blood E. vasomotor reflexes 6. Which of the following variables is most similar in the pulmonary circulation and the systemic circulation: A. mean arterial pressure B. resistance to flow C. capillary pressure D. blood flow E. diastolic arterial pressure 7. The cause of the increased blood flow to skeletal muscles during exercise is: A. adrenal release of epinephrine B. increased resistance to flow in other muscles C. stimulation of cholinergic vasodilator nerves D. increased cardiac output E. local production of vasodilatory metabolites 8. A hypothetical drug given intravenously caused a decrease in mean arterial pressure and a the same time a decrease in the heart rate. Which of the following could explain the action of this drug? A. stimulation of B1 and B2 receptors B. stimulation of α receptors C. blocking of parasympathetic effects in the heart muscle D. activating histaminergic receptors E. increases in the firing rate of the baroreceptor nerves DIRECTIONS: True or false (Questions 9-10) 9. An injection (IV) of epinephrine which increases systemic arterial pressure and heart rate will also result in an increase in coronary blood flow. 10. The ratio of diastolic coronary blood flow to systolic coronary blood flow is greater for the left than for the right coronary artery. 21

22 Questions Select all the correct answers 11. In the heart, brain, skeletal muscle, liver, kidney and intestine, 1 minute of vascular occlusion is followed by which of the following changes when the occlusion is removed. HINT: this is reactive hyperemia (check the two correct answers)? 1. a period of 15 to 30 seconds during which flow progressively increases to the preocclusion value 2. a rapid (less than 2 seconds) return to the preocclusion flow 3. a period of 15 seconds or more during which the flow is markedly higher than it was prior to occlusion 4. a change in flow produced primarily by adrenergic sympathetic neurons 5. a change in flow produced primarily by cholinergic sympathetic neurons 6. a change in flow produced primarily by the accumulation of vasodilator metabolites 7. a change in flow produced primarily by local heating of the tissue 12. The pulmonary circulation differs from the systemic circulation in that in the pulmonary circulation (check each correct statement): 1. the veins do not contain an important reservoir of blood for the heart 2. the arterial system is more distensible 3. adrenergic sympathetic neurons are less important in controlling arteriolar and precapillary resistances 4. the capillaries have a higher transmural pressure 5. the arteries serve as more important blood reservoirs 6. obstruction of blood flow is much more likely to cause a retrograde ventricular failure 13. Systemic arterial pressure in the adult is approximately six times that of pulmonary arterial pressure because (select the one best statement): A. left ventricular stroke volume is greater than right ventricular stroke volume B. systemic blood volume exceeds pulmonary blood volume C. systemic resistance exceeds pulmonary resistance D. pulmonary compliance exceeds systemic compliance E. intraabdominal pressure exceeds intrathoracic pressure 14. During early ventricular systole, coronary blood flow: A. is more likely reduced at the subepicardial surface than the subendocardial surface B. is markedly reduced because the cusps of the aortic valve occlude the coronary arteries and therefore protect them from excess pressure C. in the left coronary artery goes to near O or below D. in the right coronary artery goes to near O or below E. is well characterized by all of the above statements 15. Which one of the following structures in the resting subject receives the greatest blood flow per gram of tissue? A. brain B. heart C. liver D. gastrocnemius muscle E. kidney 22

23 VIII. Basic Alterations during Exercise A. Pulmonary circuit - blood flow (cardiac output) large increase - pulmonary arterial pressure - pulmonary vascular resistance - pulmonary blood volume - number of perfused capillaries - capillary surface area note: -- the pulmonary circuit is a very compliant non-regulated circuit B. Systemic circuit arterial system PO 2 PCO 2 ph pressure flow resistance (TPR) venous system PO 2 PCO 2 C. Regional circulating 1. skeletal muscle anticipation of exercise 2. skeletal muscle during exercise - blood flow - resistance - capillary pressure - filtration - lymph flow - venous PO 2 - extraction O 2 3. cutaneous circulation 4. coronary circulation 5. cerebral circulation 6. renal and GI circulation D. Heart (Innervated and denervated) 1. heart rate 2. stroke volume 23

24 IX. Arterial-venous Differences A. determined by 2 factors 1. blood flow 2. tissue metabolism B. arterial-venous difference 1. = + if substance extracted by the organ = - if substance produced by the organ 2. extracted substances = PO 2. glucose in skeletal muscle, lactate in heart muscle 3. produced substances = glucose in liver, lactate in skeletal muscle and ischemic muscle, PCO 2 C. points to remember: 1. in skeletal muscle the AV difference in O 2 increases during exercise since O 2 increases 2. the systemic arterial-mixed venous O 2 difference increases during exercise 3. coronary PO 2 AV difference is the greatest of all circulations in a resting individual 4. cutaneous PO 2 AV difference is small and becomes smaller when there is increased heat exchange with the environment Questions: 1. With exercise which increases more in skeletal muscle, flow or metabolism: 2. What does a vasodilatory drug (does not affect metabolism) do to AV differences of oxygen and dioxide? 3. Which of the following arterio-venous differences will be the greatest (in mmhg)? A. systemic arterial PCO 2 coronary venous PCO 2 B. systemic arterial PO 2 coronary venous PO 2 C. pulmonary arterial PCO 2 pulmonary venous PCO 2 D. pulmonary arterial PO 2 pulmonary venous PO 2 4. Between which of the following pair of vessels would the pressure difference be the greatest? A. aorta and femoral artery B. vena cava and right atrium C. femoral artery and capillary (in leg) D. pulmonary artery and pulmonary vein E. capillary and vena cava 24

25 The Heart I. Electrical Activity of the Heart A. Resting membrane potential of ventricular muscle Ion conc. out conc. in equil. pot. permeability Na low K high Ca low B. Action potential characteristics (fast response) 1. phases Changes in the conductances of Na+ (g Na ), Ca++ (g Ca ), and K+ (g k ) during the various phases of the action potential of a fast-response cardiac cell. The conductance diagram shows directional changes only. 2. ionic basis of the action potential - phase O gna (fast channels open), sodium influx - phase 1 - phase 2 gca (slow channels open), calcium influx gk, slowed K efflux - phase 3 gca gk, K efflux Which phase has: greatest gna greatest gca lowest gk 25

26 C. Action potential characteristics of nodal cells (SA node) 1. pacemaker potential (prepotential) - not propagated - effect of sympathetics; increase in slope - effect of parasympathetics; hyperpolarize without increasing the slope; - via increasing potassium conductance D. Conduction pathways and velocity of conduction E. Automaticity 1. SA nodal cells 2. AV nodal cells 3. purkinje cells F. Electrical event vs. mechanical event - refractory period 26

27 DIRECTIONS: Select all the correct answers. Questions Which of the following structures are commonly seen in both skeletal and cardiac muscle? 1. gap junctions 2. sarcoplasmic reticulum 3. somatic innervation (neuromuscular junction) 4. troponin 2. Which of the following changes would be expected to make the membrane potential of a muscle cell more positive than normal (resting) cell: 1. increased conductance to calcium 2. increased conductance to potassium 3. decreased conductance to potassium 4. decreased conductance to sodium DIRECTIONS: Select the one best answer. Questions 3 4 Correlate the ionic mechanism to the appropriate phases (labeled A-E) of an arterial action potential (Questions 5-6) 3. high Na + conductance 4. high Ca ++ conductance A. cardiac muscle B. skeletal muscle C. both D. neither 5. Force of contraction relatively insensitive to extracellular (Ca++) 6. Developed tension increases with increased free intracellular (Ca++) 27

28 II. Pumping Action of the Heart A. Systolic performance 1. preload load on the ventricle at the end of diastole a) indices of preload - left ventricular end diastole volume (LVEDV) - left ventricular end diastolic pressure (LVEDP) b) Less reliable indices of preload - atrial pressure - venous pressure 2. afterload load on the ventricle during systole a) indices - mean (aortic) pressure - peak left ventricular pressure 28

29 3. variations in systolic performance systolic performance Index of preload a) variations in preload - Frank-Starling mechanism b) variations in contractility (inotropic state) - a change in performance at a given preload c) mechanisms of action Frank-Starling the effect preload on sarcomere length - contractility due to changes in intracellular Ca ++ 29

30 4. Indices of contractility - dp/dt - aortic flow - ejection fraction Major effects of increased contractility 1. increased dp/dt 2. increased peak left ventricular pressure 3. increased rate of relaxation 4. decreased systolic interval 5. increased diastolic interval Effects of increased sympathetic activity on systolic and diastolic interval 1. systolic interval decreased contractility effect 2. diastolic interval decreased heart rate effect 30

31 B. Cardiac Function Curves 1. x axis LVEDV, LVEDP, atrial pressure, venous pressure 2. y axis ventricular performance e.g., stroke work, stroke volume, cardiac output 31

32 Left atrial, and left ventricular pressure pulses correlated in time with aortic flow, ventricular volume, heart sounds, venous pulse, and the electrocardiogram for a complete cardiac cycle in the dog 32

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34 D. Pressure volume Loops Pressure-volume loop of the left ventricle for a single cardiac cycle (ABCDEF) Major Features - point A opening of mitral valve A C ventricular filling - point C closing of mitral valve C D isovolumic contraction - point D opening of aortic valve D F ejection - point F aortic valve closes F A isovolumic relaxation Mechanical altered states : 1. aortic insufficiency 2. heart failure (decreased contractility) 3. aortic stenosis 4. increased contractility 34

35 E. Measurement of Cardiac Output 1. Fick principle Schema illustrates the Fick principle for measuring cardiac output. The change in intensity from pulmonary artery to pulmonary vein represents the change in color of the blood as venous blood becomes fully oxygenated - measurement - other uses e.g., O 2 consumption of organs 35

36 DIRECTIONS: Select the one best answer (Questions 1-2) The diagram above depicts four pressure-volume loops of the left ventricle (labeled A-D), illustrating different functional states. Loop D illustrates the control state. 1. Which pressure-volume loop best describes the response to a sudden increase in the afterload? 2. Which pressure-volume loop best describes the response to a negative inotropic agent? 36

37 (Questions 3 6) The following data were obtained from an individual: temperature = 980F pulse rate = 99 beats/min respiration = 12/min mean arterial blood pressure = 85 mmhg right atrial pressure = 1 mmhg oxygen consumption = 1372 ml/14 min pulmonary artery oxygen content = 14ml/100ml blood aortic oxygen content = 21 ml/100ml blood coronary sinus blood oxygen content = 5ml/100 ml blood end diastolic volume = 27 ml end systolic = 13 ml body surface area -= 0.47 m2 3. The cardiac output of this person is: CO = use Fick principle or CO = HR X SV A. 0.5L/min B. 1.0 L/min C. 1.4 L/min D. 14 L/min E. 28 L/min 4. The cardiac index of this person is: CI = CO/body surface area A. 1.0 L/min/m2 B. 1.5L/min/m2 C. 2.0 L/min/m2 D. 2.5 L/min/m2 E. 3.0 L/min/m2 5. The ejection fraction of this person is: EF = stroke volume/end diastolic volume A B C D E The total peripheral resistance of the systemic circulation of this person is: A. 20 resistance units (RU) B. 40 RU C. 60RU D. 80 RU E. 100 RU 37

38 The diagram above depicts four loops (labeled A-D) illustrating pressure-volume relationships of a left ventricle in different functional states. D = normal loop 7. Which P-V loop best describes the condition of aortic insufficiency? A. loop A B. loop B C. loop C D. loop D 8. Which of the four parts, labeled 1-4, in loop A coincides with the opening of the mitral valve? A. point 1 B. point 2 C. point 3 D. point 4 38

39 (Question 9) The following data were collected from an individual in a supine position: temperature = 98 0 F pulse rate = 83 beats/min respiration = 15/min blood pressure = 125/75 mmhg oxygen consumption = 1200 ml/12 min pulmonary artery oxygen content = 16 ml/100ml blood aortic oxygen content = 20 ml/100ml blood coronary blood flow to left ventricle = 100 ml/mon coronary sinus blood oxygen content = 5ml/100 ml blood body surface area = 8.3 m 2 9. the stroke volume of this individual is closest to: A. 30 ml B. 60 ml C. 70 ml D. 80 ml E. 90 ml 10. In aortic stenosis: A. the peak left intraventricular pressure is lower than systolic arterial blood pressure B. the peak intraventricular pressure is equal to the systolic arterial blood pressure C. the peak left intraventricular pressure is usually higher than the systolic arterial blood pressure D. both the peak left intraventricular pressure and systolic arterial blood pressure are higher than normal (ex. 120 mmhg) E. both the peak left intraventricular pressure and systolic arterial blood pressure are lower than normal 11. In mitral stenosis: A. both the left atrial pressure and the left ventricular pressure are higher than normal B. the left atrial pressure is higher than normal whereas the left ventricular pressure is equal to or less than normal C. the left atrial pressure is normal and the left ventricular pressure is higher than normal D. both the left atrial pressure and left ventricular pressure are lower than normal 39

40 Questions Select all the correct answers. 12. Which of the following changes in the ventricles can be due to the effect of epinephrine? 1. increased dp/dt of the intraventricular pressure 2. increased peak intraventricular pressure 3. increased rate of relaxation of the myocardium 4. increased rate of firing of the Punkinje fibers 13. The production of a second heart sound is due to the closure of the: 1. mitral valve 2. aortic valve 3. tricuspid valve 4. pulmonic valve 14. The dicrotic notch of the aortic blood pressure curve: 1. is produced by the contraction of the left ventricle 2. signals the beginning of the isovolumetric relaxation phase 3. associates with the third heart sound 4. signals the closure of the aortic valve 15. Increased volume work of the left ventricle occurs in: 1. aortic stenosis 2. anemia 3. interatrial septal defect 4. hyperthyroidism 16. Which of the following changes in cardiac function can be related to the effect of norepinephrine? 1. increased contractility 2. increased rate of phase-4 depolarization of the sinoatrial node 3. increased intraventricular pressure 4. increased force of contraction associated with increased end diastolic volume 40

41 III. The Baroreceptor Reflex and the Control of Blood Pressure 1. BP 2. BP Condition Afferent Act. Para. Sym. BP HR 3. Carotid Occlusion 4. Carotid Massage 5. Cut Afferents 6. Lying to stand Fluid Loss Orthostatic Hypotension 7. Volume Load 41

42 Questions 1-2. Select all the correct answers 1. A patient suffers a blood loss over a period of 20 minutes. At the end of this period, his arterial pressure has changed from 100 to 70 mmhg and his heart rate from 70 to 140/min. His hematocrit is 30% and his skin is cold. What other changes have occurred (check correct statement)? 1. a decreased capillary hydrostatic pressure 2. a decreased interstitial fluid volume 3. an increased plasma colloid osmotic pressure 4. an increased total systemic resistance 2. Some other responses to the hemorrhage discussed in question 1 include (check each correct answer): 1. a decreased glomerular filtration rate 2. a decrease in venous tone 3. sodium retention 4. a decreased secretion of antidiuretic hormone (ADH) 5. an increased production of angiotensin II (A-II) 3. The following record demonstrates an individual s response to acetylcholine (ACh): On the basis of these data and your understanding of physiology, what would you conclude? Acetylcholine produced: A. an increased pulse pressure B. an increased peripheral resistance C. a decreased arterial pressure due to venous dilation D. an increased systolic pressure E. a reflex increase in heart rate 42

43 4. You are given three catecholamine solutions of known concentration: norepinephrine, epinephrine, and isoproterenol. Each solution is injected separately into a conscious subject at a concentration of 2µg/kg of body weight. You can assume that, at this dose, isoproterenol stimulates only beta adrenergic receptors. What response would you obtain from the norepinephrine injection? A. a decrease in heart rate and an increase in arterial pressure that is more marked than those obtained from the other solutions. B. a decrease in peripheral resistance and heart rate that are more marked than those obtained with any of the other solutions C. a decrease in peripheral resistance and an increase in cardiac output that is more marked than with any of the other solutions D. an increase in skeletal muscle blood flow and a decrease in cutaneous blood flow 5. In question 4, which of the statements represents the response of an individual to epinephrine? 6. In question 4, which of the statements represents the response of a conscious individual to isoproterenol? 7. check each of the following changes produced by a decrease in the carotid sinus from 90 mmhg to 70 mmhg: 1. a decrease in the frequency of impulses moving centrally in the glossopharyngeal nerve 2. a reflex stimulation of cardiac sympathetic neurons 3. a reflex stimulation of cholinergic postganglionic sympathetic neurons Which one of the following best summarizes your conclusions? A. statement 1 is correct B. statement 2 is correct C. statements 1 and 2 are correct D. statements 2 and 3 are correct E. statements 1, 2 and 3 are correct Question 8. Select all the correct answers. 8. The total systemic peripheral resistance is increased in response to (check each correct statement ): 1. a decreased blood volume (i.e., hemorrhage) 2. changing from a reclining to a standing position 3. hypertension 4. lifting a heavy load 5. strenuous running 43

44 DIRECTIONS: Choose the answer that reflects a major change occurring with each of the following situations (Questions 9 12) A. increased left ventricular stroke volume B. increased right ventricular stroke volume C. decreased left ventricular stroke volume D. decreased right ventricular stroke volume E. A and B are correct 9. Aortic insufficiency 10. The beat that follows a sudden increased pulmonary arterial pressure 11. Patent ductus arteriosus 12. During exercise DIRECTIONS: Choose A if the following statement is true or B if it is false. (Questions 13-14) 13. The peak systolic wall tension of the left ventricle increases when the arterial blood pressure suddenly increases 14. The function of a baroreceptor reflex is such that an increased arterial blood pressure leads to decreased vagal parasympathetic activity 15. Aortic insufficiency A. increases aortic pulse and diastolic pressure B. increases pulse pressure and decreases diastolic pressure C. decreases aortic pulse and diastolic pressure D. is similar to vasoconstriction in that it decreases pulse pressure and increases diastolic pressure E. is similar to vasodilation in that it decreases pulse and increases diastolic pressure 16. Venous return to the right heart is normally increased by: A. increased minute ventilation B. increased venous tone C. increased cardiac sympathetic tone D. all of the above E. none of the above 44

45 17. Write in Column I each of the appropriate matches from Column II (f, g, h, etc.) Each item in Column II can be used once or more than once. The numbers in parentheses represent the number of appropriate matches for the items in Column I. Column I (Mechanism) 1. warming the blood to the hypothalamus of the brain causes a reflex vasodilation in this circulation (1) 2. a 30% decrease in the total blood volume does NOT cause a reflex vasoconstriction in this part of the systemic circulation (2) 3. resistance to flow increases in response to a local decrease in PO2 (1) 4. resistance to flow decreases during running even when body temperature remains constant (3) 5. contains high and low pressure capillaries that are in series with each other (1) 6. contains only low pressure capillaries (1) 7. its veins have the lowest concentration of oxygen found in the body (1) 8. its veins have the highest concentration of oxygen found in the systemic circulation (1) Column II (Systems) f. cerebral circulation g. coronary circulation h. cutaneous circulation i. gastrocnemuius muscle j. renal circulation k. pulmonary circulation 18. The following records were obtained from a patient with a decentralized heart (i.e., an individual who has received a heart transplant). In each of these records the aortic pressure was recorded at a constant paper speed and amplification Identify in questions 1 through 5 in which record (A through E) each of the indicated changes occurred. The arrow points to where the change began. 1. an increased left ventricular stroke volume 2. an increased heart rate 3. an increased total systemic resistance 4. aortic stenosis 5. aortic insufficiency 45

46 19. In a healthy individual two substances, f and g, are found to have a lower concentration on the venular side of a capillary than the arteriolar side. Their concentration in the blood changes as they pass through the capillary in the following manner. Concentration in the blood What valid conclusions can you make from this figure? A. substance f is blood flow limited (i.e., perfusion limited) B. substance g is diffusion limited C. both A and B are correct D. substance g could be O 2 E. all of the above are correct Exercise questions 1. Which one of the following is most likely to occur in a healthy subject in response to running? A. an increased coronary flow due to decreased cardiac adrenergic tone B. a generalized increase in blood flow (i.e., in the kidneys, muscle, stomach, etc.) due to an increased cardiac output C. both A and B occur during exercise D. a decreased velocity of flow in the capillaries of the lungs E. a decreased cardiac parasympathetic tone Question 2. Select all the correct answers. 2. During strenuous running, the cardiac output of a subject increased fourfold, the systemic a-v a2 difference changed from 4 to 12 volumes percent, and the mean pulmonary arterial pressure changes from 15 mmhg to 18 mmhg. Check each of the conclusions that can be drawn from this typical response to exercise. 1. the increased pressure was caused by an increased pulmonary resistance to flow 2. the pulmonary artery blood had a lower PO2 during exercise 3. changes in the pulmonary artery blood PO2 are, for the most part, responsible for the changes in the pulmonary peripheral resistance 4. none of the above are true 46

47 3. Which of the following is most likely to occur in a healthy subject in response to strenuous running? A. a decrease in the ejection fraction of the ventricles B. a decrease in the maximum dp/dt of the left ventricle C. an increase in circulation time D. a decrease in arteriovenous O 2 difference E. an increase in concentration of arterial lactate 4. In a healthy subject, running is usually associated with a decrease in the end-systolic volume of the right and left ventricles and with an increase in their stroke volume. The mechanism for this response is probably the following: A. Starling s law of the heart B. an increase in sympathetic tome to the ventricles C. an increase in parasympathetic tone to the ventricle D. a decrease in venous return of blood to the heart E. an increase in pulmonary and systemic resistance 5. Which of the following is not an important mechanism for increasing the blood flow at active skeletal muscle during exercise? A. an increased cardiac output B. an increased concentration of epinephrine in the vicinity of the blood vessels of active skeletal muscle C. an increased concentration of norepinephrine in the vicinity of the blood vessels of active skeletal muscle D. an increased concentration of Acetylcholine in the vicinity of the blood vessels of active skeletal muscle E. the action of metabolites on skeletal muscle blood vessels Question 6. Select all the correct answers. 6. A patient with a heart transplant is found to have no reinnervation of his heart. Check each of the following responses you expect him to have to moderate running and indicate the mechanism for each. 1. an increased venous return of blood to the heart 2. an increased heart rate that is more marked than that found in a normal subject during the same exercise 3. an increased stroke volume that is more marked than that found in a normal subject during the same exercise 4. a decreased sensitivity of the heart to circulating catecholamines 5. an increased stimulation of adrenergic sympathetic neurons to skeletal to muscle blood vessels 47

48 Answers to Cardiovascular Questions PAGE 2 1. D 2. C 3. E PAGES E 2. B 3. C 4. C 5. C 6. B 7. C 8. C 9. B 10. 1,2, ONLY 12. ALL 13. ALL ONLY 15. E PAGES C 2. B ml/mmhs 4. A 5. E 6. B PAGES C 2. C 3. D 4. D 5. E 6. 2 & ONLY 8. ALL 9. 1,2, ,2,3 PAGE D 2. 4 ONLY PAGES & ,2, ONLY 4. 4 ONLY 5. E 6. D 7. E 8. E 9. T 10. T & ,3,5 13. C 14. C 15. E PAGE metabolism 2. decrease 3. B 4. C PAGE & & 3 3. A 4. C 5. B 6. C PAGES A 2. C 3. C 4. E 5. C 6. C 7. B 8. B 9. A 10. C 11. B 12. ALL & & & ,2,3 PAGES ,2,4 2. 1,3,5 3. E 4. B 5. E 6. D 7. C 8. 1,2,4 9. A 10. D 11. A 12. E 13. A 14. B 15. B 16. D 17. 1) h 2) fg 3) k 4) gik 5) j 6) k 7) g 8) j 18. 1)D 2)C 3)A 4)B 5)E 19. D Exercise Pages E E 4. B 5. C 6. 1 & 3 48