Physiology Block 2 Cardiovascular
(D) Decrease to 1⁄16 If the radius of the artery decreased by 50% (1/2), then resistance would increase by 24, or 16 (R = 8ηl/πr4). Because blood flow is inversely proportional to resistance (Q = ΔP/R), flow will decrease to 1/16 of the original value.
1. A 53-year-old woman is found, by arteriography, to have 50% narrowing of her left renal artery. What is the expected change in blood flow through the stenotic artery? (A) Decrease to 1⁄2 (B) Decrease to 1⁄4 (C) Decrease to 1⁄8 (D) Decrease to 1⁄16 (E) No change
(C) 3 Closure of the aortic valve occurs once ejection of blood from the ventricle has occurred and the left ventricular pressure has decreased to less than the aortic pressure.
10. The aortic valve closes at point (A) 1 (B) 2 (C) 3 (D) 4
E) Excess extracellular fluid calcium ions The heart goes into spastic contraction following a large increase in the calcium ion concentration surrounding the cardiac myofibrils, and this occurs if extracellular fluid calcium ion concentration increases too much. An excess potassium concentration in the extracellular fluids causes the heart to become dilated because of the more positive resting membrane potential of the cardiac muscle fibers.
10. Which of the following is most likely to cause the heart to go into spastic contraction? A) Increased body temperature B) Increased sympathetic activity C) Decreased extracellular fluid potassium ions D) Excess extracellular fluid potassium ions E) Excess extracellular fluid calcium ions
(A) 1 The first heart sound corresponds to closure of the atrial-ventricular valves. Before this closure occurs, the ventricle fills (phase 4 → 1). After the valves close, isovolumetric contraction begins and ventricular pressure increases (phase 1 → 2).
11. The first heart sound corresponds to point (A) 1 (B) 2 (C) 3 (D) 4
E) Pulmonary valve closes At the end of ventricular ejection, both the aortic valves and the pulmonary valves close. This is followed by the period of isovolumic relaxation.
11. Which of the following events occurs at the end of the period of ventricular ejection? A) A-V valves close B) Aortic valve opens C) Aortic valve remains open D) A-V valves open E) Pulmonary valve closes
(C) 5.25 L/min Stroke volume is the volume ejected from the ventricle and is represented on the pressure-volume loop as phase 2 → 3; end-diastolic volume is about 140 mL and end-systolic volume is about 65 mL; the difference, or stroke volume, is 75 mL. Cardiac output is calculated as stroke volume Å~ heart rate or 75 mL Å~ 70 beats/min = 5250 mL/min or 5.25 L/min.
12. If the heart rate is 70 beats/min, then the cardiac output of this ventricle is closest to (A) 3.45 L/min (B) 4.55 L/min (C) 5.25 L/min (D) 8.00 L/min (E) 9.85 L/min
E) Isovolumic contraction Immediately after the QRS wave, the ventricles begin to contract and the first phase that occurs is isovolumic contraction. This occurs before the ejection phase and increases the ventricular pressure enough to mechanically open the aortic and pulmonary valves.
12. Which of the following phases of the cardiac cycle follows immediately after the beginning of the QRS wave? A) Isovolumic relaxation B) Ventricular ejection C) Atrial systole D) Diastasis E) Isovolumic contraction
B) Excess potassium ions in the blood Excess potassium ions in the blood and extracellular fluid cause the heart to become dilated and flaccid as well as slowing the heart. This effect is important due to a more positive resting membrane potential in the cardiac muscle fibers. As the membrane potential becomes more positive, the intensity of the action potential decreases, which makes the contraction of the heart progressively weaker. Excess calcium ions in the blood and sympathetic stimulation and increased norepinephrine concentration of the blood all cause the heart to contract vigorously.
13. Which of the following conditions will result in a dilated, flaccid heart? A) Excess calcium ions in the blood B) Excess potassium ions in the blood C) Excess sodium ions in the blood D) Increased sympathetic stimulation E) Increased norepinephrine concentration in the blood
E) 25 L/min The normal plateau level of the cardiac output function curve is 13 L/min. This level decreases in any kind of cardiac failure and increases markedly during sympathetic stimulation.
14. A 25-year-old, well-conditioned athlete weighs 80 kg (176 lb). During maximal sympathetic stimulation, what is the plateau level of his cardiac output function curve? A) 3 L/min B) 5 L/min C) 10 L/min D) 13 L/min E) 25 L/min
(C) partial occlusion of a blood vessel Turbulent flow is predicted when the Reynolds number is increased. Factors that increase the Reynolds number and produce turbulent flow are decreased viscosity (hematocrit) and increased velocity. Partial occlusion of a blood vessel increases the Reynolds number (and turbulence) because the decrease in crosssectional area results in increased blood velocity (v = Q/A).
15. The tendency for blood flow to be turbulent is increased by (A) increased viscosity (B) increased hematocrit (C) partial occlusion of a blood vessel (D) decreased velocity of blood flow
E) Closing of the A-V valves As seen in Chapter 9, the first heart sound by definition occurs just after the ventricular pressure exceeds the atrial pressure. This causes the A-V valves to mechanically close. The second heart sound occurs when the aortic and pulmonary valves close.
15. Which of the following events is associated with the first heart sound? A) Closing of the aortic valve B) Inrushing of blood into the ventricles during diastole C) Beginning of diastole D) Opening of the A-V valves E) Closing of the A-V valves
(D) a suppressed response of the baroreceptor mechanism Orthostatic hypotension is a decrease in arterial pressure that occurs when a person moves from a supine to a standing position. A person with a normal baroreceptor mechanism responds to a decrease in arterial pressure through the vasomotor center by increasing sympathetic outflow and decreasing parasympathetic outflow. The sympathetic component helps to restore blood pressure by increasing heart rate, contractility, total peripheral resistance (TPR), and mean systemic pressure. In a patient who has undergone a sympathectomy, the sympathetic component of the baroreceptor mechanism is absent.
16. Following a sympathectomy, a 66-yearold man experiences orthostatic hypotension. The explanation for this occurrence is (A) an exaggerated response of the renin-angiotensin-aldosterone system (B) a suppressed response of the renin-angiotensin-aldosterone system (C) an exaggerated response of the baroreceptor mechanism (D) a suppressed response of the baroreceptor mechanism
D) Increased potassium permeability The increase in potassium permeability causes a hyperpolarization of the A-V node, and this will decrease the heart rate. Increases in sodium permeability will actually partially depolarize the A-V node, and an increase in norepinephrine levels increases the heart rate.
16. Which of the following conditions at the A-V node will cause a decrease in heart rate? A) Increased sodium permeability B) Decreased acetylcholine levels C) Increased norepinephrine levels D) Increased potassium permeability E) Increased calcium permeability
D) Releases norepinephrine at the sympathetic endings Increased sympathetic stimulation of the heart increases heart rate, atrial contractility, and ventricular contractility and also increases norepinephrine release at the ventricular sympathetic nerve endings. It does not release acetylcholine. It does cause an increased sodium permeability of the A-V node, which increases the rate of upward drift of the membrane potential to the threshold level for self-excitation, thus increasing heart rate.
17. Sympathetic stimulation of the heart A) Releases acetylcholine at the sympathetic endings B) Decreases sinus nodal discharge rate C) Decreases excitability of the heart D) Releases norepinephrine at the sympathetic endings E) Decreases cardiac contractility
(D) ST segment The PR segment (part of the PR interval) and the ST segment are the only portions of the electrocardiogram (ECG) that are isoelectric. The PR interval includes the P wave (atrial depolarization) and the PR segment, which represents conduction through the atrioventricular (AV) node; during this phase, the ventricles are not yet depolarized. The ST segment is the only isoelectric period when the entire ventricle is depolarized.
17. The ventricles are completely depolarized during which isoelectric portion of the electrocardiogram (ECG)? (A) PR interval (B) QRS complex (C) QT interval (D) ST segment (E) T wave
(C) Left-to-right ventricular shunt In a left-to-right ventricular shunt, a defect in the ventricular septum allows blood to flow from the left ventricle to the right ventricle instead of being ejected into the aorta. The "shunted" fraction of the left ventricular output is therefore added to the output of the right ventricle, making pulmonary blood flow (the cardiac output of the right ventricle) higher than systemic blood flow (the cardiac output of the left ventricle). In normal adults, the outputs of both ventricles are equal in the steady state. In the fetus, pulmonary blood flow is near zero. Right ventricular failure results in decreased pulmonary blood flow. Administration of a positive inotropic agent should have the same effect on contractility and cardiac output in both ventricles.
18. In which of the following situations is pulmonary blood flow greater than aortic blood flow? (A) Normal adult (B) Fetus (C) Left-to-right ventricular shunt (D) Right-to-left ventricular shunt (E) Right ventricular failure (F) Administration of a positive inotropic agent
D) 0.13 sec The impulse from the S-A node travels rapidly through the internodal pathways and arrives at the A-V node at 0.03 sec, at the A-V bundle at 0.12 sec and at the ventricular septum at 0.16 sec. The total delay is thus 0.13 sec.
18. What is the normal total delay of the cardiac impulse in the A-V node plus bundle? A) 0.22 sec B) 0.18 sec C) 0.16 sec D) 0.13 sec E) 0.09 sec
(C) increased mean systemic pressure The shift in the venous return curve to the right is consistent with an increase in blood volume and, as a consequence, mean systemic pressure. Both cardiac output and venous return are increased in the new steady state (and are equal to each other). Contractility is unaffected.
19. The change indicated by the dashed lines on the cardiac output/venous return curves shows (A) decreased cardiac output in the "new" steady state (B) decreased venous return in the "new" steady state (C) increased mean systemic pressure (D) decreased blood volume (E) increased myocardial contractility
D) There is an increased rate of upward drift of the resting membrane potential of the S-A node During sympathetic stimulation, the permeabilities of the S-A node and the A-V node increase. Also, the permeability of cardiac muscle to calcium increases resulting in an increased contractile strength. In addition, there is an upward drift of the resting membrane potential of the S-A node. Increased permeability of the S-A node to potassium does not occur during sympathetic stimulation.
19. Which of the following best explains how sympathetic stimulation affects the heart? A) Permeability of the S-A node to sodium decreases B) Permeability of the A-V node to sodium decreases C) Permeability of the S-A node to potassium increases D) There is an increased rate of upward drift of the resting membrane potential of the S-A node E) Permeability of the cardiac muscle to calcium decreases
(B) Increased contractility When a person moves to a standing position, blood pools in the leg veins, causing decreased venous return to the heart, decreased cardiac output, and decreased arterial pressure. The baroreceptors detect the decrease in arterial pressure, and the vasomotor center is activated to increase sympathetic outflow and decrease parasympathetic outflow. There is an increase in heart rate (resulting in a decreased PR interval), contractility, and total peripheral resistance (TPR). Because both heart rate and contractility are increased, cardiac output will increase toward normal.
2. When a person moves from a supine position to a standing position, which of the following compensatory changes occurs? (A) Decreased heart rate (B) Increased contractility (C) Decreased total peripheral resistance (TPR) (D) Decreased cardiac output (E) Increased PR intervals
(D) decreased conduction through the AV node A pattern of two P waves preceding each QRS complex indicates that only every other P wave is conducted through the atrioventricular (AV) node to the ventricle. Thus, conduction velocity through the AV node must be decreased.
20. A 30-year-old female patient's electrocardiogram (ECG) shows two P waves preceding each QRS complex. The interpretation of this pattern is (A) decreased firing rate of the pacemaker in the sinoatrial (SA) node (B) decreased firing rate of the pacemaker in the atrioventricular (AV) node (C) increased firing rate of the pacemaker in the SA node (D) decreased conduction through the AV node (E) increased conduction through the His- Purkinje system
C) A-V bundle fibers The atrial and ventricular muscles have a relatively rapid rate of conduction of the cardiac action potential, and the anterior internodal pathway also has fairly rapid conduction of the impulse. However, the A-V bundle myofibrils have a slow rate of conduction because their sizes are considerably smaller than the sizes of the normal atrial and ventricular muscle. Also, their slow conduction is partly caused by diminished numbers of gap junctions between successive muscle cells in the conducting pathway, causing a great resistance to conduction of the excitatory ions from one cell to the next.
20. Which of the following structures will have the slowest rate of conduction of the cardiac action potential? A) Atrial muscle B) Anterior internodal pathway C) A-V bundle fibers D) Purkinje fibers E) Ventricular muscle
(A) Decreased firing rate of the carotid sinus nerve A decrease in blood pressure causes decreased stretch of the carotid sinus baroreceptors and decreased firing of the carotid sinus nerve. In an attempt to restore blood pressure, the parasympathetic outflow to the heart is decreased and sympathetic outflow is increased. As a result, heart rate and contractility will be increased. Mean systemic pressure will increase because of increased sympathetic tone of the veins (and a shift of blood to the arteries).
21. An acute decrease in arterial blood pressure elicits which of the following compensatory changes? (A) Decreased firing rate of the carotid sinus nerve (B) Increased parasympathetic outflow tothe heart (C) Decreased heart rate (D) Decreased contractility (E) Decreased mean systemic pressure
A) 0.22 sec After the S-A node discharges, the action potential travels through the atria, through the A-V bundle system and finally to the ventricular septum and throughout the ventricle. The last place that the impulse arrives is at the epicardial surface at the base of the left ventricle, which requires a transit time of 0.22 sec.
21. If the S-A node discharges at 0.00 seconds, when will the action potential normally arrive at the epicardial surface at the base of the left ventricle? A) 0.22 sec B) 0.18 sec C) 0.16 sec D) 0.12 sec E) 0.09 sec
D) 0.12 sec The action potential arrives at the A-V bundle at 0.12 sec. It arrives at the A-V node at 0.03 sec and is delayed 0.09 sec in the A-V node, which results in an arrival time at the bundle of His of 0.12 sec.
22. If the S-A node discharges at 0.00 seconds, when will the action potential normally arrive at the A-V bundle (bundle of His)? A) 0.22 sec B) 0.18 sec C) 0.16 sec D) 0.12 sec E) 0.09 sec
(B) increased venous pressure Edema occurs when more fluid is filtered out of the capillaries than can be returned to the circulation by the lymphatics. Filtration is increased by changes that increase Pc or decrease πc. Arteriolar constriction would decrease Pc and decrease filtration. Dehydration would increase plasma protein concentration (by hemoconcentration) and thereby increase πc and decrease filtration. Increased venous pressure would increase Pc and filtration.
22. The tendency for edema to occur will be increased by (A) arteriolar constriction (B) increased venous pressure (C) increased plasma protein concentration (D) muscular activity
(A) the aortic valve closes before the pulmonic valve The second heart sound is associated with closure of the aortic and pulmonic valves. Because the aortic valve closes before the pulmonic valve, the sound can be split by inspiration.
23. Inspiration "splits" the second heart sound because (A) the aortic valve closes before the pulmonic valve (B) the pulmonic valve closes before the aortic valve (C) the mitral valve closes before the tricuspid valve (D) the tricuspid valve closes before the mitral valve (E) filling of the ventricles has fast and slow components
D) Increased potassium permeability Increases in sodium and calcium permeability at the S-A node result in an increased heart rate. An increased potassium permeability causes a hyperpolarization of the S-A node, which causes the heart rate to decrease.
23. Which of the following conditions at the S-A node will cause heart rate to decrease? A) Increased norepinephrine levels B) Increased sodium permeability C) Increased calcium permeability D) Increased potassium permeability E) Decreased acetylcholine levels
(C) local metabolites on skeletal muscle arterioles During exercise, local metabolites accumulate in the exercising muscle and cause local vasodilation and decreased arteriolar resistance of the skeletal muscle. Because muscle mass is large, it contributes a large fraction of the total peripheral resistance (TPR). Therefore, the skeletal muscle vasodilation results in an overall decrease in TPR, even though there is sympathetic vasoconstriction in other vascular beds.
24. During exercise, total peripheral resistance (TPR) decreases because of the effect of (A) the sympathetic nervous system on splanchnic arterioles (B) the parasympathetic nervous system on skeletal muscle arterioles (C) local metabolites on skeletal muscle arterioles (D) local metabolites on cerebral arterioles (E) histamine on skeletal muscle arterioles
A) Hyperpolarization of the S-A node Acetylcholine does not depolarize the A-V node or increase permeability of the cardiac muscle to calcium ions but causes hyperpolarization of the S-A node and the A-V node by increasing permeability to potassium ions. This results in a decreased heart rate.
24. Which of the following are caused by acetylcholine? A) Hyperpolarization of the S-A node B) Depolarization of the A-V node C) Decreased permeability of the S-A node to potassium ions D) Increased heart rate E) Increased permeability of the cardiac muscle to calcium ions
(A) aortic pressure The electrocardiogram (ECG) tracing serves as a reference. The QRS complex marks ventricular depolarization, followed immediately by ventricular contraction. Aortic pressure increases steeply after QRS, as blood is ejected from the ventricles. After reaching peak pressure, aortic pressure decreases as blood runs off into the arteries. The characteristic dicrotic notch ("blip" in the aortic pressure curve) appears when the aortic valve closes. Aortic pressure continues to decrease as blood flows out of the aorta.
25. Curve A in the figure represents (A) aortic pressure (B) ventricular pressure (C) atrial pressure (D) ventricular volume
A) -40 mV The normal resting membrane potential of the S-A node is !55 mV. As the sodium leaks into the membrane an upward drift of the membrane potential occurs until it reaches !40 mV. This is the threshold level that initiates the action potential at the S-A node.
25. What is the membrane potential (threshold level) at which the S-A node discharges? A) -40 mV B) -55 mV C) -65 mV D) -85 mV E) -105 mV
(D) ventricular volume Ventricular volume increases slightly with atrial systole (P wave), is constant during isovolumetric contraction (QRS), and then decreases dramatically after the QRS, when blood is ejected from the ventricle.
26. Curve B in the figure represents (A) left atrial pressure (B) ventricular pressure (C) atrial pressure (D) ventricular volume
D) Increased potassium permeability An increase in potassium permeability causes a decrease in the membrane potential of the A-V node. Thus, it will be extremely hyperpolarized, making it much more difficult for the membrane potential to reach its threshold level for conduction. This results in a decrease in heart rate. Increases in sodium and calcium permeability and norepinephrine levels increase the membrane potential, causing a tendency to increase the heart rate.
26. Which of the following conditions at the A-V node will cause a decrease in heart rate? A) Increased sodium permeability B) Decreased acetylcholine levels C) Increased norepinephrine levels D) Increased potassium permeability E) Increased calcium permeability
(C) an increase in arterial pressure An increase in arteriolar resistance will increase total peripheral resistance (TPR). Arterial pressure = cardiac output TPR, so arterial pressure will also increase. Capillary filtration decreases when there is arteriolar constriction because Pc decreases. Afterload of the heart would be increased by an increase in TPR.
27. An increase in arteriolar resistance, without a change in any other component of the cardiovascular system, will produce (A) a decrease in total peripheral resistance (TPR) (B) an increase in capillary filtration (C) an increase in arterial pressure (D) a decrease in afterload
A) 30/min If there is a failure in conduction of the S-A nodal impulse to the A-V node or if the S-A node stops firing, the A-V node will take over as the pacemaker of the heart. The intrinsic rhythmical rate of the A-V node is 40 to 60 times per minute. If the Purkinje fibers take over as pacemakers, the heart rate will be between 15 and 40 beats/min.
27. If the ventricular Purkinje fibers become the pacemaker of the heart, what is the expected heart rate? A) 30/min B) 50/min C) 65/min D) 75/min E) 85/min
(D) 6.25 L/min Cardiac output is calculated by the Fick principle if whole body oxygen (O2) consumption and [O2] in the pulmonary artery and pulmonary vein are measured. Mixed venous blood could substitute for a pulmonary artery sample, and peripheral arterial blood could substitute for a pulmonary vein sample. Central venous pressure and heart rate are not needed for this calculation.
28. The following measurements were obtained in a male patient: Central venous pressure: 10 mm Hg Heart rate: 70 beats/min Pulmonary vein [O2] = 0.24 mL O2/mL Pulmonary artery [O2] = 0.16 mL O2/mL Whole body O2 consumption: 500 mL/min What is this patient's cardiac output? (A) 1.65 L/min (B) 4.55 L/min (C) 5.00 L/min (D) 6.25 L/min (E) 8.00 L/min
D) 0.13 sec The impulse coming from the S-A node to the A-V node arrives at 0.03 sec. Then there is a total delay of 0.13 sec in the A-V node and bundle system allowing the impulse to arrive at the ventricular septum at 0.16 sec.
28. What is the normal total delay of the cardiac impulse in the A-V node and the A-V bundle system? A) 0.03 sec B) 0.06 sec C) 0.09 sec D) 0.13 sec E) 0.17 sec
D) -55 mV The resting membrane potential of the sinus nodal fibers is !55 mV, and this is in contrast with the !85 to !90 mV membrane potential of cardiac muscle. Other major differences between the sinus nodal fibers and ventricular muscle fibers are that the sinus fibers exhibit self-excitation from inward leaking of sodium ions.
29. What is the resting membrane potential of the sinus nodal fibers? A) -100 mV B) -90 mV C) -80 mV D) -55 mV E) -20 mV
(B) Upstroke of the action potential in Purkinje fibers The upstroke of the action potential in the atria, ventricles, and Purkinje fibers is the result of a fast inward Na+ current. The upstroke of the action potential in the sinoatrial (SA) node is the result of an inward Ca2+ current. The plateau of the ventricular action potential is the result of a slow inward Ca2+ current. Repolarization in all cardiac tissues is the result of an outward K+ current.
29. Which of the following is the result of an inward Na+ current? (A) Upstroke of the action potential in the sinoatrial (SA) node (B) Upstroke of the action potential in Purkinje fibers (C) Plateau of the action potential in ventricular muscle (D) Repolarization of the action potential in ventricular muscle (E) Repolarization of the action potential in the SA node
(E) Renal artery Pressures on the venous side of the circulation (e.g., central vein, right atrium, renal vein) are lower than pressures on the arterial side. Pressure in the pulmonary artery (and all pressures on the right side of the heart) are much lower than their counterparts on the left side of the heart. In the systemic circulation, systolic pressure is actually slightly higher in the downstream arteries (e.g., renal artery) than in the aorta because of the reflection of pressure waves at branch points.
3. At which site is systolic blood pressure the highest? (A) Aorta (B) Central vein (C) Pulmonary artery (D) Right atrium (E) Renal artery (F) Renal vein
A) 30/min If the Purkinje fibers are the pacemaker of the heart, the heart rate ranges between 15 and 40 beats/min. In contrast, the rate of firing of the A-V nodal fibers are 40 to 60 times a minute, and the sinus node fires at 70 to 80 times per minute. If the sinus node is blocked for some reason, the A-V node will take over as the pacemaker; and if the A-V node is blocked, the Purkinje fibers will take over as the pacemaker of the heart.
30. If the Purkinje fibers, situated distal to the A-V junction, become the pacemaker of the heart, what is the expected heart rate? A) 30/min B) 50/min C) 60/min D) 70/min E) 80/min
(C) increased contractility An upward shift of the cardiac output curve is consistent with an increase in myocardial contractility; for any right atrial pressure (sarcomere length), the force of contraction is increased. Such a change causes an increase in stroke volume and cardiac output. Increased blood volume and increased mean systemic pressure are related and would cause a rightward shift in the venous return curve. A negative inotropic agent would cause a decrease in contractility and a downward shift of the cardiac output curve.
30. The dashed line in the figure illustrates the effect of (A) increased total peripheral resistance (TPR) (B) increased blood volume (C) increased contractility (D) a negative inotropic agent (E) increased mean systemic pressure
E) Increased force of contraction of the ventricles Sympathetic stimulation of the heart normally causes an increased heart rate, increased rate of conduction of the cardiac impulse and increased force of contraction in the atria and ventricles. However, it does not cause acetylcholine release at the sympathetic endings because they contain norepinephrine. Parasympathetic stimulation causes acetylcholine release. The sympathetic nervous system firing increases the permeability of the cardiac muscle fibers, the S-A node, and the A-V node to sodium and calcium.
31. Sympathetic stimulation of the heart normally causes which of the following conditions? A) Acetylcholine release at the sympathetic endings B) Decreased heart rate C) Decreased rate of conduction of the cardiac impulse D) Decreased force of contraction of the atria E) Increased force of contraction of the ventricles
(B) end-diastolic volume End-diastolic volume and right atrial pressure are related and can be used interchangeably.
31. The x-axis in the figure could have been labeled (A) end-systolic volume (B) end-diastolic volume (C) pulse pressure (D) mean systemic pressure (E) heart rate
(E) they have the greatest resistance The decrease in pressure at any level of the cardiovascular system is caused by the resistance of the blood vessels (ΔP = Q Å~ R). The greater the resistance is, the greater the decrease in pressure is. The arterioles are the site of highest resistance in the vasculature. The arterioles do not have the greatest surface area or cross-sectional area (the capillaries do). Velocity of blood flow is lowest in the capillaries, not in the arterioles.
32. The greatest pressure decrease in the circulation occurs across the arterioles because (A) they have the greatest surface area (B) they have the greatest cross-sectional area (C) the velocity of blood flow through them is the highest (D) the velocity of blood flow through them is the lowest (E) they have the greatest resistance
A) left arm By convention, the left arm is the positive electrode for lead I of an EKG.
32. When recording lead I on an EKG, the right arm is the negative electrode, and the positive electrode is the A) left arm B) left leg C) right leg D) left arm + left leg E) right arm + left leg
(D) determined by stroke volume Pulse pressure is the difference between the highest (systolic) and lowest (diastolic) arterial pressures. It reflects the volume ejected by the left ventricle (stroke volume). Pulse pressure increases when the capacitance of the arteries decreases, such as with aging.
33. Pulse pressure is (A) the highest pressure measured in the arteries (B) the lowest pressure measured in the arteries (C) measured only during diastole (D) determined by stroke volume (E) decreased when the capacitance of the arteries decreases (F) the difference between mean arterial pressure and central venous pressure
A) left arm By convention, the left arm is the positive electrode for lead aVL of an EKG.
33. When recording lead aVL on an EKG, the positive electrode is the A) left arm B) left leg C) right leg D) left arm + left leg E) right arm + left leg
E) 0.40 sec The contraction of the ventricles lasts almost from the beginning of the Q wave and continues to the end of the T wave. This interval is called the Q-T interval and ordinarily lasts about 0.35 sec. In this particular example the Q-T interval is a little bit longer than average and equals 0.40 sec.
34. A 70-year-old man was had the following EKG during his annual physical exam. What is his Q-T interval? A) 0.12 secterm-115 B) 0.16 sec C) 0.22 sec D) 0.30 sec E) 0.40 sec
(B) an increase in Na+ conductance Phase 4 depolarization is responsible for the pacemaker property of sinoatrial (SA) nodal cells. It is caused by an increase in Na+ conductance and an inward Na+ current (If), which depolarizes the cell membrane.
34. In the sinoatrial (SA) node, phase 4 depolarization (pacemaker potential) is attributable to (A) an increase in K+ conductance (B) an increase in Na+ conductance (C) a decrease in Cl− conductance (D) a decrease in Ca2+ conductance (E) simultaneous increases in K+ and Cl− conductances
B) 70 The heart rate can be calculated by 60 divided by the R-R interval, which is 0.86 sec. This results in a heart rate of 70 beats/min
35. What is the heart rate in the following EKG? A) 64 B) 70 C) 88 D) 94 E) 104
(A) α1 Receptors The α1 receptors for norepinephrine are excitatory on vascular smooth muscle and cause vasoconstriction. There are also β2 receptors on the arterioles of skeletal muscle, but they produce vasodilation.
35. Which receptor mediates constriction of arteriolar smooth muscle? (A) α1 Receptors (B) β1 Receptors (C) β2 Receptors (D) Muscarinic receptors
(D) Reduced ventricular ejection Aortic pressure reaches its highest level immediately after the rapid ejection of blood during left ventricular systole. This highest level actually coincides with the beginning of the reduced ventricular ejection phase.
36. During which phase of the cardiac cycle is aortic pressure highest? (A) Atrial systole (B) Isovolumetric ventricular contraction (C) Rapid ventricular ejection (D) Reduced ventricular ejection (E) Isovolumetric ventricular relaxation (F) Rapid ventricular filling (G) Reduced ventricular filling (diastasis)
E) 0.35 seconds The contraction of the ventricles lasts almost from the beginning of the Q wave and continues to the end of the T wave. This interval is called the Q-T interval and ordinarily lasts about 0.35 sec.
36. What is the normal QT interval? A) 0.03 seconds B) 0.13 seconds C) 0.16 seconds D) 0.20 seconds E) 0.35 seconds
(C) Ca2+ Contractility of myocardial cells depends on the intracellular [Ca2+], which is regulated by Ca2+ entry across the cell membrane during the plateau of the action potential and by Ca2+ uptake into and release from the sarcoplasmic reticulum (SR). Ca2+ binds to troponin C and removes the inhibition of actin-myosin interaction, allowing contraction (shortening) to occur.
37. Myocardial contractility is best correlated with the intracellular concentration of (A) Na+ (B) K+ (C) Ca2+ (D) Cl− (E) Mg2+
B) left leg By convention, the left leg is the positive electrode for lead II of an EKG.
37. When recording lead II on an EKG, the positive electrode is the A) left arm B) left leg C) right leg D) left arm + left leg E) right arm + left leg
A) left arm By convention, the left arm is the negative electrode for lead III of an EKG.
38. When recording lead III on an EKG, the negative electrode is the A) left arm B) left leg C) right leg D) left arm + left leg E) right arm + left leg
(B) Vasodilation of the arterioles Histamine causes vasodilation of the arterioles, which increases Pc and capillary filtration. It also causes constriction of the veins, which contributes to the increase in Pc. Acetylcholine (ACh) interacts with muscarinic receptors (although these are not present on vascular smooth muscle).
38. Which of the following is an effect of histamine? (A) Decreased capillary filtration (B) Vasodilation of the arterioles (C) Vasodilation of the veins (D) Decreased Pc (E) Interaction with the muscarinic receptors on the blood vessels
D) 2.0 mV Einthoven's law states that the voltage in lead I plus the voltage in lead III is equal to the voltage in lead II, which in this case is 2.0 mV.
39. A 65-year-old man had an EKG recorded at a local emergency room following a biking accident. His weight was 80 kg and his aortic blood pressure was 160/90 mm Hg. The QRS voltage was 0.5 mV in lead I and 1.5 mV in lead III. What is the QRS voltage in lead II? A) 0.5 mV B) 1.0 mV C) 1.5 mV D) 2.0 mV E) 2.5 mV
(C) Brain Blood flow to the brain is autoregulated by the PCO2. If metabolism increases (or arterial pressure decreases), the PCO2 will increase and cause cerebral vasodilation. Blood flow to the heart and to skeletal muscle during exercise is also regulated metabolically, but adenosine and hypoxia are the most important vasodilators for the heart. Adenosine, lactate, and K+ are the most important vasodilators for exercising skeletal muscle. Blood flow to the skin is regulated by the sympathetic nervous system rather than by local metabolites.
39. Carbon dioxide (CO2) regulates blood flow to which one of the following organs? (A) Heart (B) Skin (C) Brain (D) Skeletal muscle at rest (E) Skeletal muscle during exercise
(B) atrioventricular (AV) node The absent P wave indicates that the atrium is not depolarizing and, therefore, the pacemaker cannot be in the sinoatrial (SA) node. Because the QRS and T waves are normal, depolarization and repolarization of the ventricle must be proceeding in the normal sequence. This situation can occur if the pacemaker is located in the atrioventricular (AV) node. If the pacemaker were located in the bundle of His or in the Purkinje system, the ventricles would activate in an abnormal sequence (depending on the exact location of the pacemaker) and the QRS wave would have an abnormal configuration. Ventricular muscle does not have pacemaker properties.
4. A person's electrocardiogram (ECG) has no P wave, but has a normal QRS complex and a normal T wave. Therefore, his pacemaker is located in the (A) sinoatrial (SA) node (B) atrioventricular (AV) node (C) bundle of His (D) Purkinje system (E) ventricular muscle
E) aVF As can be seen in Figure 12-3 (TMP12), the positive portion of lead aVF has an axis of 90° and the negative part of this lead has an axis of !90°. Note the difference between the positive and the negative ends of this vector is 180°.
40. A ventricular depolarization wave when traveling -90° in the frontal plane will cause a large negative deflection in which lead? A) aVR B) aVL C) Lead II D) Lead III E) aVF
(D) 100% Cardiac output of the left and right sides of the heart is equal. Blood ejected from the left side of the heart to the systemic circulation must be oxygenated by passage through the pulmonary circulation.
40. Cardiac output of the right side of the heart is what percentage of the cardiac output of the left side of the heart? (A) 25% (B) 50% (C) 75% (D) 100% (E) 125%
(C) filling of the ventricles The atrioventricular (AV) delay (which corresponds to the PR interval) allows time for filling of the ventricles from the atria. If the ventricles contracted before they were filled, stroke volume would decrease.
41. The physiologic function of the relatively slow conduction through the atrioventricular (AV) node is to allow sufficient time for (A) runoff of blood from the aorta to the arteries (B) venous return to the atria (C) filling of the ventricles (D) contraction of the ventricles (E) repolarization of the ventricles
(A) Skin Circulation of the skin is controlled primarily by the sympathetic nerves. The coronary and cerebral circulations are primarily regulated by local metabolic factors. Skeletal muscle circulation is regulated by metabolic factors (local metabolites) during exercise, although at rest it is controlled by the sympathetic nerves.
42. Blood flow to which organ is controlled primarily by the sympathetic nervous system rather than by local metabolites? (A) Skin (B) Heart (C) Brain (D) Skeletal muscle during exercise
(E) Total peripheral resistance (TPR) In anticipation of exercise, the central command increases sympathetic outflow to the heart and blood vessels, causing an increase in heart rate and contractility. Venous return is increased by muscular activity and contributes to an increase in cardiac output by the Frank-Starling mechanism. Pulse pressure is increased because stroke volume is increased. Although increased sympathetic outflow to the blood vessels might be expected to increase total peripheral resistance (TPR), it does not because there is an overriding vasodilation of the skeletal muscle arterioles as a result of the buildup of vasodilator metabolites (lactate, K+, adenosine). Because this vasodilation improves the delivery of O2, more O2 can be extracted and used by the contracting muscle.
43. Which of the following parameters is decreased during moderate exercise? (A) Arteriovenous O2 difference (B) Heart rate (C) Cardiac output (D) Pulse pressure (E) Total peripheral resistance (TPR)
(B) β1 Receptors Propranolol is an adrenergic antagonist that blocks both β1 and β2 receptors. When propanolol is administered to reduce cardiac output, it inhibits β1 receptors in the sinoatrial (SA) node (heart rate) and in ventricular muscle (contractility).
44. When propranolol is administered, blockade of which receptor is responsible for the decrease in cardiac output that occurs? (A) α1 Receptors (B) β1 Receptors (C) β2 Receptors (D) Muscarinic receptors (E) Nicotinic receptors
(E) Isovolumetric ventricular relaxation Ventricular volume is at its lowest value while the ventricle is relaxed (diastole), just before ventricular filling begins.
45. During which phase of the cardiac cycle is ventricular volume lowest? (A) Atrial systole (B) Isovolumetric ventricular contraction (C) Rapid ventricular ejection (D) Reduced ventricular ejection (E) Isovolumetric ventricular relaxation (F) Rapid ventricular filling (G) Reduced ventricular filling (diastasis)
(D) Increased size of the heart Myocardial O2 consumption is determined by the amount of tension developed by the heart. It increases when there are increases in aortic pressure (increased afterload), when there is increased heart rate or stroke volume (which increases cardiac output), or when the size (radius) of the heart is increased (T = P Å~ r). Influx of Na+ ions during an action potential is a purely passive process, driven by the electrochemical driving forces on Na+ ions. Of course, maintenance of the inwardly directed Na+ gradient over the long term requires the Na+−K+ pump, which is energized by adenosine triphosphate (ATP).
46. Which of the following changes will cause an increase in myocardial O2 consumption? (A) Decreased aortic pressure (B) Decreased heart rate (C) Decreased contractility (D) Increased size of the heart (E) Increased influx of Na+ during the upstroke of the action potential
(D) Glucose Because O2, CO2, and CO are lipophilic, they cross capillary walls primarily by diffusion through the endothelial cell membranes. Glucose is watersoluble; it cannot cross through the lipid component of the cell membrane and is restricted to the water-filled clefts, or pores, between the cells.
47. Which of the following substances crosses capillary walls primarily through water-filled clefts between the endothelial cells? (A) O2 (B) CO2 (C) CO (D) Glucose
(E) Decreased venous return Diarrhea causes a loss of extracellular fluid volume, which produces a decrease in arterial pressure. The decrease in arterial pressure activates the baroreceptor mechanism, which produces an increase in heart rate when the patient is supine. When she stands up, blood pools in her leg veins and produces a decrease in venous return, a decrease in cardiac output (by the Frank-Starling mechanism), and a further decrease in arterial pressure. The further decrease in arterial pressure causes further activation of the baroreceptor mechanism and a further increase in heart rate.
48. A 24-year-old woman presents to the emergency department with severe diarrhea. When she is supine (lying down), her blood pressure is 90/60 mm Hg (decreased) and her heart rate is 100 beats/min (increased). When she is moved to a standing position, her heart rate further increases to 120 beats/min. Which of the followingaccounts for the further increase in heart rate upon standing? (A) Decreased total peripheral resistance (B) Increased venoconstriction (C) Increased contractility (D) Increased afterload (E) Decreased venous return
(D) Left renal artery stenosis In this patient, hypertension is most likely caused by left renal artery stenosis, which led to increased renin secretion by the left kidney. The increased plasma renin activity causes an increased secretion of aldosterone, which increases Na+ reabsorption by the renal distal tubule. The increased Na+ reabsorption leads to increased blood volume and blood pressure. The right kidney responds to the increase in blood pressure by decreasing its renin secretion. Right renal artery stenosis causes a similar pattern of results, except that renin secretion from the right kidney, not the left kidney, is increased. Aldosterone-secreting tumors cause increased levels of aldosterone, but decreased plasma renin activity (as a result of decreased renin secretion by both kidneys). Pheochromocytoma is associated with increased circulating levels of catecholamines, which increase blood pressure by their effects on the heart (increased heart rate and contractility) and blood vessels (vasoconstriction); the increase in blood pressure is sensed by the kidneys and results in decreased plasma renin activity and aldosterone levels.
49. A 60-year-old businessman is evaluated by his physician, who determines that his blood pressure is significantly elevated at 185/130 mm Hg. Laboratory tests reveal an increase in plasma renin activity, plasma aldosterone level, and left renal vein renin level. His right renal vein renin level is decreased. What is the most likely cause of the patient's hypertension? (A) Aldosterone-secreting tumor (B) Adrenal adenoma secreting aldosterone and cortisol (C) Pheochromocytoma (D) Left renal artery stenosis (E) Right renal artery stenosis
(C) heart rate An increase in ejection fraction means that a higher fraction of the end-diastolic volume is ejected in the stroke volume (e.g., because of the administration of a positive inotropic agent). When this situation occurs, the volume remaining in the ventricle after systole, the end-systolic volume, will be reduced. Cardiac output, pulse pressure, stroke volume, and systolic pressure will be increased.
5. If the ejection fraction increases, there will be a decrease in (A) cardiac output (B) end-systolic volume (C) heart rate (D) pulse pressure (E) stroke volume (F) systolic pressure
D) 3 During phase 3 of the ventricular muscle action potential, the potassium permeability of ventricular muscle greatly increases, which causes a more negative membrane potential.
5. In which phase of the ventricular muscle action potential is the potassium permeability the highest? A) 0 B) 1 C) 2 D) 3 E) 4
(E) Phase 4 Phase 4 is the resting membrane potential. Because the conductance to K+ is highest, the membrane potential approaches the equilibrium potential for K+.
50. During which phase of the ventricular action potential is the membrane potential closest to the K+ equilibrium potential? (A) Phase 0 (B) Phase 1 (C) Phase 2 (D) Phase 3 (E) Phase 4
(C) Phase 2 Phase 2 is the plateau of the ventricular action potential. During this phase, the conductance to Ca2+ increases transiently. Ca2+ that enters the cell during the plateau is the trigger that releases more Ca2+ from the sarcoplasmic reticulum (SR) for the contraction.
51. During which phase of the ventricular action potential is the conductance to Ca2+ highest? (A) Phase 0 (B) Phase 1 (C) Phase 2 (D) Phase 3 (E) Phase 4
(E) Phase 4 Phase 4 is electrical diastole.
52. Which phase of the ventricular action potential coincides with diastole? (A) Phase 0 (B) Phase 1 (C) Phase 2 (D) Phase 3 (E) Phase 4
(A) Decreases heart rate Propranolol, a β-adrenergic antagonist, blocks all sympathetic effects that are mediated by a β1 or β2 receptor. The sympathetic effect on the sinoatrial (SA) node is to increase heart rate via a β1 receptor; therefore, propranolol decreases heart rate. Ejection fraction reflects ventricular contractility, which is another effect of β1 receptors; thus, propranolol decreases contractility, ejection fraction, and stroke volume. Splanchnic and cutaneous resistance are mediated by α1 receptors.
53. Propranolol has which of the following effects? (A) Decreases heart rate (B) Increases left ventricular ejection fraction (C) Increases stroke volume (D) Decreases splanchnic vascular resistance (E) Decreases cutaneous vascular resistance
(D) Muscarinic receptors Acetylcholine (ACh) causes slowing of the heart via muscarinic receptors in the sinoatrial (SA) node.
54. Which receptor mediates slowing of the heart? (A) α1 Receptors (B) β1 Receptors (C) β2 Receptors (D) Muscarinic receptors
(D) Acetylcholine (ACh) A negative inotropic effect is one that decreases myocardial contractility. Contractility is the ability to develop tension at a fixed muscle length. Factors that decrease contractility are those that decrease the intracellular [Ca2+]. Increasing heart rate increases intracellular [Ca2+] because more Ca2+ ions enter the cell during the plateau of each action potential. Sympathetic stimulation and norepinephrine increase intracellular [Ca2+] by increasing entry during the plateau and increasing the storage of Ca2+ by the sarcoplasmic reticulum (SR) [for later release]. Cardiac glycosides increase intracellular [Ca2+] by inhibiting the Na+-K+ pump, thereby inhibiting Na+-Ca2+ exchange (a mechanism that pumps Ca2+ out of the cell). Acetylcholine (ACh) has a negative inotropic effect on the atria.
55. Which of the following agents or changes has a negative inotropic effect on the heart? (A) Increased heart rate (B) Sympathetic stimulation (C) Norepinephrine (D) Acetylcholine (ACh) (E) Cardiac glycosides
(A) gap junctions The gap junctions occur at the intercalated disks between cells and are low-resistance sites of current spread.
56. The low-resistance pathways between myocardial cells that allow for the spread of action potentials are the (A) gap junctions (B) T tubules (C) sarcoplasmic reticulum (SR) (D) intercalated disks (E) mitochondria
(A) Aldosterone Angiotensin I and aldosterone are increased in response to a decrease in renal perfusion pressure. Angiotensinogen is the precursor for angiotensin I. Antidiuretic hormone (ADH) is released when atrial receptors detect a decrease in blood volume. Of these, only aldosterone increases Na+ reabsorption. Atrial natriuretic peptide is released in response to an increase in atrial pressure, and an increase in its secretion would not be anticipated after blood loss.
57. Which agent is released or secreted after a hemorrhage and causes an increase in renal Na+ reabsorption? (A) Aldosterone (B) Angiotensin I (C) Angiotensinogen (D) Antidiuretic hormone (ADH) (E) Atrial natriuretic peptide
(E) Isovolumetric ventricular relaxation The mitral [atrioventricular (AV)] valve opens when left atrial pressure becomes higher than left ventricular pressure. This situation occurs when the left ventricular pressure is at its lowest level—when the ventricle is relaxed, blood has been ejected from the previous cycle, and before refilling has occurred.
58. During which phase of the cardiac cycle does the mitral valve open? (A) Atrial systole (B) Isovolumetric ventricular contraction (C) Rapid ventricular ejection (D) Reduced ventricular ejection (E) Isovolumetric ventricular relaxation (F) Rapid ventricular filling (G) Reduced ventricular filling (diastasis)
(D) 92 mL First, calculate stroke volume from the cardiac output and heart rate: Cardiac output = stroke volume Å~ heart rate; thus, stroke volume = cardiac output/heart rate = 3500 mL/95 beats/min = 36.8 mL. Then, calculate end-diastolic volume from stroke volume and ejection fraction: Ejection fraction = stroke volume/end-diastolic volume; thus end-diastolic volume = stroke volume/ejection fraction = 36.8 mL/0.4 = 92 mL.
59. A hospitalized patient has an ejection fraction of 0.4, a heart rate of 95 beats/min, and a cardiac output of 3.5 L/min. What is the patient's end-diastolic volume? (A) 14 mL (B) 37 mL (C) 55 mL (D) 92 mL (E) 140 mL
D) 60% The typical ejection fraction is 60%, and lower values are indicative of a weakened heart.
6. In a resting adult, the typical ventricular ejection fraction has what value? A) 20% B) 30% C) 40% D) 60% E) 80%
D) 200 ml The end diastolic volume is always greater than the end systolic volume. Multiplication of the ejection fraction by the end diastolic volume gives you the stroke volume, which is 50 ml in this problem. Therefore, the end diastolic volume is 50 ml greater than the end systolic volume and has a value of 200 ml.
7. A 30-year-old man has an ejection fraction of 0.25 and an end systolic volume of 150 ml. What is his end diastolic volume? A) 50 ml B) 100 ml C) 125 ml D) 200 ml E) 250 ml
(A) increased cardiac output for a given end-diastolic volume An increase in contractility produces an increase in cardiac output for a given end-diastolic volume, or pressure. The Frank-Starling relationship demonstrates the matching of cardiac output (what leaves the heart) with venous return (what returns to the heart). An increase in contractility (positive inotropic effect) will shift the curve upward.
8. An increase in contractility is demonstrated on a Frank-Starling diagram by (A) increased cardiac output for a given end-diastolic volume (B) increased cardiac output for a given end-systolic volume (C) decreased cardiac output for a given end-diastolic volume (D) decreased cardiac output for a given end-systolic volume
B) The strength and contraction of cardiac muscle depends on the amount of calcium surrounding cardiac myocytes The cardiac muscle stores much more calcium in its tubular system than skeletal muscle and is much more dependent on extracellular calcium than the skeletal muscle. An abundance of calcium is bound by the mucopolysaccharides inside the T-tubule. This calcium is necessary for contraction of cardiac muscle, and its strength of contraction depends on the calcium concentration surrounding the cardiac myocytes. At the initiation of the action potential, the fast sodium channels open first, followed later by the opening of the slow calcium channels.
8. Which of the following statements about cardiac muscle is most accurate? A) The T-tubules of cardiac muscle can store much less calcium than T-tubules in skeletal muscle B) The strength and contraction of cardiac muscle depends on the amount of calcium surrounding cardiac myocytes C) In cardiac muscle the initiation of the action potential causes an immediate opening of slow calcium channels D) Cardiac muscle repolarization is caused by opening of sodium channels E) Mucopolysaccharides inside the T-tubules bind chloride ions
A) He has fever Heart rate is determined by the formula 60/R-R interval, and the heart rate for this patient is 109 beats/ min. This is a fast heart rate, which would occur during fever. A trained athlete has a low heart rate. Excess parasympathetic stimulation and hyperpolarization of the S-A node both decrease heart rate.
9. A 60-year-old man's EKG shows that he has an R-R interval of 0.55 sec. Which of the following best explains his condition? A) He has fever B) He has a normal heart rate C) He has excess parasympathetic stimulation of the S-A node D) He is a trained athlete at rest E) He has hyperpolarization of the S-A node
(B) 1 → 2
9. On the graph showing left ventricular volume and pressure, isovolumetric contraction occurs from point (A) 4 → 1 (B) 1 → 2 (C) 2 → 3 (D) 3 → 4
B) 50° The mean electrical axis can be determined plotting the resultant voltage of the QRS for leads I, II, and III. The result is as is shown above and has a value of -50°.
A 60-year-old woman had the following EKG recorded at a local emergency room following an automobile accident. Her weight was 70 kg and her aortic blood pressure was 140/80 mm Hg. 41. What is the mean electrical axis calculated from standard leads I, II, and III shown in her EKG? A) -90° B) -50° C) -12° D) +100° E) +170°
A) At point D During the ejection phase, the aortic and pulmonary valves open and blood flows into the aorta and pulmonary artery. The ejection phase is between C and D, so the aortic and pulmonary valves open at C and then close at D. The closing of these valves causes the second heart sound.
A 60-year-old woman has a resting heart rate of 70 beats/ min, arterial pressure is 130/85 mm Hg, and body temperature is normal. Her pressure-volume diagram of the left ventricle is shown above. 2. When does the second heart sound occur in the ventricular pressure-volume relationship? A) At point D B) Between point A and point B C) Between point B and point C D) Between point C and point D E) Between point D and point A
B) Between point A and point B Between points A and B is the period of ventricular filling. The vibration of the ventricular walls makes this sound after sufficient blood has entered the ventricular chambers.
A 60-year-old woman has a resting heart rate of 70 beats/ min, arterial pressure is 130/85 mm Hg, and body temperature is normal. Her pressure-volume diagram of the left ventricle is shown above. 3. When does the third heart sound occur in the ventricular pressure-volume relationship? A) At point D B) Between point A and point B C) Between point B and point C D) Between point C and point D E) Between point D and point A
D) 67% The ejection fraction is the stroke volume/end diastolic volume. Stroke volume is 100 ml, and the end systolic volume at point D is 150 ml. This gives you an ejection fraction of 0.667 or in terms of percentage 66.7%.
A 60-year-old woman has a resting heart rate of 70 beats/ min, arterial pressure is 130/85 mm Hg, and body temperature is normal. Her pressure-volume diagram of the left ventricle is shown above. 4. What is her ventricular ejection fraction? A) 33% B) 50% C) 60% D) 67% E) 80%
E) 7000 This patient has a heart rate of 70 beats/, and you can determine the cardiac output by using the following formula: cardiac output # heart rate $ stroke volume. The stroke volume can be determined from the figure, which is 100 ml, the volume change during the C-D segment. Using this you can determine that the cardiac output is 7000 ml/min.
A 60-year-old woman has a resting heart rate of 70 beats/ min, arterial pressure is 130/85 mm Hg, and body temperature is normal. Her pressure-volume diagram of the left ventricle is shown above. 1. What is her cardiac output in milliliters per minute? A) 2000 B) 3000 C) 4000 D) 6000 E) 7000
(D) decreased pulse pressure because stroke volume is decreased On the extrasystolic beat, pulse pressure decreases because there is inadequate ventricular filling time—the ventricle beats "too soon." As a result, stroke volume decreases.
An electrocardiogram (ECG) on a person shows ventricular extrasystoles. 6. The extrasystolic beat would produce (A) increased pulse pressure because contractility is increased (B) increased pulse pressure because heart rate is increased (C) decreased pulse pressure because ventricular filling time is increased (D) decreased pulse pressure because stroke volume is decreased (E) decreased pulse pressure because the PR interval is increased
(A) increased pulse pressure because the contractility of the ventricle is increased The postextrasystolic contraction produces increased pulse pressure because contractility is increased. Extra Ca2+ enters the cell during the extrasystolic beat. Contractility is directly related to the amount of intracellular Ca2+ available for binding to troponin C.
An electrocardiogram (ECG) on a person shows ventricular extrasystoles. 7. After an extrasystole, the next "normal" ventricular contraction produces (A) increased pulse pressure because the contractility of the ventricle is increased (B) increased pulse pressure because total peripheral resistance (TPR) is decreased (C) increased pulse pressure because compliance of the veins is decreased (D) decreased pulse pressure because the contractility of the ventricle is increased term-29 (E) decreased pulse pressure because TPR is decreased
(D) Filtration; 9 mm Hg The net driving force can be calculated with the Starling equation. Because the net pressure is positive, filtration out of the capillary will occur.
In a capillary, Pc is 30 mm Hg, Pi is -2 mm Hg, πc is 25 mm Hg, and πi is 2 mm Hg. 13. What is the direction of fluid movement and the net driving force? (A) Absorption; 6 mm Hg (B) Absorption; 9 mm Hg (C) Filtration; 6 mm Hg (D) Filtration; 9 mm Hg (E) There is no net fluid movement
(C) 4.50 mL/min Kf is the filtration coefficient for the capillary and describes the intrinsic water permeability.
In a capillary, Pc is 30 mm Hg, Pi is -2 mm Hg, πc is 25 mm Hg, and πi is 2 mm Hg. 14. If Kf is 0.5 mL/min/mm Hg, what is the rate of water flow across the capillary wall? (A) 0.06 mL/min (B) 0.45 mL/min (C) 4.50 mL/min (D) 9.00 mL/min (E) 18.00 mL/min
