Physiology - An Illustrated Review

Questions & Answers

Review Questions

1. Which of the following observations shows that the heart rate at rest is predominantly under parasympathetic control?

A.   A totally denervated heart has a resting rate of 100 beats/min.

B.   Cutting the sympathetic efferent supply to the heart causes an increase in the heart rate.

C.   Administering a β-adrenergic antagonist, such as propranolol, causes the heart rate to increase.

D.   Infusion of norepinephrine increases heart rate.

E.   Cutting the parasympathetic efferent fibers to the heart causes a large increase in the heart rate.

2. Which of the following classes of drugs would cause an increased heart rate?

A.   Alpha-adrenergic blocking drug

B.   Beta-adrenergic blocking drug

C.   Cholinergic blocking drug

D.   Cholinergic stimulating drug

E.   Nitrovasodilator drug

3. What process is associated with phase 0 of the ventricular action potential?

A.   Rapid filling of the ventricle

B.   The membrane is at the resting potential between excitations.

C.   Propagation through the Purkinje network

D.   Calcium release from the sarcoplasmic reticulum

E.   Entry of sodium through voltage-gated channels

4. The relatively long plateau of ventricular action potentials coincides with which portion of the ECG?

A.   P wave

B.   PQ interval

C.   Q wave

D.   ST segment

E.   T wave

5. Cardiac glycosides, such as digitalis, enhance the contractile performance of cardiac muscle fibers by

A.   inhibiting the Na+−K+ ATPase of cell membranes.

B.   stimulating intracellular production of cyclic adenosine mono-phosphate (cAMP).

C.   decreasing the amount of Ca2+ available to myofibrils.

D.   stimulating cardiac β1-adrenergic receptors.

E.   blocking cardiac muscarinic receptors.

6. Cardiac output (CO) can be defined by which three parameters?

A.   Heart rate; aortic pressure; end-diastolic volume

B.   Heart rate; end-systolic pressure; end-diastolic pressure

C.   R wave-to-R wave interval; end-diastolic volume; end-systolic volume

D.   Total peripheral resistance (TPR); pulse pressure; stroke volume

E.   TPR; central venous pressure; diastolic pressure

7. Which of the following is the best index of cardiac O2 demand?

A.   Stroke volume multiplied by heart rate

B.   Systolic pressure minus diastolic pressure

C.   Diastolic pressure multiplied by heart rate

D.   Stroke work multiplied by heart rate

E.   Stroke volume multiplied by systolic pressure

8. A well-adjusted 45-year-old woman saw her family physician after experiencing episodes of headache, sweating, and heart “pounding” in her chest (heart rate 125−135/min; blood pressure 172/116 mm Hg). She reported feeling “antsy” and jittery. A urine sample showed elevated levels of metanephrines, which are metabolites of epinephrine. She is diagnosed with having a pheochromocytoma, a tumor of adrenal medullary tissue. It releases catecholamines in an unregulated manner, often episodically. The tumor also releases high levels of metanephrines. Why did the patient experience elevated heart rate and MAP?

A.   Actions of androgenic steroids

B.   Massive firing of the parasympathetic nervous system

C.   Actions of epinephrine and norepinephrine

D.   Actions of aldosterone

E.   Actions of corticosteroids

9. What is the effect of a constant intravenous (IV) infusion of norepinephrine?

A.   A decrease in TPR

B.   An increase in venous volume

C.   An increase in cardiac contractility

D.   A reflexively mediated increase in heart rate

E.   A decrease in afterload

10. A patient has an acute bout of reduced coronary blood flow, causing chest discomfort and weakness. Which treatment is not appropriate?

A.   Nitrovasodilators

B.   Beta-receptor antagonists

C.   IV norepinephrine

D.   Supplemental O2

E.   Calcium channel blockers

11. Which mechanical event of the cardiac cycle is most closely associated in time with the P wave of the electrocardiogram (ECG)?

A.   Rapid diastolic filling

B.   Rapid systolic ejection

C.   Atrial contraction

D.   Atrial relaxation

E.   The start of ventricular contraction

12. Aortic pressure is greatest at which point during the cardiac cycle?

A.   When the aortic valve opens

B.   When the aortic valve closes

C.   The beginning of rapid ventricular filling

D.   The beginning of isovolumetric contraction

E.   The end of rapid ventricular ejection

13. In a normal cardiac cycle,

A.   the maximum and minimum left ventricular pressures are virtually the same as systolic and diastolic pressures measured in a peripheral artery.

B.   left ventricular pressure rises continuously during filling.

C.   > 90% of the end-diastolic volume is ejected.

D.   l eft ventricular pressure is greater than left atrial pressure at all stages of the cycle.

E.   the mitral valve is open longer than is the aortic valve.

14. In adults, what is the result of an uncorrected congenital ventricular septal defect?

A.   Low right ventricular pressure during diastole

B.   Right ventricular stroke volume is larger than left ventricular stroke volume.

C.   A low partial pressure of oxyen (PO2) in systemic arterial blood

D.   A drop in pulmonary artery pressure

E.   A clear diastolic murmur

15. Which of the following might be expected to occur in a patient suffering from moderate right ventricular heart failure?

A.   Pulmonary edema

B.   Raised central venous pressure

C.   Increased systemic arterial blood pressure

D.   Lower right ventricular stroke volume compared with left ventricular stroke volume

E.   Enlarged left atrium

16. Most of the drop in pressure between the ascending aorta and the right atrium occurs across which vessel (s)?

A.   Peripheral arteries

B.   Arterioles

C.   Capillaries

D.   Peripheral veins

E.   Inferior vena cava

17. Why does an aging hypertensive patient often have a large pulse pressure?

A.   Because of low compliance of arterial walls

B.   Because typical drug therapy elevates heart rate

C.   Because of a very large stroke volume

D.   Because the heart is usually hypertrophic

E.   Because the TPR is decreased

18. Five-year-old children have a CO much smaller than normal adults. Both may have similar arterial blood pressures. As a result of normal growth, what change over time would you expect?

A.   The conductance to flow through individual arterioles increases.

B.   TPR decreases.

C.   The resistance to flow offered by the aorta increases.

D.   Heart rate increases.

E.   CO and TPR both increase.

19. What is the calculated vascular resistance to blood flow through the kidneys from the following data? Systolic arterial pressure = 130 mm Hg, diastolic arterial pressure = 70 mm Hg, mean renal venous pressure = 10 mm Hg, renal blood flow = 800 mL/min, renal arterial compliance = 4 mL/mm Hg.

A.   0.1 mm Hg/mL/min

B.   1.3 mm Hg/mL/min

C.   8.0 mm Hg/mL/min

D.   100 mm Hg/mL/min

E.   200 mm Hg/mL/min

20. Therapy for the treatment of essential hypertension might include which of the following?

A.   Administration of a drug that causes the kidney to retain salt

B.   IV infusion of renin substrate (angiotensinogen)

C.   IV administration of acetylcholine

D.   Administration of an antagonist of adenosine receptor sites

E.   Administration of an α-adrenergic antagonist

21. Which of the following statements is true regarding the cardiovascular effects of a drug that causes selective dilation of peripheral arterioles?

A.   The activity in the carotid sinus nerves would likely increase.

B.   The heart rate would increase above normal.

C.   Arterial blood volume would be greater than before administration of the drug.

D.   Sympathetic adrenergic activity to the splanchnic region would be lower than normal.

E.   Venous pressure decreases.

22. An adult stranded in a desert has had no food or water for 2 days. Which statement is true concerning this condition?

A.   Below normal blood concentration of aldosterone

B.   High rate of firing of the carotid sinus nerves

C.   Renin secretion greater than normal

D.   Low circulating levels of vasopressin

E.   Low blood volume due to increased filtration pressure in the capillaries

23. Distention of the low-pressure mechanoreceptors located at the venoatrial junctions

A.   reduces the release of atrial natriuretic peptide (ANP).

B.   increases plasma renin.

C.   relaxes renal arterioles.

D.   stimulates smooth muscle contraction in the walls of large veins.

E.   causes vasoconstriction in the coronary circulation.

24. Filtration of fluid across capillary walls

A.   increases when arterioles vasoconstrict.

B.   is greater at the venule end than at the arteriolar end of the capillary.

C.   increases when large venules dilate.

D.   increases when plasma oncotic pressure is below normal.

E.   is promoted in cases of severe dehydration.

25. Edema can occur as a result of

A.   decreased mean capillary pressure.

B.   persistent, tonic contraction of precapillary sphincters.

C.   decreased albumin concentration of blood plasma.

D.   increased hydrostatic pressure in the interstitial fluid space.

E.   decreased venous pressure.

26. In a healthy adult, the pulmonary artery pressure cycles between 25 and 8 mm Hg, with a mean pressure of 15 mm Hg. What are the likely respective systolic and diastolic pressures of the right ventricle?

A.   25/2 mm Hg

B.   25/8 mm Hg

C.   25/15 mm Hg

D.   15/−2 mm Hg

E.   15/8 mm Hg

27. In the splanchnic circulation,

A.   blood flow is regulated entirely by local factors independent of central control.

B.   venous drainage from the stomach flows directly into the ascending vena cava.

C.   more blood enters the liver from the venous drainage of other organs than from the hepatic artery.

D.   the hepatic portal vein carries blood from the liver to the pancreas, small intestine, and spleen.

E.   the total splanchnic blood flow accounts for < 10% of the CO.

28. When a person shifts from the supine to the standing position,

A.   arterial pressures in the legs and feet rise gradually over several minutes.

B.   vascular pressures in the rigid cranial vault are not affected.

C.   pressures in large vessels in the legs increase, but not in capillaries.

D.   over 1 or 2 minutes the volume of blood in pulmonary vessels decreases.

E.   valves in the veins prevent change in venous pressures.

29. If enough blood has been lost to cause a decrease in mean arterial pressure (MAP), which of the following would be true?

A.   Carotid sinus nerve activity would be increased.

B.   TPR would be decreased.

C.   Production of cAMP within cardiac myocytes would be increased.

D.   The arterioles of the intestine would be dilated.

E.   Heart rate would be decreased.

30. An untrained patient exercises on a treadmill at a moderate level. His control values are CO = 5 L/min, arterial pressure (systolic/diastolic) = 120/70 mm Hg, and heart rate = 70 beats/min. His exercise values are CO = 10 L/min, arterial pressure (systolic/diastolic) = 140/65 mm Hg, and heart rate = 120 beats/min. What is the main factor accounting for his increased CO?

A.   Increased heart rate

B.   Increased stroke volume

C.   Increased systolic pressure

D.   Increased pulse pressure

E.   Increased MAP

For Questions 31 and 32:
The following data are obtained during a catheterization procedure for a patient with diminished exercise tolerance:
Peak left ventricular pressure = 190 mm Hg
Mean left atrial pressure = 17 mm Hg
Peak aortic pressure = 110 mm Hg
Peak right ventricular pressure = 27 mm Hg
Peak pulmonary artery pressure = 23 mm Hg
Mean right atrial pressure = 6 mm Hg
CO = 3.2 L/min
Arterial O2 content = 19 mL/dL
Mixed venous O2 content = 15 mL/dL

31. What is the most likely cause of this patient’s diminished exercise tolerance?

A.   A decrease in the number of cardiac β receptors

B.   Inadequate pulmonary ventilation

C.   An elevation in left ventricular end-diastolic pressure

D.   Stenosis of the aortic valve

E.   Poor cardiac muscle function after a myocardial infarction (MI)

32. Which of the following interventions would be most likely to improve the overall status of this patient?

A.   Administration of an α-blocking agent

B.   Administration of a rapidly acting diuretic

C.   Administration of a β-blocking agent

D.   Administration of supplemental oxygen (O2)

E.   Replacement of the aortic valve

33. In severely anemic patients, a systolic ejection murmur can often be heard. Which of the following could account for this?

A.   Elevated heart rate

B.   Decreased velocity of blood flow

C.   Increased stroke volume

D.   Increased viscosity of blood

E.   Decreased blood density

34. Which of the following might be expected to occur in a patient suffering from moderate left ventricular heart failure?

A.   Increased cardiac ejection fraction

B.   Pulmonary edema

C.   Increased systemic arterial blood pressure

D.   Reduced central venous pressure

E.   Decreased end-diastolic volume

For Questions 35 and 36:
On a warm summer day, a 64-year-old retiree experiences a dull aching in the calf muscle of his right leg each time he takes a walk. After standing quietly, he can continue to go the same distance before the pain reappears. He reports that a week ago he had been digging postholes for a new fence, using his right foot. Upon testing, only small amounts of radiopaque contrast material pass from the femoral to the right popliteal artery in an arteriogram. During rest and a treadmill exercise tolerance test, the calf muscle blood flow was measured; resting flow in right leg was 2 mL/100 g/min; exercise right calf flow was 8 mL/100 g/min. The respective flows for the left calf muscle were 3 and 40 mL/100 g/min.

35. What is the probable cause of this patient’s problem?

A.   Myofascial pain due to overuse

B.   Spasm of small arteries

C.   Muscle cramps in the right calf

D.   Aneurysm in the right femoral artery

E.   Peripheral vascular disease of the right femoral artery

36. Why was the resting blood flow in the right calf muscle two-thirds of normal but the exercising flow only one-fifth of normal?

A.   Tissue injury limits exercise in the right leg.

B.   The obstruction becomes rate limiting when arterioles dilate with exercise.

C.   Local vasodilator metabolites are not produced in the right calf muscle.

D.   There is sympathetic vasoconstriction in the right leg.

E.   There is less activation of β2-adrenergic receptors by epinephrine in the right leg.

37. During administration of a drug that directly dilates systemic arterioles, you would expect

A.   reduced plasma renin concentration.

B.   elevated 24-hour urinary Na+.

C.   reduced plasma volume.

D.   reduced blood pressure.

E.   increased renal blood flow.

Answers and Explanations

1. E. Vagal tonic activity slows the heart at rest (p. 88). Therefore, cutting the vagus (parasympathetic efferent) nerve will cause a large increase in heart rate.

A With the influence of both systems removed, one cannot tell which one is responsible for the rise in heart rate.

B,C Cutting sympathetic supply to the heart or blocking adrenergic receptors has no effect or slightly slows the heart.

D Norepinephrine increases heart rate, but this action is independent of parasympathetic control.

2. C. Tonic vagus nerve activity slows the SA nodal rate of depolarization via activation of muscarinic receptors. Blocking cholinergic muscarinic receptors would increase heart rate (p. 88).

A Alpha-adrenergic blocking drugs would relax vascular smooth muscle but have little effect on heart rate.

B Beta-blockers such as propranolol reduce heart rate and the force of contraction.

D Cholinergic stimulating drugs such as carbachol decrease heart rate.

E Nitrovasodilator drugs relax vascular smooth muscle.

3. E. Phase 0 is the rapid rise of the ventricular action potential due to sodium entry (p. 89).

A Rapid filling occurs before the beginning of the action potential.

B The membrane is at rest during phase 4.

C Propagation through the Purkinje network occurs before the beginning of the action potential.

D Calcium release occurs during phase 2.

4. D. The ST segment is the interval from ventricular depolarization to ventricular repolarization (p. 92).

A The P wave is produced by atrial depolarization and occurs prior to the ventricular action potential.

B The PQ interval indicates the time from atrial to ventricular depolarization and occurs prior to the plateau.

C The Q wave is part of the QRS complex and occurs prior to the plateau.

E The T wave indicates ventricular repolarization and occurs when the plateau ends.

5. A. Inhibiting the Na+−K+ ATPase slows the removal of Ca2+ via Na+/Ca2+ antiport, thereby increasing the amount of Ca2+ available to signal contraction (p. 94).

B Catecholamines act by stimulation of cardiac β1-adrenergic receptors, which increase intracellular cAMP.

C The amount of Ca2+ available for contraction is increased.

D,E Cardiac glycosides do not affect cardiac β1-adrenergic receptors or muscarinic receptors.

6. C. CO is calculated either as the product of heart rate and stroke volume or as mean arterial pressure (MAP) divided by TPR. Heart rate can be calculated from the R wave-to-R wave interval, which is the time per beat, and stroke volume is the difference between end-systolic volume and end-diastolic volume (pp. 95106).

A,B The numbers do not yield stroke volume.

D,E The numbers do not yield MAP.

7. D. Demand for O2 is proportional to cardiac work, which is the product of stroke work (systolic pressure times stroke volume) times heart rate (pp. 9599).

A Work cannot be calculated without knowing aortic, or systolic, pressure.

B To calculate cardiac work, pressures by themselves provide insufficient information.

C To calculate cardiac work, you need to know stroke volume and systolic, not diastolic, pressure.

E Without knowing how often the heart contracts, there is insufficient information.

8. C. The patient’s tachycardia was due to the increased rate of depolarization of pacemaker cells in the SA node stimulated by the excess catecholamines epinephrine and norepinephrine. Epinephrine and norepinephrine also increase peripheral resistance by vasoconstriction and stimulate increased contractility, so blood pressure increases.

A Androgenic steroids build muscle mass with minimal cardiovascular effects.

B Parasympathetic activity slows the heart and may slightly decrease blood pressure.

D Aldosterone increases renal Na+ and water reabsorption, which raises blood pressure but reflexly decreases heart rate.

E Corticosteroids increase contractility and vasoconstriction by enhancing the effects of catecholamines but do not affect heart rate.

9. C. Norepinephrine increases cardiac contractility via cardiac β receptors (p. 96).

A It increases total peripheral resistance via vascular smooth muscle α1 receptors.

B Norepinephrine decreases venous compliance and therefore volume.

D The heart rate is directly increased by norepinephrine, not by reflex.

E Increased TPR and contractility increases afterload.

10. C. In the face of reduced coronary blood flow, the immediate goal is to reduce cardiac work, thereby reducing the demand for blood. Norepinephrine would stimulate cardiac contractility, increase cardiac work, and increase the demand for blood (p. 96).

A Nitrovasodilators dilate coronary arterioles.

B Beta-receptor antagonists reduce cardiac contractility.

D Supplemental O2 may help the patient through the acute stage.

E Calcium channel blockers reduce peripheral resistance and cardiac work.

11. C. The P wave results from atrial depolarization, which occurs immediately before atrial contraction (p. 99).

A The P wave occurs after the phase of rapid diastolic filling.

B Rapid systolic ejection occurs after the QRS complex.

D Atrial relaxation follows later.

E Ventricular contraction follows later.

12. E. Aortic pressure is greatest when ventricular pressure is also greatest (p. 98).

A Pressure continues to rise after the aortic valve opens.

B Pressure starts falling before the aortic valve closes.

C Rapid ventricular filling occurs later, after the mitral valve opens, when aortic pressure is falling.

D At the beginning of isovolumetric contraction, aortic pressure is close to its lowest value.

13. E. Diastole, when the mitral valve is open, lasts longer than systole, when the aortic valve is open (p. 99).

A Once the aortic valve closes, left ventricular pressure falls well below arterial pressure.

B When the mitral valve opens, the ventricle is still relaxing, and pressure continues to fall during the initial phase of filling.

C Typically, ~30% to 50% of the end-diastolic volume remains at the end of systole.

D To move blood from the atrium to the ventricle, ventricular pressure must be slightly less than atrial pressure during phase IV.

14. C. A congenital septal defect initially causes a left-to-right shunt which elevates pulmonary artery pressure by allowing blood at the higher pressure of the left heart into the right heart. Over time, this leads to scarring of small pulmonary vessels, poor oxygenation, and greatly increased vascular resistance. Eventually, pulmonary hypertension causes reversal of the shunt, now being right to left, which further reduces oxygenation of systemic arterial blood (p. 100).

A The hypertrophied right ventricle requires a higher filling pressure.

B With a right-to-left shunt, the left ventricular stroke volume is larger.

D The high vascular resistance leads to high pulmonary artery pressure.

E The blood flowing through the defect causes a systolic murmur.

15. B. The right heart struggles to pump returning blood, so central venous pressure increases, and peripheral veins become engorged.

A,E Pulmonary edema and an enlarged left atrium occur with left heart failure.

C Systemic arterial pressure is unchanged.

D Because both ventricles beat at the same rate, their stroke volumes must be equal.

16. B. Arterioles are the sites of highest resistance and therefore greatest pressure drop (pp. 101103).

A There is little drop in pressure until the arterioles are reached.

C Capillaries are individually very resistant, but their huge number in parallel reduces their combined resistance.

D,E Neither peripheral veins nor the inferior vena cava offer significant resistance to blood flow, so there is little pressure drop.

17. A. Stiff (low-compliance) arterial walls cause a large pulse pressure even with normal stroke volume (C) (p. 105).

B Common drug therapy such as β-blockers lowers heart rate.

D Cardiac hypertrophy results from the heart working against high afterloads.

E TPR is increased, but that has little effect on pulse pressure.

18. B. CO is inversely related to TPR so if CO increases, TPR decreases (p. 106).

A Most of the TPR is accounted for by arteriolar resistance (inverse of conductance). As the body grows, the CO is divided through more arterioles in parallel, which accounts for their overall conductance increase and not an increase in individual arteriolar conductance.

C The large-diameter aorta offers little resistance to flow.

D Heart rate declines as children grow, from over 120 beats per minute in infancy to a normal 70 in adulthood.

E Because CO must increase with body size, TPR must decrease.

19. A. Resistance is the pressure difference driving flow (MAP minus mean venous pressure) divided by flow (p. 102). MAP equals diastolic pressure plus one-third of pulse pressure, which is 70 + (130 – 70)/3 = 90 mm Hg (p. 106). Thus, the pressure difference is 90 – 10 = 80 mm Hg and resistance is 80 mm Hg ÷ 800 mL/min = 0.1 mm Hg/mL/min.

20. E. Alpha-adrenergic antagonists decrease sympathetic stimulation of arterioles and thereby reduce blood pressure (p. 106).

A If the kidneys retain salt, then the extracellular compartment expands and raises blood pressure.

B It is renin, rather than angiotensinogen availability, that determines the production of angiotensin II. However, angiotensin II raises blood pressure.

C Acetylcholine slows the heart, but it is not given IV, as it is hydro-lyzed by circulating esterases.

D Blocking adenosine receptors decreases coronary blood flow, which compromises cardiac function.

21. B. Dilation causes decreased peripheral resistance and decreased blood pressure, causing the baroreceptor reflex to increase heart rate (p. 107).

A The drop in arterial pressure decreases carotid sinus nerve activity.

C Arterial blood volume does not change.

D Sympathetic activity to the splanchnic region also increases.

E Venous pressure increases via reflex vasoconstriction.

22. C. In the face of decreased extracellular fluid volume, the renin concentration increases (p. 109).

A Aldosterone also increases.

B Carotid sinus nerves fire more slowly because blood pressure is reduced.

D Vasopressin (ADH) is also increased.

E Peripheral vasoconstriction would reduce the net filtration pressure.

23. C. Distention of the low-pressure mechanoreceptors located at the venoatrial junctions reduces sympathetic stimulation of the kidneys and causes the release of ANP. Both actions relax renal arterioles and permit increased glomerular filtration (p. 109).

A Atrial natriuretic peptide (ANP) release would be increased

B ANP and reduced sympathetic drive inhibit renin secretion.

D The afferent neurons from the baroreceptors inhibit central stimulation of large veins.

E There would be no direct influence on coronary vessels.

24. D. Low plasma oncotic pressure increases the net filtration pressure by reducing the force opposing capillary hydrostatic pressure (p. 111).

A Arteriolar vasoconstriction reduces capillary pressure and reduces filtration.

B Filtration is greater at the arteriolar end of the capillary, where pressure is higher.

C Venodilation reduces mean capillary hydrostatic pressure.

E Dehydration tends to concentrate plasma proteins, raising oncotic pressure, and leads to reflex arteriolar vasoconstriction. Both effects reduce or even reverse net filtration pressure.

25. C. Decreased albumin concentration decreases plasma oncotic pressure, resulting in less reabsorption and more fluid (edema) in the interstitial space (p. 112).

A Decreased capillary pressure produces less filtration and less interstitial fluid.

B Contraction of precapillary sphincters decreases capillary pressure.

D Increased interstitial hydrostatic pressure can result from edema, but it is not a cause of edema.

E Decreased venous pressure decreases capillary pressure.

26. A. The systolic pressure in the right ventricle is virtually the same as the systolic pulmonary arterial pressure.

B–E Right ventricular diastolic pressure is virtually the same as central venous pressure, which is typically about 2 mm Hg.

27. C. The majority of hepatic blood is drainage from the stomach, spleen, pancreas, and intestines (p. 115).

A Splanchnic blood flow is severely decreased by central control during exercise and dehydration.

B Venous blood from the stomach flows via the portal vein to the liver.

D Portal blood flows into the liver.

E At rest, splanchnic blood flow is?25% of the CO.

28. D. Over the course of a minute or so, up to 500 mL of blood shifts from the pulmonary circuit to the abdomen and lower extremities (p. 116).

A Pressures in the arterial system are affected immediately.

B The rigidity of the cranium does not prevent a fall in both arterial and venous pressures.

C Capillary pressures in the legs gradually rise, as they can never be less than venous pressure.

E Valves prevent backflow, but as blood accumulates in the lower extremities, venous pressure rises if the person remains stationary.

29. C. The fall in arterial pressure would trigger reflex adrenergic stimulation of the heart via β1 receptors, which would lead to the production of cAMP (p. 117).

A Low blood pressure causes decreased carotid sinus nerve activity.

B,D Reflex sympathetic activation would cause peripheral vasoconstriction, including vessels in the gastrointestinal (GI) tract.

E Sympathetic stimulation of the heart would increase heart rate.

30. A. The CO doubled and heart rate almost doubled; thus, increased heart rate accounts for most of the change in CO (p. 117).

B A small increase in stroke volume accounts for the rest.

C–E Increased systolic and pulse pressure with little change in diastolic pressure is typical of exercise, but pressure changes by themselves do not change CO.

31. D. The large difference between peak left ventricular pressure and peak aortic pressure indicates stenosis of the aortic valve. This prevents adequate amounts of blood from being pumped out of the left ventricle into the aorta.

A,E A decrease in the number of β receptors or poor cardiac muscle function would decrease cardiac contractility, and the left ventricle would be unable to generate pressures of 190 mm Hg.

B Pulmonary ventilation is adequate, as arterial blood is well oxygenated.

C The diminished ejection causes a backup of blood, elevating left ventricular diastolic and left atrial pressures. High diastolic pressures are a result, not a cause, of the inability of the left ventricle to eject blood during systole.

32. E. The stenosed aortic valve needs replacement.

A,B Administration of an α-blocking agent or a rapidly acting diuretic would reduce the systemic arterial pressure, which might further impair the cardiovascular status of the patient.

C A β-receptor blocker would reduce cardiac contractility and reduce the CO.

D Blood oxygenation is adequate in this patient and does not need to be supplemented.

33. C. To maintain adequate delivery of O2 in severe anemia, the body responds with an increased heart rate and high stroke volume. The high blood velocity caused by the high stroke volume leads to turbulence, which is the source of the murmur (B).

A The high heart rate by itself does not cause increased ejection velocity.

D Decreased hematocrit results in decreased viscosity, which is another cause of turbulence.

E Low density decreases the likelihood of turbulence.

34. B. Left heart failure, because of a high end-systolic volume, increases left atrial pressure. This raises pulmonary capillary pressure and produces pulmonary edema.

A The cardiac ejection fraction is reduced in the failing heart.

C With moderate heart failure, there is no consistent change in arterial blood pressure.

D Heart failure is characterized by fluid retention, which increases central venous pressure.

E End-diastolic volume increases due to the large volume remaining after systole and the high left atrial pressure.

35. E. Atherosclerosis in the right femoral artery restricts blood flow.

A The test results indicate a blood flow problem rather than a muscle tissue problem.

B Spasm of small arteries of the fingers and toes may occur in Raynaud disease in response to exposure to cold. Anything that stimulates the sympathetic nervous system can cause arterial spasms.

C Muscle cramps can limit blood flow, but they are relieved by stretching the muscle and do not come and go with exercise and rest.

D An aneurysm (a bulge in the artery wall) would not limit blood flow.

36. B. At rest, the arterioles are mostly constricted and present greater overall resistance than the affected femoral artery. As the arterioles dilate from locally-produced metabolites with exercise, the obstruction somewhat limits flow in the right leg, while flow in the unobstructed leg increases greatly.

A The right leg still exercises until pain from the hypoxia in muscles stops it.

C Vasodilator metabolites are still produced with exercise, causing a 4-fold increase in blood flow.

D,E In exercising muscle, local control overrides neurohumoral control, and the neural innervation of the right calf is normal.

37. D. Arteriolar vasodilation reduces systemic blood pressure.

A,B The lower pressure reduces filtered Na+, and the kidney reflexly retains Na+, so urine Na+ is lower, and renin rises.

C Plasma volume rises from Na+ retention.

E Lower blood pressure slightly reduces renal blood flow in the range of autoregulation.