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Although most of the placental blood passes through the liver, a fraction of theplacental circulation passes directly into the vena cavathrough the ductus venosus.Foramen ovale, a “right-to-left” shunt through whichmost of the blood from the inferior vena cava flows intothe left atrium, bypassing the right heart and the pulmonary circulation.Ductus arteriosus, another right-to-left shunt betweenthe pulmonary artery and the aorta. Pulmonary vascularresistance is high in the fetus, due to the collapsed stateof the lungs and low oxygen tension in the lungs; 90%of pulmonary arterial blood flows through the ductusarteriosus to the aorta.These structures all normally close shortly after birth, althoughanatomical closure, as opposed to functional closure, requires141Unlike the adult, the fetal circulation can be considereda parallel circulation.
Much of the right ventricularoutput is shunted past the lungs to the aorta through the ductusarteriosus, mixing with blood ejected by the left ventricle. Flowthrough the pulmonary circulation is not critical, since oxygenation of blood does not take place in the lungs in utero. Withclosure of the foramen ovale and ductus arteriosus shortlyafter birth, the fetal circulation is transformed to a seriescirculation.more time. Inflation of the lungs and inhalation of oxygenrich air reduces pulmonary vascular resistance, reversing flowthrough the ductus arteriosus.
High oxygen tension initiatesclosure of the ductus. With increased venous return from thelungs to the left atrium and reduced flow to the right atriumdue to occlusion of the placental circulation, left atrial pressure rises above right atrial pressure, closing a valve over theforamen ovale. With closure of the ductus arteriosus andforamen ovale, the “adult” pattern of circulation of bloodthrough the right heart, lungs, left heart, and systemic circulation is established.142Cardiovascular PhysiologyReview QuestionsCHAPTER 8: OVERVIEW OF THE HEARTAND CIRCULATION1.
The greatest volume of blood is found in the:A.B.C.D.E.systemic arteries.systemic veins.pulmonary arteries.pulmonary veins.chambers of the heart.2. Contraction of which chamber of the heart is best describedas a constriction of the chamber resulting in shortening frombase to apex?A.B.C.D.E.Left atriumRight atriumLeft ventricleRight ventricleAll of the above3. Of the following parts of the circulation, which receivesthe smallest blood flow (as a percentage of cardiac output) atrest?A.B.C.D.E.Coronary circulationLiver and gastrointestinal tractSkeletal muscleKidneysCerebral circulationCHAPTER 9: CARDIAC ELECTROPHYSIOLOGY4.
Rapid phase 3 repolarization of cardiac myocytes duringthe action potential is mainly associated with:A. opening of Na+ channels.B. reduced conductance of the inwardly rectified K+ current(iK1).C. opening of voltage-sensitive slow L-type Ca2+ channels.D. inactivation of Na+ channels.E. activation of K+ channels.6. Conduction velocity is slowest in the:A.B.C.D.E.atrial myocytes.AV node.bundle of His.Purkinje fibers.ventricular myocytes.CHAPTER 10: FLOW, PRESSURE,AND RESISTANCE7. Given a resting heart rate of 75 and arterial blood pressureof 130/80 mm Hg, what is the approximate mean arterialpressure (MAP)?A.B.C.D.E.90 mm Hg97 mm Hg105 mm Hg110 mm Hg115 mm Hg8.
The highest pulse pressure in the circulation is observedin the:A.B.C.D.E.left ventricle.right ventricle.aorta.pulmonary artery.systemic arterioles.9. Which of the following changes would result in the greatestincrease in flow through a tube, assuming that other factorsare held constant?A. Doubling of the pressure gradient between ends of thetubeB.
Reducing the viscosity of the fluid by halfC. Doubling the viscosity of the fluidD. Reducing the length of the tube by halfE. Doubling the radius of the tube5. The electrocardiogram may reveal:10. Which of the following conditions favors laminar flow ina tube?A.B.C.D.E.A.B.C.D.E.abnormalities in cardiac rhythm and conduction.location and extent of myocardial ischemia.orientation of the heart and size of chambers.effects of abnormal electrolyte levels.All of the above.Wide tube diameterRapid velocity of fluid flowHigh viscosity of fluidHigh density of fluidPulsatility of flowReview Questions11.
Wall tension in a blood vessel would be increased by:A. reduction of vessel radius.B. reduction of hydrostatic pressure within the vessellumen.C. reduction of hydrostatic pressure in the interstitialspace.D. reduction of transmural pressure.E. None of the above.CHAPTER 11: THE CARDIAC PUMP12. The beginning of the isovolumetric contraction periodfor the right ventricle is marked by:A.B.C.D.E.closure of the aortic valve.closure of the pulmonic valve.closure of the mitral valve.closure of the tricuspid valve.opening of the mitral valve.13. The correct order of valve opening and closure during acardiac cycle is:A.
mitral closure, tricuspid closure, pulmonic opening, aorticopening, aortic closure, pulmonic closure, tricuspidopening, mitral opening.B. tricuspid closure, mitral closure, pulmonic opening, aorticopening, aortic closure, pulmonic closure, tricuspidopening, mitral opening.C. mitral closure, tricuspid closure, aortic opening, pulmonicopening, aortic closure, pulmonic closure, tricuspidopening, mitral opening.D. mitral closure, tricuspid closure, pulmonic opening, aorticopening, pulmonic closure, aortic closure, tricuspidopening, mitral opening.E.
mitral closure, tricuspid closure, pulmonic opening, aorticopening, aortic closure, pulmonic closure, mitral opening,tricuspid opening.14316. An increase in myocardial contractility will result in whichof the following changes in the force–velocity relationship?A.
An increase in the maximum force of contraction withoutchange in VmB. An increase in the maximum force of contraction and anincrease in VmC. A decrease in the maximum force of contraction withoutchange in VmD. A decrease in the maximum force of contraction and anincrease in VmE. A decrease in the maximum force of contraction and adecrease in Vm17. When the vascular function curve and cardiac functioncurves are plotted on the same graph, the point of intersectionrepresents the:A.B.C.D.E.point at which baroreceptor activation occurs.resting cardiac output and central venous pressure.normal mean circulatory pressure.normal mean arterial pressure.point of maximum contractility.CHAPTER 12: THE PERIPHERAL CIRCULATION18.
Release of nitric oxide by the endothelial cells in a smallartery would be expected to produce all of the followingeffects except:A. elevation of cGMP in smooth muscle underlying theendothelium.B. inhibition of platelet adhesion to the vascular wall.C. elevation of free intracellular Ca2+ in the underlyingsmooth muscle.D. vasodilation of the vessel.E. increased hydrostatic pressure in downstream capillaries.14. In respiratory sinus arrhythmia, the increase in heart rateduring inspiration is initiated by:19. In an experimental model, the perfusion pressure for anartery is increased. A rise in blood flow through the artery isobserved, but despite continued high perfusion pressure, flowfalls over a 2-minute period toward the baseline level.
Thisreduction in flow is most likely the result of:A.B.C.D.E.A.B.C.D.E.reduced stretch of arterial baroreceptors.increased stretch of arterial baroreceptors.release of atrial natriuretic peptide.reduced stretch of atrial stretch receptors.increased stretch of atrial stretch receptors.autoregulation of blood flow.reactive hyperemia.active hyperemia.shear stress–induced nitric oxide release.increased sympathetic nerve activity.15. Activation of the sympathetic nervous system willproduce:20. Vasodilation is evoked by binding of adrenergic transmitter by which type of vascular adrenergic receptor?A.B.C.D.E.A.B.C.D.E.increased heart rate.arterial vasoconstriction.constriction of veins.increased myocardial contractility.All of the above.α1α2β1β2All of the above144Cardiovascular Physiology21.
Afferent nerve activity from the arterial baroreceptors willbe greatest when:A.B.C.D.E.MAP and pulse pressure are both high.MAP is high and pulse pressure is low.MAP and pulse pressure are both low.MAP is low and pulse pressure is high.MAP and pulse pressure are in the normal resting range.22. Left coronary artery blood flow is highest during:A.B.C.D.E.early systole.late systole.early diastole.mid diastole.late diastole.Section4RESPIRATORYPHYSIOLOGYThe components of the respiratory system are the lungs, airways, and themuscles of breathing. The primary function of this system is to facilitate theexchange of oxygen and carbon dioxide between the body and theenvironment.
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