RT Book, Section A1 Mohrman, David E. A1 Heller, Lois Jane SR Print(0) ID 1153947123 T1 Answers to Study Questions T2 Cardiovascular Physiology, 9e YR 2018 FD 2018 PB McGraw-Hill Education PP New York, NY SN 9781260026115 LK accesscardiology.mhmedical.com/content.aspx?aid=1153947123 RD 2023/12/04 AB 1–1. The lungs always receive more blood flow than any other organ because 100% of the cardiac output always passes through the lungs.1–2. False. Flow through any vascular bed depends on its resistance to flow and the arterial pressure. As long as this pressure is maintained constant (a critical point that is dependent on adjustments in cardiac output), alterations in flow through any individual bed will have no influence on flow through other beds in parallel with it.1–3. A leaky aortic valve will cause a diastolic murmur. Normally, the aortic valve is closed during diastole when there is a large reverse pressure difference between the aorta and left ventricle.1–4. False. Slowing conduction through the AV node will have no effect on the heart rate but will increase the interval between atrial and ventricular excitation. The heart rate is normally slowed by decreases in the rate of action potential initiation by pacemaker cells in the SA node.1–5.Saying that the diameter of a vessel increases by 10% is equivalent to saying that its radius increases by 10%; that is, the radius after the change is 1.1 times the radius before the change. The Poiseuille equation says that, other factors equal, resistance is proportional to 1 over radius to the fourth power: R∝1/r4 Thus, Rbefore∝1/(rbefore)4Rafter∝1/(1.1rbefore)4=[1/(1.1)4][1/(rbefore)4]=(1/1.46)Rbefore=0.68Rbefore Therefore, a 10% increase in vessel radius will reduce its resistance by 32%.Because Q·=ΔP/R, and Rafter = 0.68 RbeforeQ·after=ΔP/0.68Rbefore … and for a given ΔP … Q·after=1/0.68Rbefore=1.46Q·before Therefore, for a given ΔP, a 10% increase in vessel diameter will increase flow by 46%.[Note: One must always use change factors NOT percentage changes in these equations.]1–6.Wrong! The pulmonary and systemic circuits are arranged in series and therefore must have the same output flow in the steady state.Wrong! The right and left hearts are served by a common electrical excitation system and therefore beat at the same rate.Wrong! Although it is true that the right ventricle is less muscular than the left, that fact does not explain why pulmonary pressure is so low. Actually, it is the other way around because pulmonary arterial pressure is low, the right ventricle does not have to be very muscular to pump blood into the lungs.Right! ΔP=Q⋅×R. Because Q⋅ is the same (= CO) through the lungs and the systemic circulation, the only way pulmonary arterial pressure could be relatively low is for pulmonary vascular resistance to be relatively low.Wrong! CO = HR × SV. CO and HR are the same for both the right and left pumps. Therefore, the SV of the right ventricle must be equal to that of the left.This is a complete cop-out for a reasoned explanation!1–7. Significant blood loss has a profound negative effect on cardiac pumping because there is not enough blood left to fill the heart properly. This results in decreased cardiac output because of the Starling law of the heart. The consequence of decreased cardiac pumping ability is a lessened pressure difference between arteries and veins. Because of the basic flow equation, less ΔP causes less flow through ...