1 Quiz 10 Results Name Quiz 10a Attempt Score 1.2234 Attempts 141 (Total of 144 attempts for this assessment) Question 1: Multiple Choice Average Score 0.40426 points If an arteriole were to constrict to one-fourth of its previous radius, and blood pressure remained the same, then flow through the arteriole would… Correct Percent Answered decrease by a factor of 4. 5.674% decrease by a factor of 16. 9.929% decrease by a factor of 64. 2.128% decrease by a factor of 256. 80.142% decrease, to an extent that cannot be determined from the data given. 2.128% Unanswered 0% Question 2: Multiple Choice Average Score 0.42199 points In which one of the following situations would the end systolic volume be the greatest? Correct Percent Answered when stroke volume is increased 7.092% when the force of myocardial contraction is increased 7.092% when parasympathetic stimulation of the heart is increased 84.397% when the intracellular store of calcium in cardiac myocytes is increased 1.418% Unanswered 0% Question 3: Multiple Choice Average Score 0.39716 points Which one of the following best explains why hyperkalemia can cause bradycardia? Correct Percent Answered Hyperkalemia causes a negative shift in the K+ equilibrium potential. 7.801% Hyperkalemia reduces the driving force for outward K+ current. 79.433% Hyperkalemia increases the frequency of action potentials in sympathetic nerves to the heart. 2.128% Hyperkalemia hyperpolarizes the cardiac muscle membrane, which reduces inactivation of Na+ channels. 10.638% Unanswered 0% Question 4: Essay Average Score 0 points2 A baby was born in obvious respiratory distress, gasping for breath and showing cyanosis (blue skin due to poorly oxygenated blood). This continued for days with no sign of improvement. Initial imaging studies revealed that the heart was structured as shown in the attached diagram (Congenital Heart Defect.jpg). Answer the following 3 questions: What is wrong with the heart structure shown in the left diagram? The neonatal cardiologist was astounded that the baby could survive at all. Based on the structure shown in the left diagram, she would have expected the baby to die within minutes of birth. Briefly explain why the cardiologist would have expected the baby to die so quickly. c. Upon closer examination of the images, the cardiologist realized that her initial assessment of heart structure was wrong. As shown in the right diagram, there was also a ventricular septal defect (VSD, a hole in the septum between the ventricles). In addition, there was a patent (open) ductus arteriosus (PDA, not shown in the diagrams) connecting the pulmonary artery to the aorta. Flashing back to her undergraduate physiology class, she realized why the baby did not die immediately. Briefly explain how these two additional birth defects (VSD & PDA) would allow the baby to live, at least for a while. Given Answers The left and right ventricle are completely walled off. Blood coming from Blood coming into the right side of the heart goes directly to the rest of the body rather than the lungs first to be oxygenated. The baby, lacking a continuous source of oxygen, could not have been expected to live long. c. Oxygenated blood would be allowed to mix with deoxygenated blood. There would be at least a dilute source of oxygen circulating throughout the body but this would be insufficient in the long run to sustain life. Deoxygenated blood (from the rest of the body) enters the heart through the superior & inferior vena cava, moving into the right atrium, and then into the right ventricle, where it proceeds to exit the heart to re-enter cirulation to the rest of the body. However, having never been pumped to the lungs (through the pulmonary artery as it should have), this blood remains deoxygenated and cannot provide sufficient oxygen to those body tissues as it is recirculated continuously without proper reoxygenation. As this blood continuously moves from the body tissues to the heart only to return to the body tissues again without oxygenation, the blood continues to be further depleted of oxygen until it cannot provide any units of oxygen to the tissues and these body tissues are forced to undergo anaerobic respiration as their primary source of ATP production. Alternatively, oxygenated blood from the lungs enters the pulmonary veins, moves into the left atrium, enters the left ventricle, and exits the heart through the pulmonary artery, where it re-enters the lungs for further oxygenation. This oxygenated blood, however, serves little purpose as it fails to be pumped to the peripheral body tissues which require oxygenation for efficient ATP production. Because this heart has blood pumping on two different circuits entirely (one circuit is pumping blood exclusively from the peripheral tissues of the body to the heart and back to the peripheral tissues; the other circuit involves the pumping of blood from the heart to the lungs and back to the heart), the peripheral tissues of the body would quickly become severely oxygen-deprived as the blood circling from the body to heart and back to the body failed to be properly pumped through the lungs for oxygenation. Therefore, within seconds, the peripheral body tissues would soon3 become oxygen-deprived. The primary and most immediate concern would be the lack of oxygen able to reach the brain. c) The VSD allows for the mixing of oxygenated and deoxygenated blood from the right and left ventricles; this allows for some oxygenated blood to enter general body circulation through the PDA (which would not be possible without the PDA). This also allows for some deoxygenated blood from the right ventricle to enter the lungs through the PDA (which was not possible before). Although this is not an incredibly efficient system as some of the blood entering the lung is already oxygenated (as it just entered the heart from the pulmonary vein and exited the heart through the pulmonary artery only to re-enter the lungs) this does allow for some dexygenated blood (from the right ventricle) to enter the lungs (which was not possible before); therefore, more dexoygenated blood is now being reoxygenated (after which it may be pumped throughout the peripheral body tissues to provide them with oxygen for cellular respiration). The aorta projects from the left ventricle rather than the right. The pulmonary artery projects from the right