1 Quiz 11 Results Name Quiz 11a Attempt Score 0.86364 Attempts 143 (Total of 144 attempts for this assessment) Question 1: Multiple Choice Average Score 0.3951 points One of the long-term consequences of rheumatic fever is mitral stenosis, a narrowing of the opening of the mitral valve of the heart (left atrioventricular valve). Which one of the following conditions would you least expect in a patient with mitral stenosis? Correct Percent Answered higher pressure in the left atrium than the left ventricle during diastole 8.392% smaller end-diastolic volume in the left ventricle 4.196% low blood pressure in the pulmonary circulation 79.021% reduced cardiac output 2.098% tachycardia 6.294% Unanswered 0% Question 2: Multiple Choice Average Score 0.12937 points Given that acetylcholine has a negative inotropic (should read “chromotropic”) effect on cardiac muscle, how would parasympathetic stimulation affect end systolic volume (ESV)? Correct Percent Answered Parasympathetic stimulation would decrease ESV. 25.874% Parasympathetic stimulation would increase ESV. 55.944% Parasympathetic stimulation would not affect ESV. 18.182% Don’t choose this one! 0% Unanswered 0% Question 3: Multiple Choice Average Score 0.33916 points At the arteriolar end of a particular capillary, blood pressure is 30 mm Hg, hydrostatic pressure in the surrounding interstitial space is -2 mm Hg, the osmotic pressure exerted by plasma proteins is 25 mm Hg, and the osmotic pressure exerted by interstitial proteins is 2 mm Hg. What is the direction of fluid movement across the capillary wall, and the net driving force? Correct Percent Answered absorption, 5 mm Hg 2.797% absorption, 7 mm Hg 6.294% absorption, 9 mm Hg 3.497% filtration, 5 mm Hg 13.287% filtration, 7 mm Hg 6.294% filtration, 9 mm Hg 67.832%2 Unanswered 0% Question 4: Essay Average Score 0 points On a snowboarding trip to Mammoth Mountain over Winter Break, a Swedish friend tried to convince you of the health benefits of prolonged sweating in a hot sauna followed immediately by immersion in an ice-cold lake. As a future physiology student, it occurred to you that in the hot sauna, your cutaneous blood vessels will be dilated to radiate body heat. However, when you plunge into the cold lake, those same cutaneous vessels will rapidly constrict to conserve body heat. With some concern, you realized that peripheral vascular resistance will therefore be low in the sauna, and then abruptly become high in the lake. You wondered whether your heart can maintain adequate cardiac output in the face of such a change in peripheral resistance. Despite your misgivings, you tried the sauna/lake combination and you survived. Assuming that the procedure is quite safe (the heart can compensate), and that cardiac output from the right heart does not change, answer the following questions: What will be the immediate effect of this increase in peripheral resistance on cardiac output from the left side of the heart? Briefly explain your answer. What intrinsic mechanism(s) (originating within the heart) could compensate for the change in cardiac output described in part a? Briefly explain how the mechanism(s) work. c) What extrinsic mechanism(s) (originating outside the heart) could compensate for the change in cardiac output described in part a? Briefly explain how the mechanism(s) work. Given Answers The immediate effect of an increase in peripheral resistance would be a drop in cardiac output, because the mean arterial pressure is proportional to cardiac output and peripheral resistance. As cardiac output is decreased, mean arterial pressure would also drop, triggering baroreceptors. Baroreceptors would trigger an increase in heart rate which would in turn increase both mean arterial pressure and cardiac output. c) Vessels would also be affected, and would constricted in response to the reduced amount of blood circulating. This would help to maintain mean arterial pressure, which would combat the effects of a reduced cardiac output. The peripheral resistance on cardiac output from the left side of the heart will decrease because left ventricular pressure will not have enough time to change. The amount of blood that fills in the right atrium after being oxygenated in the lungs is not affected by the left decrease, which means that the blood pumped to the body remains the same. c) The direct hot to cold experience will initiate a sympathetic response, releasing norepineprhine, which will make the heart pump more forcefully. Increase in peripheral resistance leads to decreased cardiac output form left side to maintain constant mean arterial pressure. This will result in decreased contractions and lesser forceful contractions and slower heart rate and lower stroke volume. Phospholambdin would not be phosphorylated which means it will inhibit the calcium pump in the sarcoplasmic reticulum and prevent the uptake and release of calcium resulting in decreased contractions, and less forceful contractions as well as resulting in decreased stroke volume all ultimately leading to lower cardiac output. c) Parasympathetic stimulation would also decrease heart rate and stroke volume but does not have an effect on forcefullness of contractions. Parasympathetic nerve stimulation results in release of acetylcholine which results in the stimulation of GIRK channels which leads to outward potassium current. The already at negative potential and inwardly rectifying channels are opened and increased potassium current at negativ currents slows down the packemaker potential. The result of decreased inward current that is still depolarizing decreases the slope of the pacemaker potential which makes reaching threshold harder and so the threshold is reached later and the frequency of reaching threshold goes down, ultimately decreasing3 heart rate and decreasing cardiac output. The immediate effect will decrease left cardiac output becasue the left ventricular pressure did not have time to change so the low pressure paired with the increase in peripheral resistance will cause a decrease in cardiac output. Since the cardiac output on the right does not change, the left ventricles will have a greater volume at the end of diastole and the increase in volume will increase the force of contraction. This is shown with Starling's law. The increase in left ventricular systolic pressure will compensate for increased