PEX-05-06

Exercise 5: Cardiovascular Dynamics: Activity 6: Studying S tudying the Effect of Stroke Volume on Pump Activity Lab Report Pre-lab Quiz Results You scored 100% by answering 5 out of 5 questions correctly. 1. Which of the following variables directly contributes to to preload? You correctly answered: b. venous return 2. Which of the following would not  increase  increase end diastolic volume? You correctly answered: c. dehydration 3. Increased contractility contractility of the heart results in all but which of the the following? You correctly answered: d. increased end systolic volume 4. Which of the following does not  affect  affect stroke volume? You correctly answered: d. All of these affect stroke volume. 5. Which of the following is not  equivalent  equivalent to the others? You correctly answered: c. end diastolic volume

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Experiment Results Predict Question: Predict Question: If the pump rate is analogous to the heart rate, what do you think will happen to the rate when you increase the stroke volume? Your answer : a. The pump rate will decrease to maintain cardiac output. Stop & Think Questions: Why did changing the ending pump volume (ESV) automatically change the stroke volume? You correctly answered: d. The heart intrinsically alters stroke volume to accommodate changes in preload. The flow has stayed constant with each trial because You correctly answered: a. cardiac output is equivalent to blood flow. How does the heart provide for an increase in stroke volume? You correctly answered: b. by increasing contractility Experiment Data: Flow (ml/min) 5086.8 5086.8 5086.8 5086.8 5086.8 5086.8 5086.8 5086.8

Rad. L (mm) 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0

Rad. R (mm) 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0

Str. V (ml) 10 20 30 40 50 60 80 100

Rate (strokes/min) 508.7 254.3 169.6 127.2 101.7 84.8 63.6 50.8

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Press. L (mm Hg) 40 40 40 40 40 40 40 40

Press. Dif. R (mm Hg) 40 40 40 40 40 40 40 40

Post-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1. What do you think would happen when stroke volume is decreased? You correctly answered: b. Pump rate would increase. 2. Why might an athlete's resting heart rate be lower than that of the average person? You correctly answered: e. Stroke volume and contractility have increased. 3. In this activity, which of the following stayed constant? You correctly answered: c. flow rate 4. Which of the following is true? You correctly answered: d. ESV = EDV - SV

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Review Sheet Results 1. Describe the Frank-Starling law in the heart. Your answer: The greater the stretch of the cardiac muscle cell, the greater the force of contraction. 2. Explain what happened to the pump rate when you increased the stroke volume? Why do you think this occurred? How well did the results compare with your prediction? Your answer:  As the stroke volume is increased, it takes longer to fill the pump and the pump rate slows. To maintain adequate blood flow to tissues, the stroke volume must be greater if the heart rate is lowered. If the rate remains constant, increasing the stroke volume causes cardiac output to increase.

3. Describe how the heart alters stroke volume. Your answer: By changing contractility which in turn increases stroke volume 4. Describe the intrinsic factors that control stroke volume. Your answer:  The intrinsic factors that determine stroke volume are preload and contractibility. The preload gives the volume of blood that the ventricle has available to pump, as well as the end diastolic length of the muscle. The contractility is the force that the muscle can create at the given length. These factors establish the volume of blood pumped with each heart beat Aracely Perez Bridgitte Luna Kristal Barrientos Sonia L. Gonzales Fernando Marquez

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