Assignment 2

1 .		In this exercise you will study the effects of a change in heart rate on other parameters of the cardiovascular system. Before you run your experiment, answer the following questions below. What effect will a change in heart rate have on each of the (five) other parameters indicated in the Variables view? Imagine that you have just walked into your biology class and your instructor has surprised you with a rather lengthy, unannounced essay exam on the cardiovascular system. Your heart rate increases in response to this stress. How will this increase in heart rate affect other parameters of the cardiovascular system such as blood pressure, stroke volume, and total peripheral resistance? Which of these other parameters will change in an effort to maintain blood pressure homeostasis? How will each parameter change? What role will the nervous system play in homeostasis?
2 .		Click on the Start button and allow normal recordings to continue for 5 seconds. After 5 seconds, click and hold on the slider for heart rate and increase heart rate to close to the maximum value for this slider. Click on the box next to this slider to freeze heart rate at this value. Notice that you have increased heart rate. Look at the slider bars for vessel radius, blood viscosity, systolic ventricle volume, blood volume, and venous capacity. Observe what is happening to each of these parameters. Which parameters changed and how did each parameter change? For example, what happened to vessel radius? Did vessel radius increase or decrease? Why? Do these results make sense to you?
3 .		Did any parameter(s) remain unchanged? If so, which one(s)? Do these results make sense to you? Explain your answers and relate them to understanding of blood pressure homeostasis to explain why each parameter did or did not change in response to an increase in heart rate.
4 .		Stop the stimulation and repeat this experiment. This time, look at the Nerve Impulse tracings and take note of any changes that you see. What happened to the electrical activity of each set of nerves? Which nerves showed an increase in electrical activity? Which showed a decrease? Did electrical activity stay the same for any of these nerves? Explain your answers.
5 .		Repeat the steps described in exercise 2; however, this time instead of changing heart rate, increase blood viscosity. Then answer the following questions: Which variables changed to compensate for the increase in blood viscosity? Based on what you know about cardiovascular relationships and hemodynamics, do these changes make sense to you? Why or why not? Explain what you observed.
6 .		Did MAP return to normal? Why or why not? Explain your answers.
7 .		Repeat this process to study a decrease in blood viscosity and describe your answers below.