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Axia College Material
Appendix K
CardioLab
Before beginning CardioLab:
1. Print out these lab experiment instructions. A printed copy of these instructions will aid in
completing the lab accurately and effectively, because you will not need to switch back
and forth between computer screens.
2. Disable your pop-up blocker. CardioLab and the CardioLab online notebook will open in
new browser windows. If you have a pop-up blocker, they will be blocked.
3. Read the online introduction and background information related to this lab
The experiment is divided into two sections: Self-Check Experiment and Exploration Experiment.
The Self-Check Experiment is designed to help you become familiar with the lab. The answers to
the Self-Check Experiment questions are given to you (in red text). Completing the Self-Check
Experiment and checking your answers will help you verify that you are completing the
experiments correctly.
The Exploration Experiment is the experiment you will be conducting and turning in to your
instructor for credit. You will report your findings for the Exploration Experiment in the CardioLab
report.
Getting to Know CardioLab
The following information is designed to help you become familiar with the operation of
CardioLab.
The first screen that appears in CardioLab presents the relationship between resistance, cardiac
output (CO), and mean arterial pressure (MAP). This feature of CardioLab is known as the
"Equation." It is essential that you understand the relationships of these factors before beginning
an experiment. The Equation feature is designed to help you do this.
Follow the exercises below to examine the effects of resistance and cardiac output on MAP.
These exercises are an excellent way to reinforce your understanding of important relationships
that influence MAP. You can manipulate any of the parameters in this view and watch how your
change influences MAP.
This feature is not designed to demonstrate homeostasis; therefore, you will not see these
parameters change to return MAP to normal. Homeostasis will be investigated in the other
assignments.
Self-Check Experiment: Factors That Affect Cardiac Output and
Mean Arterial Pressure
Effect of Blood Viscosity on Mean Arterial Blood Pressure
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A number of different conditions can influence blood viscosity. For example, blood viscosity will
decrease due to a decrease in the number of red blood cells in the condition known as anemia.
Conversely, individuals living at higher altitudes often experience polycythemia-an abnormal
increase in red blood cell count. Polycythemia occurs in response to reduced oxygen content of
the atmosphere at higher altitudes. Both decreases and increases in blood viscosity strongly
influence MAP.
1. Develop a hypothesis to predict the effect of an increase in blood viscosity on blood pressure.
Then, test your hypothesis as follows:
You should hypothesize that an increase in blood viscosity will produce an increase in MAP
because increasing blood viscosity raises total peripheral resistance.
2. Click and drag on the slider to increase blood viscosity.
3. Answer the following questions:
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What happened to MAP?
Does this make sense to you?
Explain your observations and relate them to your hypothesis.
Mean arterial pressure will rise because an increase in blood viscosity will cause an increase in
total peripheral resistance.
4. Use the slider to decrease blood viscosity and observe what happens to MAP.
5. Answer the following questions:
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What happened to MAP?
Does this make sense to you?
Explain your observations and relate them to your hypothesis.
Conversely, a decrease in blood viscosity will produce a decrease in total peripheral resistance,
thus decreasing MAP.
Effect of Blood Vessel Radius on Mean Arterial Pressure
1. Formulate a hypothesis to predict the effect of an increase in blood vessel radius on MAP.
2. Formulate a separate hypothesis to predict the effect of a decrease in blood vessel radius on
MAP.
You should hypothesize that an increase in blood vessel radius will lower MAP by decreasing
total peripheral resistance. Conversely, a decrease in blood vessel radius will increase MAP (by
increasing total peripheral resistance).
3. Test each hypothesis by using the slider to change blood vessel radius and follow the effects
of these changes on MAP.
4. Answer the following questions:
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What happened to MAP after each change?
Do these effects make sense to you?
Explain your observations.
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Increasing blood vessel radius reduces total peripheral resistance; therefore, MAP decreases.
Conversely, decreasing vessel radius reduces total peripheral resistance and MAP.
5. In the cardiovascular disease called arteriosclerosis ("hardening of the arteries"), the
deposition of saturated fats and cholesterol along the inner lining of blood vessels reduces
vessel diameter.
6. Simulate this condition by decreasing the blood vessel radius.
7. Answer the following question:

What happens to MAP?
MAP increases because arteriosclerosis reduces blood vessel radius.
Effect of Heart Rate on Cardiac Output and Mean Arterial Pressure
1. Formulate a hypothesis to predict the effect of an increase in heart rate on cardiac output and
MAP.
2. Formulate a separate hypothesis to predict the effect of a decrease in heart rate on cardiac
output and MAP.
This assignment is designed to help you understand the factors that affect cardiac output. An
increase in heart rate will produce an increase in cardiac output and MAP. A decrease in heart
rate will decrease cardiac output and MAP.
3. Test each hypothesis by using the slider to change heart rate and follow the effects of these
changes on cardiac output and MAP.
4. Answer the following questions:
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What happened to cardiac output after each change?
What happened to MAP after each change?
Do these effects make sense to you?
Cardiac output and MAP will increase following an increase in heart rate. Cardiac output and
MAP will decrease following a decrease in heart rate. These effects are explained by the
following equation: CO = SV (stroke volume) x HR (heart rate). The increase in blood flow
produced by an increase in CO results in greater pressure on the walls of systematic arteries.
Effect of Stroke Volume on Cardiac Output and Mean Arterial Pressure
1. Increase stroke volume by increasing diastolic ventricular volume, and then observe what
happens to cardiac output and MAP.
2. Answer the following questions:
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Why did increasing diastolic ventricular volume produce an increase in stroke volume?
What happened to cardiac output and MAP when stroke volume was increased?
Diastolic ventricular volume is the amount of blood that fills each ventricle at the end of ventricular
diastole (relaxtion). Because this volume is increased, stroke volume (the amount of blood
pumped by each ventricle during ventricular systole) is increased. Increased stroke volume
produces an increase in CO.
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Based on what you know about stroke volume, what is another way that stroke volume
can be increased using CardioLab?
Stroke volume will increase by decreasing systolic ventricular volume--the amount of blood that
remains in each ventricle following ventricular systole.
3. Once you have answered this, use CardioLab to verify or refute your answer.
4. Be sure that you understand the basic relationships between MAP, resistance, and cardiac
output before continuing.
Exploration Experiment: Blood Pressure Homeostasis
Once you have a comfortable understanding of the relationships between MAP, cardiac output
(CO), and resistance, you can use CardioLab to perform experiments that will help you
understand the many mechanisms involved in blood pressure homeostasis.
1. Click the To Experiment button at the lower left corner of the screen to leave the Equation
view.
The Variables view that now appeas provides you with many options for designing an
experiment. A number of different conditions (variables) can be manipulated using this feature to
help you understand blood pressure homeostasis and the relationships of hemodynamics.
Notice that you can use sliders to manipulate heart rate, vessel radius, blood viscosity, systolic
ventricle volume, blood volume, and venous capacity-the amount of blood contained within
systemic veins. You can manipulate these variables to study the effects of each variable on
important measures of cardiovascular system physiology and to demonstrate how the human
body controls many different aspects of the cardiovascular system during homeostasis.
When you run an experiment in which you have changed any of these variables, the simulation
will ultimately return each variable to normal (default values), allowing you to examine how each
variable responds to the experimental manipulation that you created. For each experiment, you
are provided with output data using chart recordings for five important measures of
cardiovascular activity and hemodynamics. These include the following:
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Mean Arterial Pressure (mm Hg)
Heart Rate (beats/min)
Stroke Volume (ml)
Total Peripheral Resistance (dyne-s/cm5)
Blood Volume (L)
The time frame for each recording is in seconds. A numerical value for each parameter will also
appear in the far right column of these recordings. Note: The numerical values for each recording
can be saved in your lab notebook by clicking on the Export Text button at the lower left side of
the screen. A separate window will open. From this window, you can save this data.
2. Review the other functions of CardioLab by clicking on each tab at the top of the screen.
Activity 1: Normal Values of Cardiovascular Physiology
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You must understand what the normal values for each parameter are before you manipulate any
of these parameters.
1. In the Variables view, click on the Start button to begin the simulation.
2. When the normal values for mean arterial pressure, heart rate, stroke volume, total peripheral
resistance, and blood volume hit the 15-second mark, click on the Stop button.
3. Click on the Export Text button to record the values.
4. Copy and paste your data into Appendix__, CardioLab Report.
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Important: After you have recorded the value, do not close your lab notebook. To
continue with your experiment, minimize your notebook.
5. Carefully examine the normal values for mean arterial pressure, heart rate, stroke volume,
total peripheral resistance, and blood volume.
6. Look at both the patterns of each recording and the numerical values for each measure
(shown at the far right of each recording). Be sure that you are comfortable with the normal
values for each parameter before moving to the next exercise.
7. Click on the Start button to restart the normal values.
8. Click on the Nerve Impulses view to study electrical activity in a normal patient.
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Notice that several different tracings are shown.
Below is a description of the purpose of each recording.
o
Carotid Sinus: this recording is measuring electrical activity from a cluster of neurons
that are located in the wall of each internal carotid artery. These neurons are called
baroreceptors because they sense blood pressure in the carotid artery and send
electrical impulses to the medulla oblongata of the brain. Baroreceptors are very
important for the feedback mechanisms involved in blood pressure homeostasis.
Impulses from the baroreceptors are integrated in the medulla to control ANS
neurons, which in turn can increase or decrease heart rate or influence blood vessel
diameter according to blood pressure changes in the carotid artery.
o
Vagus: this recording is measuring electrical activity of the vagus nerves. The vagus
nerves are cranial nerves that transmit approximately 75% of parasympathetic
nervous system activity in the human body. Activity of the vagus nerves regulates
heart rate in addition to regulating the involuntary functions of many other body
organs. The vagus nerves innervate the SA and AV nodes of the heart. Electrical
impulses from these nerves inhibit activity of the SA and AV nodes to decrease heart
rate.
o
Sympathetic Cardiac: this recording is measuring electrical activity of the sympathetic
cardiac nerves. As their name indicates, these nerves are part of the sympathetic
division of the ANS. Sympathetic cardiac nerves innervate the SA and AV nodes.
Electrical impulses from these nerves increase activity of the SA and AV nodes to
increase heart rate.
o
Sympathetic Vasoconstrictor: this recording is measuring electrical activity of
sympathetic nervous system nerves that are innervating smooth muscle cells in the
walls of systemic arteries. Recall that few arteries are innervated by parasympathetic
neurons. Sympathetic innervation of the arterial wall is primarily responsible for
changes in the diameter of arteries. In general, stimulation of these nerves triggers
vasoconstriction of systemic arteries while a decrease in electrical activity in these
nerves triggers vasodilation of systemic arteries.
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9. Answer the following question in Appendix L: CardioLab Report:
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What are the normal values for each electrical activity?
10. Click on the Stop button to stop this simulation.
11. Click on the Reset All button to reset the simulation.
Activity 2: Effect of Heart Rate
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, consider the following points:

What effect will a change in heart rate have on each of the five other parameters
indicated in the Variables view?
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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.
o
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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?
Studying these changes will help you understand how the human body will compensate in an
attempt to maintain blood pressure homeostasis.
Set up an experiment to answer the questions above as follows:
1. Click on the Start button and allow normal recordings to continue for 5 seconds.
2. After 5 seconds, click and hold on the slider for heart rate and increase heart rate to the
maximum value for this slider.
3. Click on the box next to this slider to freeze heart rate at this value.
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Notice that you have increased heart rate.
4. Look at the slider bars for vessel radius, blood viscosity, systolic ventricle volume, blood
volume, and venous capacity.
5. Observe what is happening to each of these parameters.
6. Answer the following questions by completing the table in Appendix L: CardioLab Report:
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Which parameters changed and how did each parameter change? For example, what
happened to vessel radius? Did vessel radius increase or decrease? Why?
Did any parameter(s) remain unchanged? If so, which one(s)?
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.
An increase in heart rate will produce the following changes
in each of the five other parameters:
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Vessel Radius
Blood Viscosity
Systolic Ventricle
Volume
Blood Volume
Venous Capacity
7. Once you have answered these questions, stop the simulation and repeat this experiment.
This time, look at the tracings at the bottom of the screen and take note of any changes in
each output parameter.
8. Answer the following questions in Appendix L: CardioLab Report:
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Did mean arterial pressure return to normal? Why or why not?
What happened to stroke volume? Peripheral resistance? Blood volume? Explain your
answers.
9. Stop the simulation and repeat this experiment. This time, look at the Nerve Impulse tracings
and take note of any changes that you see.
10. Answer the following questions in Appendix L: CardioLab Report:
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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.
Activity 3: Effect of Blood Viscosity
As you learned in the first assignment, blood viscosity can decrease due to different anemias,
and increase due to polycythemia. In the self-check experiment, you looked at the effect of
changes in blood viscosity on MAP; however, you did not study how the cardiovascular system
will respond to viscosity changes in an effort to maintain blood pressure homeostasis.
1. Repeat the steps described in Activity 2 above; however, this time instead of changing heart
rate, increase blood viscosity.
2. Answer the following questions in Appendix L: CardioLab Report:
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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.
Did MAP return to normal? Why or why not? Explain your answers.
References
CardioLab assignments and answers were adapted with permission from Pearson Education, Inc.
Biology Labs On-Line is a collaboration between the California State University system and
Benjamin Cummings.
© 2002 California State University and Benjamin Cummings, an imprint of Pearson Education,
Inc. Development was partially supported by a grant from the U.S. National Science Foundation.
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