Assignments for Majors

For your ease in completing each assignment, the background text relevant to the experiment that you will perform is in black text, instructions for each assignment are indicated by plain text, and questions or activities that you will be asked to answer are indicated by bold text.

The following assignment is designed to help you become familiar with the operation of CardioLab.

Assignment 1:
Getting to Know CardioLab: Factors That Affect Cardiac Output and Mean Arterial Pressure:

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.

1. Effect of Blood Viscosity on Mean Arterial Blood Pressure
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.

Develop a hypothesis to predict the effect of an increase in blood viscosity on blood pressure, then test your hypothesis as follows.

Click and drag on the slider to increase blood viscosity.

What happened to MAP? Does this make sense to you? Explain your observations and relate them to your hypothesis.

Use the slider to decrease blood viscosity and observe what happens to MAP.

What happened to MAP? Does this make sense to you? Explain your observations and relate them to your hypothesis.

2. Effect of Blood Vessel Radius on Mean Arterial Pressure
Formulate a hypothesis to predict the effect of an increase in blood vessel radius on MAP. Formulate a separate hypothesis to predict the effect of a decrease in blood vessel radius on MAP.

Test each hypothesis by using the slider to change blood vessel radius and follow the effects of these changes on MAP.

What happened to MAP after each change? Do these effects make sense to you? Explain your observations.

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.

Simulate this condition and explain what happens to MAP.

3. Effect of Heart Rate on Cardiac Output and Mean Arterial Pressure
Formulate a hypothesis to predict the effect of an increase in heart rate on cardiac output and MAP. Formulate a separate hypothesis to predict the effect of a decrease in heart rate on cardiac output and MAP.

Test each hypothesis by using the slider to change heart rate and follow the effects of these changes on cardiac output and MAP.

What happened to cardiac output after each change? What happened to MAP after each change? Do these effects make sense to you? Explain your observations.

4. Effect of Stroke Volume on Cardiac Output and Mean Arterial Pressure
Increase stroke volume by increasing diastolic ventricular volume, then observe what happens to cardiac output and MAP.

Explain why increasing diastolic ventricular volume produced an increase in stroke volume. What happened to cardiac output and MAP when stroke volume was increased?

Based on what you know about stroke volume, what is another way that stroke volume can be increased using CardioLab?

Once you have answered this, use CardioLab to verify or refute your answer.

Are you comfortable with the basic relationships between MAP and resistance? Be sure that you understand the relationships between MAP, resistance, and cardiac output before continuing with these assignments.

Assignment 2:
Getting to Know CardioLab: 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.

Click the To Experiment button at the lower left corner of the screen to leave the Equation view.

The Variables view that will now appear 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:

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 or printed 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 print your data using the print feature on your browser or you can save this data to a disk or to your hard drive.

Look at the other functions of CardioLab by clicking on each tab at the top of the screen.

In some experiments, you will use the Interventions feature to apply certain experimental conditions that affect the cardiovascular system. The Cases feature will be used to examine three different cardiovascular disorders, while the Nerve Impulses feature will be used to view electrical activity to and from the heart.

In this exercise you will examine the normal values for each output measure.

1. Normal Values of Cardiovascular Physiology
You must understand what the normal values for each parameter are before you manipulate any of these parameters.

In the Variables view, click on the Start button to begin the simulation. Carefully examine the normal values for mean arterial pressure, heart rate, stroke volume, total peripheral resistance, and blood volume. 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.

Click on the Nerve Impulses view to study electrical activity in a normal patient.

Notice that several different tracings are shown. Below is a description of the purpose of each recording.

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.

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.

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.

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.

Take note of the normal values for each electrical activity. In other experiments you will study how these electrical activities change in response to different conditions.

Click on the Stop button to stop this simulation, then click on the Reset All button to reset the simulation.

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 questions:

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?

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 these questions as follows:

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. Take note of the following:

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?

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.

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.

Did mean arterial pressure return to normal? Why or why not? What happened to stroke volume? Peripheral resistance? Blood volume? Explain your answers.

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.

Repeat the experiment described above, but this time decrease heart rate and answer the same questions presented for the increase-in-heart-rate experiment.

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 first assignment, 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.

Repeat the steps described in exercise 2 above; 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.

Did MAP return to normal? Why or why not? Explain your answers.

Repeat this process to study a decrease in blood viscosity.

Assignment 3:
Blood Loss Compensation

The Interventions feature of CardioLab is designed to test how well you understand the principles of hemodynamics by providing you with the opportunity to design simulations of patients with various changes in hemodynamics and then to intervene in an attempt to return heart rate and blood pressure to normal. One condition that you can simulate is hemorrhage-the loss of blood. A classic, immediate symptom of hemorrhage is a decrease in mean arterial blood pressure due to a decrease in blood volume. Hemorrhage can lead to inadequate circulation of blood, a general condition known as shock. There are several different forms of shock and conditions that can lead to shock; however, one common form of shock due to the loss of blood is called hypovolemic shock.

The cardiovascular system can respond to hemorrhage quickly by activating short-term compensatory mechanisms designed to maintain blood pressure homeostasis and avoid shock. Depending on the extent of blood loss, other long-term compensatory responses involving the kidneys and bone marrow can be stimulated. The following exercises are designed to help you study the effects of blood loss on the cardiovascular system.

1. Small Hemorrhage
How can we help a patient overcome problems due to hemorrhaging? In addition to the obvious and immediate treatment--stopping the blood loss--consider other treatments for a patient who is hemorrhaging.

Imagine that you are a nurse or a physician caring for a woman who has just delivered a child. Childbirth proceeded without complications and this woman is showing no outward signs of hemorrhaging. She is now sleeping comfortably. Although there are no outward signs of hemorrhaging, she is experiencing a small amount of (internal) bleeding from her uterus. Simulate this condition as follows:

Click on the Interventions tab at the top of the screen. Notice that Small Hemorrhage appears in the popup menu as the default condition. Click Start to begin the simulation, allow this to proceed normally for several seconds, and then click on the Apply Intervention button to induce a small amount of bleeding.

Carefully look for changes in each recording. Which parameters changed? Which remain unchanged? Explain these results. Does blood pressure return to normal in this patient due to homeostasis? If so, explain which parameters changed to allow her blood pressure to return to normal.

Repeat this experiment if necessary to observe all changes.

2. Large Hemorrhage
While homeostasis can often compensate for small losses in blood volume, large losses of blood (for example, a 20% loss of blood volume) typically require medical interventions to return blood pressure to normal. This exercise is designed to help you understand the effects of a large loss of blood.

A man is walking across the street in a busy city at rush hour and is accidentally struck by a delivery truck. Fortunately, a school crossing guard has noticed the accident and immediately calls for an ambulance. Upon arrival at the accident scene, the emergency medical personnel notice that this individual has been bleeding excessively from a wound to his leg. Simulate this condition as follows:

Click on the Start button to begin the simulation. In the Interventions view, click on the popup menu and select Large Hemorrhage, then click on the Apply Intervention button.

Notice the immediate decrease in blood volume. Note any other changes in cardiovascular parameters. How is this patient's cardiovascular system responding in an effort to achieve blood pressure homeostasis? What is happening to heart rate? Does this make sense? Why or why not? What is happening to stroke volume? What is happening to total peripheral resistance? Explain each observation.

Do these responses return blood pressure to normal?

If not, you will need to intervene as follows. Assume that you have taken appropriate measures to stop the hemorrhaging. Help this patient by increasing his blood volume through a blood transfusion. To do this, click on the Variables tab. Click on the slider for blood volume and gradually increase blood volume while monitoring blood pressure and heart rate. Give this patient more blood until you have given him enough to return his blood pressure and heart rate to normal. Hold blood volume steady until blood pressure and heart rate have stabilized.

What happened to other parameters of the cardiovascular system as you gave him more blood? Explain these changes.

You may need to repeat this experiment again to observe all changes as they occur. Hopefully, congratulations are in order for your role in helping this patient survive and recover from his wounds! If you were unable to maintain blood pressure in this patient, repeat the experiment.

Assignment 4:
Effects of Blood Volume Changes

In addition to hemorrhage, many other conditions can lead to changes in blood volume. These can include diet, hormonal imbalances, kidney disorders, and lung disorders among other conditions. These assignments are designed to help you understand the effects of increases and decreases in blood volume.

1. Increase in Blood Volume
Imagine that you are a nurse in a hospital caring for a man with a kidney infection and kidney stones. Because of these problems, this patient is not producing sufficient amounts of urine. He is receiving nutrients and antibiotics administered through an intravenous (IV) line. You just changed his IV bag to a new bag containing 1 liter (L) of solution, but you inadvertently adjusted this IV bag so that fluid is entering the patient too rapidly.

What may happen to this patient if the entire bag is administered? How will this increase in body fluid affect important cardiovascular parameters? Consider these questions before you begin the simulation.

Simulate this situation by clicking on the Start button to monitor cardiovascular parameters in a normal human. Allow this to proceed for a few seconds. In the Interventions view, select IV Infusion from the popup menu, then click on the Apply Intervention button twice in rapid succession to simulate the IV infusion of a large volume of fluid.

What happens to each of the following parameters: MAP, heart rate, stroke volume, total peripheral resistance, and blood volume? Does each response make sense to you? Explain each effect.

2. Decrease in Blood Volume (No Hemorrhage)
You are well aware that exercising on a hot day can lead to excess loss of fluids via sweat. Of course, one danger of excess fluid loss is dehydration. However, you may not realize that dehydration is not just the loss of sweat. Virtually all body fluids, both intracellular fluids and extracellular fluids such as plasma, cerebrospinal fluid, interstitial fluid, and synovial fluid, are shared and mixed in a dynamic fashion designed to maintain the total body water content of approximately 40 L in humans. Because of these fluid dynamics, a decrease in fluid from one compartment, such as the loss of fluid from sweat glands, produces a decrease in most of the other fluid compartments. Hence, excess sweating decreases blood plasma volume. This assignment is designed to study the effects of dehydration on the cardiovascular system.

Formulate a working hypothesis to predict the effects of a decrease in blood volume on MAP.

Simulate this situation by clicking on the Start button to monitor cardiovascular parameters in a normal human. Allow this to proceed for a few seconds, then in the Interventions view, select Dehydration from the popup menu and click on the Apply Intervention button.

What happens to each of the following parameters: MAP, heart rate, stroke volume, total peripheral resistance, and blood volume? Does each response make sense to you? Explain each effect. Relate these observations to your hypothesis.

Assignment 5:
Exercise and the Cardiovascular System

Exercise-induced effects on the cardiovascular system are largely due to changes in electrical impulses coming from neurons of the autonomic nervous system (ANS). These changes are designed to ensure adequate delivery of blood to exercising muscles. The following exercise will help you learn about the effects of exercise on the cardiovascular system.

Based on what you already know about the cardiovascular system and based on what happens to your heart rate when you exercise, think about how the ANS is responsible for exercise-induced changes. What role does the sympathetic division of the ANS play in the cardiovascular response to exercise? How does this occur? Ask yourself the same questions about the parasympathetic division of the ANS, and the role of baroreceptors. Also consider how each neural component changes when you begin to relax following exercise.

Click on the Start button to monitor cardiovascular parameters in a normal human. Allow this to proceed for a few seconds, then in the Interventions view, select Treadmill from the popup menu and click on the Apply Intervention button four or five times in rapid succession to simulate strenuous exercise.

Notice what happens to each cardiovascular parameter. Record any changes that occur and explain these results.

To observe what is happening to nerve activity, stop this experiment by clicking the Stop button. Click the Reset All button. Repeat the experiment as before; however, before you apply the treadmill intervention, be sure to switch to the Nerve Impulses view to examine normal impulse activity. Once you have done this, apply the treadmill intervention as before, then return to the Nerve Impulses view to look at exercise-induced changes in nerve impulse activity.

What happened to impulse activity from each set of neurons? Describe your results.

Follow the activity of these neurons for several minutes until homeostasis of blood pressure and heart rate is achieved, then answer the following questions:

Describe the role of each set of neurons in blood pressure homeostasis. Which components of the cardiovascular system were affected by each group of neurons?

Assignment 6:
Neural Control of the Cardiovascular System

As described in the background text for this laboratory, homeostasis of blood pressure is achieved through ANS control via two mechanisms-regulating heart rate and controlling blood vessel diameter. Neurons from both the sympathetic division and the parasympathetic division of the ANS utilize neurotransmitters to mediate these changes. Recall that neurons of the sympathetic division release epinephrine onto heart cells and smooth muscle cells in the walls of blood vessels, while neurons of the parasympathetic division rely on the neurotransmitter acetylcholine. This assignment is designed to examine the effects of both neurotransmitters on heart rate, blood vessel diameter, and resulting changes in cardiovascular parameters.

1. Fight-or-Flight Response of the Sympathetic Nervous System
On the way home from meeting a friend for dinner, your car breaks down in a dark alley in an unfamiliar town at 1:30 a.m. The battery on your cell phone is dead, so you need to walk to the closest pay phone to call for help. As you walk down the alley you can feel the fight-or-flight response of your ANS starting to take effect as your heart rate increases, your temples throb, your pupils dilate, and you start to sweat. Simulate this situation as follows:

Click on the Start button to monitor cardiovascular parameters in a normal human. Allow this to proceed for a few seconds. In the Interventions view, select Epinephrine from the popup menu, then click on the Apply Intervention button once. Go to the Nerve Impulses view and observe what is happening to the activity of each group of neurons. Explain your results. You may need to switch back and forth between the Nerve Impulses view and the Interventions view to explain how changes in nerve impulse activity may relate to changes in cardiovascular parameters such as heart rate and total peripheral resistance.

2. Medical Uses of Epinephrine
Injections of epinephrine are used to treat certain patients with heart problems.

Can you think of a condition or multiple condition(s) when it might be helpful to treat someone with epinephrine?

Design an experiment to mimic this condition, then carry out this experiment using CardioLab.

Assignment 7:
Chemical Effects on the Cardiovascular System

In addition to the neurotransmitters that regulate the cardiovascular system, a variety of other commonly used chemicals--such as nicotine and caffeine, medicinal drugs, and illicit drugs--strongly influence heart rate. One example of an illicit drug with such effects on the cardiovascular system is cocaine. You may be aware of cocaine-induced heart attacks from several widely publicized cases involving athletes and professional actors. Cocaine produces an increase in heart rate and is also a potent stimulator of vasoconstriction.

Another chemical that strongly influences heart rate is foxglove, also known as digitalis. Foxglove is derived from flowering plants in the genus Digitalis. Dried leaves from Digitalis purpurea can be prepared in powdered form as a potent source of foxglove. Foxglove is a compound that functions as a vasodilator and also as a cardiotonic drug--a drug that increases contraction strength of the heart. Foxglove is often used for the treatment of patients with a cardiovascular disorder known as congestive heart failure. You will simulate the use of foxglove on patients with congestive heart failure in the next assignment. The following assignment is designed to help you examine the effects of foxglove.

Click on the Start button to monitor cardiovascular parameters in a normal human. Allow this to proceed for a few seconds, then in the Interventions view, select Foxglove from the popup menu and click on the Apply Intervention button once.

What happens to heart rate and blood pressure after you give foxglove? What happens to total peripheral resistance? Explain your results.

Assignment 8:
Cardiovascular Disorders

Unfortunately, cardiovascular disorders are fairly common in the United States. These assignments are designed to help you understand how three relatively common disorders influence the physiology of cardiovascular organs.

1. Congestive Heart Failure (CHF)
It has been estimated that over 8 million people in the United States and Europe suffer from congestive heart failure. This condition is a progressive disorder characterized by a decrease in cardiac output, and consequently blood flow, due to a number of different problems. In many patients with CHF, the problem is due to an enlarged left ventricle that is weak and ineffective at adequately pumping blood into the cardiovascular system. In other patients, damage to muscle cells in the walls of the left ventricle prevent the ventricle from maintaining normal cardiac output. In either case, because the left ventricle is unable to pump with the same effectiveness as the right ventricle, blood backs up into the pulmonary circuit, creating "congestion."

In the Cases view, start an experiment to follow normal heart rates. After a few seconds, stop the normal run by clicking the Stop button. Simulate CHF by selecting Congestive Heart Failure from the popup menu and then clicking on the Apply Case button. To begin the simulation, click the Start button. Observe what happens to each of the cardiovascular parameters in a CHF patient. Follow this patient for several seconds until you have a clear picture of which cardiovascular parameters may be changing. Note: In the Cases view, if you are already running an experiment you cannot just "give" a patient a disorder. You have to stop the simulation. Apply the case and then click Start to run the chosen case.

Describe the symptoms that this patient is experiencing. Do they make sense to you based on what you know about CHF? Why or why not?

In the previous exercise you studied the effects of foxglove (digitalis) and learned that it is often used to treat CHF.

Simulate this treatment by returning to the Interventions view. Select Foxglove from the popup menu, then click on the Apply Intervention button.

What effect does foxglove have on cardiovascular parameters in the CHF patient? Carefully study any changes in cardiovascular parameters and describe what these changes are.

2. Hypertension
Elevated blood pressure is called hypertension. Hypertension is a complex cardiovascular disorder with a number of different causes resulting from known risk factors such as stress, gender, obesity, and elevated levels of plasma cholesterol and saturated fats. Other cases of hypertension can be attributed to hormonal imbalances, kidney problems, and associated disorders in fluid balance in the body. In addition, there are a number of cases of hypertension for which the causes remain unclear. Because the development of hypertension is often multifactorial in nature, it can sometimes be very complicated to treat. Typically, hypertension is treated by trying to minimize risk factors that can be controlled in combination with the use of different drugs that affect heart rate and blood vessel diameter.

Simulate hypertension by selecting Hypertension from the popup menu and then clicking on the Apply Case button. Observe what happens to each of the cardiovascular parameters in a hypertensive patient. Follow this patient for several seconds until you have a clear picture of which cardiovascular parameters may be changing.

Think about which parameters you might want to manipulate to help this patient. Because many of the drugs that are used to treat hypertension affect heart rate and blood vessel diameter, see if you can use the Variables feature to lower blood pressure in this patient.

Discuss desirable effects that will lower blood pressure in hypertensive patients.

3. Mitral Valve Stenosis
The term stenosis refers to a "narrowing." In the disease called mitral valve stenosis there is a narrowing of the opening from the left atrium into the left ventricle, usually due to a thickening of tissue in the mitral (bicuspid) valve itself. Mitral valve stenosis is one of the most common types of heart valve disorders, particularly in women. Because of the stenosis, the flow of blood into the left ventricle is inhibited; therefore, blood will often backflow into the left atrium thus reducing flow into the aorta.

Simulate stenosis by selecting Mitral Valve Stenosis from the popup menu and then clicking on the Apply Case button. Observe what happens to each of the cardiovascular parameters in this patient. Follow this patient for several seconds until you have a clear picture of which cardiovascular parameters may be changing.

What happens to blood pressure in this patient? Based on what you know about the neural control of heart rate, discuss what is happening to heart rate and explain why this is occurring.

Assignment 9:
Group Assignment

In the previous assignments, you examined many different aspects of the cardiovascular system to learn about the homeostasis of blood pressure. Work together in a group of four students to complete these exercises.

Divide your group into pairs. Have each pair create a cardiovascular condition where one parameter has been changed to create an abnormal situation. Run the experiment and show it to the other pair in your group. Ask this pair to identify the problem and suggest possible interventions, then have them test their possible interventions to see if they can bring about the desired effect. Discuss the following questions.

Was the group successful in diagnosing the problem? Why or why not? Which interventions were suggested? Did the interventions work? Why or why not? Are the interventions that were suggested realistic manipulations that might be used in a clinical setting? Discuss your experiments and results with your instructor to help you answer this question.