Assignments for non-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.