Am I Getting Anywhere? Physics of Blood Flow-Velocity. Student Data Page, Activity 3C

Transcription

1 Am I Getting Anywhere? Physics of Blood Flow-Velocity Student Data Page, Activity 3C Getting Started: 1. Go to the section of the model assigned to you to watch for leaks. 2. Turn on the pump. 3. Allow the pump to stay on for 1 minute. 4. You are ready to begin the lab if there are no leaks. I. Check out the model: Do you remember seeing or building a small volcano that erupts with a baking soda and vinegar mixture? Have you ever seen a model of the solar system? Models represent an object or working system. What are some other models you might remember? Why do you think people use models? This model is going to help us understand what happens in a very tiny artery that supplies the heart muscle with food and oxygen one of the coronary arteries. In particular, this model represents the descending coronary artery. The vessel splits into two smaller vessels at a point generally called a bifurcation. Models are not perfect so they are said to have limitations. As liquid is moving through the model, think about how this model compares to what you have learned about the structure and function of the human blood vessels and other parts of the cardiovascular system. 1. Compare the model to what you know about blood vessels in the cardiovascular system. Write down your group ideas. Draw a diagram to illustrate your observations. Responses and Drawings 2006 The University of Texas Health Science Center at San Antonio 13

2 The blood vessel model is going to help us see and learn basic ideas about what happens to the velocity of blood as it travels through healthy blood vessels and blood vessels with atherosclerosis. You will be using model red blood cells (RBCs) to help you observe the velocity of the blood. II. Blood Velocity in a Healthy Blood Vessel It s time to calculate and graph the velocity of blood in a model healthy blood vessel. Decide upon the group roles as described on the task cards. Be sure each person understands his or her job BEFORE beginning the lab. Read each step and check off as it is completed. 1. Stop your pump and allow the water to drain. Mark sections A, B, C on the blood vessel model as shown on Figure cm 20 cm 20 cm Section A Section B Section C Figure 1 Marking Sections 2. Assign the following jobs described below: Pump Engineer 1. Make sure all group members are ready and then turn the pump on 2. Turn the pump off after section C has been timed. 3. Monitor the model for leaks 4. Monitor all connections RBC Spotter 1. Drops the RBC model into the blood vessel model 2. Directs timers to start and stop the stopwatches 3. Retrieves RBC models Timer for Section A 1. Start and stop the stopwatches to time the velocity of the RBC through their section of the model 2. Clearly call out the results so the Recorder can record the data Timer for Section B 1. Start and stop the stopwatches to time the velocity of the RBC through their section of the model 2. Clearly call out the results so the Recorder can record the data Timer for Section C 2006 The University of Texas Health Science Center at San Antonio 14

3 1. Start and stop the stopwatches to time the velocity of the RBC through their section of the model 2. Clearly call out the results so the Recorder can record the data Recorder 1. Records all data for the lab 2. Ensures that all directions are being followed 3. Ensures that all members of the group copy the data tables The Pump Engineer will start the pump once everyone is ready. The RBC Spotter will locate the bag of red blood cells (RBCs) and drop one into the start of the blood vessel. Observe how the RBC moves through the blood vessel. What do you observe about the movement of the RBC? The RBC Spotter will now drop another RBC into the blood vessel and once the RBC travels to the start of Section A he/she will tell all three of the timers to start their stopwatches. The RBC Spotter will say A stop! when the RBC floats to the end of section A and Timer for Section A will stop his or her watch. The RBC Spotter will say B stop! when the RBC floats to the end of section b and Timer for Section B will stop his or her watch. The RBC Spotter will say C stop! when the RBC floats to the end of section C and Timer for Section C will stop his or her watch. 9. *This may take some practice so you may want to try a few practice runs. Recorder will record the data from Timers A, B, and C in the Time (seconds) column of Table 1 on this Student Data Page and will make sure everyone in the group copies it onto their own papers. 10. Repeat the experiment two more times. Pump Engineer will stop the pump when all three sets of data are collected. 11. Complete the rest of Table 1 by calculating Section Time (seconds) and the averages The University of Texas Health Science Center at San Antonio 15

4 Table 1 Healthy Blood Vessel Time (seconds) Section Time (seconds) Trial Time A Time B Time C Section A (Time A) Section B (Time B Time A) Section C (Time C Time B) # 1 # 2 # 3 Average of each Section III. Processing out: 1. How would you describe the velocity of the RBC in a healthy blood vessel? 2. If your group saw changes in the velocity, what do you think caused these changes? IV. Blood Velocity in a Diseased Blood Vessel A stenosis (stenoses, plural) is a blockage that occurs inside of a blood vessel. Researchers have found a pattern in the location of these stenoses. They are usually found a few millimeters before a bifurcation. The stenosis usually begins to form here because of the physics of blood flow (hemodynamics). In the model you will be adding a stenosis in section B to see what effect this would have on the velocity of the blood flow The University of Texas Health Science Center at San Antonio 16

5 Make a hypothesis about what might happen to blood flow if you add a stenosis in the blood vessel. Read each step and check off as it is completed. 1. Find the bag labeled stenosis. Place the stenosis inside of section B as shown in Figure 1 Placing the Stenosis. Stenosis 20 cm 20 cm 20 cm Section A Section B Section C Figure 1 Placing the Stenosis Keep the same job assignments as before. The Pump Engineer will start the pump once everyone is ready. Follow steps 3-8 from Section II: Blood Velocity In A Healthy Blood Vessel Record your data from Timers A, B, and C in Table 2 on your Student Data Pages. Repeat the activity two more times. Stop the pump when you have collected 3 sets of data. As you did with Table 1, complete the rest of Table 2 in these Student Data Pages The University of Texas Health Science Center at San Antonio 17

6 V. Processing Out: 1. Was your hypothesis correct? Why or why not? 2. How would you describe the velocity in the diseased blood vessel (with stenosis) compared to the velocity in the healthy blood vessel? 3. Why do you think the velocity was different between the healthy and diseased vessels? 4. Did acceleration occur in the blood vessel? Explain The University of Texas Health Science Center at San Antonio 18