David L. Umbarger, Montezuma-Cortez High School, Cortez, CO BLOOD CIRCULATION LAB Appropriate for grades 9-12. OVERVIEW: This activity is designed to let students see blood moving in the fin of a fish. They then can observe how the hormone epinephrine (adrenaline) changes the flow of blood. PURPOSE: A goldfish is wrapped in water soaked absorbent cotton and placed in a large petri dish. A glass slide is placed under and another over the caudal fin to hold the fin in place and help restrict the fish from flipping the fin from position. When positioned under a light microscope, the circulation of blood can easily be observed, as well as the movement of blood from arterioles to capillaries and to veinuoles. When epinephrine (adrenaline) solution is added topically to the fin, the response of the vessels can be observed. OBJECTIVES: The student will be able to: 1. Compare and contrast the structure and function of arteriole, capillary, and veinuole. 2. Relate the circulatory vessels found in a fish to the found in humans. 3. Discuss how some hormones or drugs influence the distribution of blood. ACTIVITIES: 1. Give the following questions as a pre-lab activity: a. What direction would you expect blood to flow through the following structures in a fish fin: Arteriole? Veinuole? Capillary? b. What are the primary differences between the structures listed above? c. What effect would you expect epinephrine (adrenaline) to have on the circulation of blood in the fin of a fish? 2. Completely saturate enough absorbent cotton with aquarium water to completely surround a goldfish from the aquarium and wrap it in the cotton and place it in a petri dish. Place a glass slide under the caudal fin of the fish and then place another over the fin. Make sure there is enough aquarium water in the petri dish to keep the cotton very wet, yet not so much to cover the bottom slide under the fish fin. Position the fish fin on the microscope stage such that you can observe the fin, near its distal portion, through the microscope using the low power lens (you will probably need to lower the light by adjusting the diaphragm to a smaller setting. Familiarize yourself with the flow of blood to the fin by moving the petri dish around as you observe through the microscope (Remember, the microscope inverts images. Therefore, blood that appears to be flowing from the fin to the body is actually flowing from the body to the fin.) Locate an arteriole, veinuole, and capillary in the fish fin. After finding each structure, turn to the medium powered lens and observe. After each observation answer the questions relative to the three structures: a. What relative size is this structure? b. With what relative velocity does blood move in this structure? c. What direction does blood flow in this structure? (toward head or tail) d. Does blood move at a constant rate and in one direction or in both directions and at different rates? 3. How hormones effect circulation. Locate a position on the fish fin under the microscope where an arteriole and a capillary may both be observed at the same time (use low power). While one person observes the blood flow, an assistant should add two drops of epinephrine solution to the fish fin just cranial to where the fin is positioned under the microscope slide. The following questions should then be answered after returning your fish to a designated aquarium: a. What observed reaction did the epinephrine have in the rate of blood flow in the arteriole and capillary? b. Under what conditions would you expect a fish to naturally secrete epinephrine? c. After observing the effect epinephrine has on the circulation of blood in a fish fin (question a.), expand on your answer in question b. to include an evolutionary advantage the fish might obtain by secreting epinephrine when under those conditions. d. Based on your observations, under what conditions would you secrete epinephrine, what effect would you expect it to have, and what evolutionary advantages would you expect it to provide? RESOURCES/MATERIALS NEEDED: All described above. TYING IT ALL TOGETHER: When administering the epinephrine, the students will expect an increase in the fishes' blood flow based on their knowledge of adrenaline being a cardio-vascular stimulant. However, it restricts blood flow to the peripheral circulatory network. Their observations serve as a good test for their ability to separate what they bring in the lab as a preconceived expectation from the actual observed effect. You might follow this lab with a discussion of the need for a placebo or other controls when doing labs of this nature. Other drugs such as ethanol or nicotine may be used by some groups and the results compared on the board after the lab.
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