Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Cardiac contractility modulation wikipedia , lookup
Rheumatic fever wikipedia , lookup
Coronary artery disease wikipedia , lookup
Heart failure wikipedia , lookup
Antihypertensive drug wikipedia , lookup
Electrocardiography wikipedia , lookup
Myocardial infarction wikipedia , lookup
Quantium Medical Cardiac Output wikipedia , lookup
Heart arrhythmia wikipedia , lookup
Dextro-Transposition of the great arteries wikipedia , lookup
22 ss i RY 0- m inu te s e ACTIVITY OVERVIEW LA O 1–2 o5 on 40 -t s The Heart—A Muscle BO RA T SUMMARY Students evaluate the strength of the heart muscle by attempting to pump water at the same rate as their resting pulse (in beats per minute). They then compare the volume of water they pumped to the volume of blood the heart pumped in the same amount of time. KEY CONCEPTS AND PROCESS SKILLS 1. Graphing data can reveal patterns that are not apparent from data tables. 2. Creating models is one way to understand and communicate scientific information. 3. Systems in the human body help regulate the internal environment. For example, the heart rate changes to keep blood oxygen levels in the range required to survive. 4. Human body systems are composed of organs. The structure of an organ is adapted to perform specific functions within one or more systems. 5. Blood is pumped around the human body by the heart. The heart acts as a pump that works continuously without rest. 6. Valves control the direction of flow and allow liquid to move under pressure in both a pressure bulb and the human heart. 7. The heart pumps a large volume of blood with each beat. KEY VOCABULARY function range model structure muscle volume Teacher’s Guide B-135 Activity 22 • The Heart—A Muscle MATERIALS AND ADVANCE PREPARATION For the class * sponges * mops For each group of four students * 1 pressure bulb 2 45-cm (18-inch) lengths of clear plastic tubing 2 plastic bins (or buckets) 1 1-liter bottle or other measuring container, graduated into 100-mL divisions supply of water 1 meter stick (optional) * access to a wall clock or watch with a second hand * paper towels *Not supplied in kit If you do not have 1-liter flasks for measuring volume, ask students to bring in clean, empty 1-liter soft drink bottles. Use a permanent pen and a graduated cylinder to calibrate the volume in 100-mL divisions. If meter sticks are unavailable, use a measuring tape to mark heights in 1-inch increments on a wall so students can easily measure their height in feet and inches. To prevent potential spills, fill one plastic bin 3⁄4 full of water for each group of four students in advance. Also have sponges, mops, and paper towels available to clean up any spills. Alternatively, you could conduct this activity outdoors. TEACHING SUMMARY Getting Started 1. Discuss the heart as a muscle. Doing the Activity 2. Students record their resting pulse and then pump water. Follow-Up 3. B-136 Science and Life Issues The class compares the heart with other muscles of the body. The Heart—A Muscle • Activity 22 INTEGRATIONS Mathematics Reinforce graphing skills by having students create a bar graph of class data (of resting pulse, volume of water pumped, or volume of blood pumped by the heart). Discuss the range of student data. BACKGROUND INFORMATION Cardiac Output While the size of a person’s body significantly affects pulse rate, people of the same size can have a range of resting pulse values. People with a low pulse rate for their size generally pump a larger volume of blood per pump (known as stroke volume). Athletes tend to have low resting heart rates and high stroke volumes. The efficiency of the heart (as exhibited by a lower resting heart rate) is affected by a number of factors, such as overall physical condition, stress, metabolism, and use of medications. Cardiac output is the volume of blood the heart pumps out in a minute (stroke volume x pulse rate). The heart of an average adult at rest pumps approximately the entire volume of blood around the body once a minute. When exercising, an increase in the stroke volume and an increase in pulse rate work together to increase the cardiac output, up to five times the output at rest. Students can estimate their own cardiac outputs based on their heights (as presented in Figure 1 on page B-62 in the Student Book). (In fact, cardiac output is more closely related to body mass. However, height is easier to measure in the classroom and is not as sensitive a subject as body mass.) Cardiac output is an important indicator of heart health. It can be reduced if the heart valves are damaged and/or the arteries are narrowed because of heart disease. Reduced cardiac output will tend to increase the heart rate, and a faster pulse increases the workload on the heart. Reduced cardiac output will also reduce the amount of blood getting to the tissues, which causes fatigue, especially during exertion. The heart starts beating about 7 months before birth and keeps beating until death. This works out to be around 3 billion beats in an average life span. A baby has a pulse of about 130 beats per minute. By adulthood, most people have a resting pulse of about 70. The heart’s failure to keep beating is the leading cause of death in most developed countries. Teacher’s Guide B-137 The Heart—A Muscle • Activity 22 TEACHING SUGGESTIONS n GETTING STARTED 1. Discuss the heart as a muscle. Have students feel the muscles in their upper arms. n 2. DOING THE ACTIVIT Y Students record their resting pulse and then pump water. Ask, How is your heart muscle similar to and differ- In the first part of the activity, students measure ent from muscles in your arms? Responses may their resting pulse in beats per minute, as was done include that the heart muscle is not attached to in Activity 19, “Heart-ily Fit.” If necessary, review bones and that it works all the time. Students may how to measure resting pulse. wonder how the heart expands again after the muscle has contracted. It is partly due to the elastic recoil of the heart muscle; like the pressure bulb, the heart returns to its resting shape. Very fit people and young people tend to have more elastic hearts than others. Inform students that, when completing Step 4 of the Procedure, they should use one hand only and pump the bulb the same number of times as their resting heart rate in one minute. Many students will be able to pump at about the same rate as their heart (as measured by their resting pulse). If they are not able to Tell students that in this activity they will evaluate pump the bulb that number of times in a minute, how hard the heart muscle works, as well as the they should stop at the end of one minute and record amount of blood it is able to pump each minute. the number of times they were able to pump the bulb. Review the Challenge (“How can you measure how hard your heart muscle works?”) with the class. Point out that they will measure volume, which can be defined as the amount of space something occupies. This activity provides an excellent opportunity to assess students on either element (“Task Management” or “Group Participation”) of the GROUP GI INTERACTION (GI) variable. If you plan to use Remind students that as soon as they finish pumping the water each person should measure the volume of water pumped as well as record how his or her hand feels. This is especially important because all the water should be returned to the original container before the next student begins pumping. Have students work in groups of four to complete the Procedure. this assessment with your students, inform After they have completed the Procedure, make sure them in advance and be sure you have enough time they know, or can measure, their height. Students to evaluate every group. need this information to answer Analysis Question 2. (They may be surprised to find they are an inch taller than the last time they measured!) A few students may need help comparing their data to the chart. Teacher’s Guide B-139 Activity 22 • The Heart—A Muscle n 3. FOLLOW–UP SUGGESTED ANSWERS TO ANALYSIS QUESTIONS The class compares the heart with other muscles of the body. 1. Compare the pressure pump model to what Ask, Your heart is a muscle. Do you think it is stronger you know about your heart. In what ways or weaker than the muscles in your hand? The heart do you think the pressure bulb is a good model for is a very strong muscle that must work continuous- your heart? What were the weaknesses of the pres- ly. You may wish to point out that the heart is an sure bulb as a model for the heart? involuntary muscle and is controlled by the nervous system. Its ability to work continuously The pressure bulb modeled the pumping func- requires an uninterrupted blood supply, which is tion of the heart. It also has valves that force provided by the coronary arteries that are visible on water to go in one direction, just like in the the outside of the heart. heart. The pressure bulb is slightly smaller than a real heart and may not accurately approxi- After students have completed Analysis Question 1, mate the pressure that the heart exerts. you may want them to compare the range of resting pulses. Ask, How many of you were able to pump the 2. Use Figure 1, on the following page, to find same volume of blood as your heart does? Emphasize out how much blood your heart pumps per minute the idea that the heart pumps the same blood based on your height. through the body again and again. In an adult, the total volume of blood in the body is 5–6 L. If appro- a. Record the volume of blood (in liters) pumped by your heart each minute. priate, have students create a bar graph of class data (as described in the Integrations section). Responses are likely to range from 3–5 liters. Ask, You were able to rest the muscles of your hand at b. Compare the amount of blood your heart pumps the end of one minute. When do you think your heart each minute to the amount of water you were muscle rests? Although many students may answer able to pump: Was it more? Was it less? By how “never,” the heart does rest between beats. This is much? one reason why stimulating one’s heart through Students are likely to have pumped 1.5–3 liters. smoking, drugs, or high stress levels can be detri- If students report pumping more than 3 liters, mental. An extremely well-conditioned athlete, ask if they pumped with only one hand and such as a marathon runner who has a resting pulse whether they made a real effort to pump ap- of 30–40 beats per minute, has a heart that is not proximately the same number of times as their only pumping with great efficiency but one that is heart beats in a minute. Generally, students also getting more resting time. report that their heart pumps a greater volume of blood per minute than the volume of water they pumped with their hand. Some will find that their heart pumps two or more times as much volume as they pumped per minute. B-140 Science and Life Issues The Heart—A Muscle • Activity 22 4. Figure 1: Heart Output Why do you think that exercising regularly decreases your heart rate? Height (feet and inches) Volume of Blood (liters per minutes) Height (feet and inches) Volume of Blood (liters per minutes) 4'0'' 3.00 5'1'' 4.38 ing exercise. Ask them to consider how a faster 4'1'' 3.13 5'2'' 4.50 heart rate will affect the volume of blood being 4'2'' 3.25 5'3'' 4.63 4'3'' 3.38 5'4'' 4.75 pulses than the general public. However, their 4'4'' 3.50 5'5'' 4.88 hearts pump the same volume of blood as the 4'5'' 3.63 5'6'' 4.95 4'6'' 3.70 5'7'' 5.00 heart have more tensile strength, are more elas- 4'7'' 3.75 5'8'' 5.13 tic, can expand more, and can pump more 4'8'' 3.88 5'9'' 5.25 4'9'' 4.00 5'10'' 5.38 4'10'' 4.13 5'11” 5.45 4'11'' 4.20 6'0” 5.50 5'0'' 4.25 Just like other muscles, the heart muscle is strengthened by regular exercise. Have students think about what happens to the heart rate dur- pumped and how hard the heart is working. Well-conditioned athletes have lower resting average person. Each stroke of an athlete’s heart pumps more blood because the walls of the forcefully. This ability is lost very quickly, however, when training ceases. 3. Describe how hard your heart works by using quantitative and qualitative data from the activity. Hint: Be sure to look at your notes from this activity. The heart is a muscle that works hard. It beats about 60–80 times a minute and pumps between 3–6 liters of blood a minute. Using their hands to pump, most students will be able to approximate their resting pulse, but are likely to have pumped about half of the amount of fluid their heart pumps. Most students are also likely to report that their hand was very tired. This comparison can give them a feeling for how hard their heart muscle works. Teacher’s Guide B-141