This is the second Investigation of the LabLearner CELL Examining Exercise.

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A. Begin this Investigation by reviewing the flow of blood through the heart, lungs, and body. Initiate a discussion by asking students the questions that follow.

1. Ask students: Why is it important for athletes to understand the cardiovascular and respiratory systems? Athletes know that in order to perform to their maximum ability they must provide their bodies with plenty of oxygen.  They realize that they must increase the ability of their cardiovascular and respiratory systems to provide the body’s muscles with an adequate supply of oxygen as they exercise.  The more oxygen the muscles receive, the better an athlete can perform.  Therefore, athletes must know what exercises to include in their overall program to increase the efficiency of their cardiovascular and respiratory systems.

2. Ask students: Why is it so important for the body to have a plentiful supply of oxygen? In order for any muscle or organ to function, it must have oxygen.  If the oxygen supply is not sufficient, the cells and organs in the body cannot perform.

3. Ask students: What would happen if one of the two systems could not function properly? If the respiratory system did not function properly, then a sufficient supply of oxygen could not enter the blood to keep the body’s cells and organs functioning.  If the cardiovascular system did not function properly, oxygenated blood could not reach the cells and organs.  This would deprive the cells and organs of the body of oxygen and they could not function properly.  If carbon dioxide is not released from the body, it would build up in the blood, which is toxic to the body.

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4. Briefly review the flow of blood with students:

a. The heart pumps the blood from the lower chamber on the left side of the heart.  The chamber is called the left ventricle.  From the left ventricle, blood is pumped into the aorta, the main artery that leaves the heart.  This blood is rich in oxygen.

b. The blood flows from the aorta through smaller arteries, which eventually lead to tiny capillaries.

c. The oxygen and nutrients in the blood move through the thin walls of the capillaries into the cells and organs of the body.

d. Carbon dioxide and waste products move from the cells and organs of the body through the capillary walls into the blood located in the capillaries.

e. The blood flows from the tiny capillaries into the larger veins.  This blood contains very little oxygen and a relatively large amount of carbon dioxide.

f. This oxygen poor blood flows from the veins into the right atrium of the heart.  The right atrium is the top chamber on the right side of the heart.

g. The blood moves from the right atrium through the tricuspid valve into the right ventricle, or lower right chamber.

h. From the right ventricle, blood flows through the right and left pulmonary arteries into the right and left lungs.

i. In the lungs, oxygen is transferred from the lungs into the blood and carbon dioxide from the blood into the lungs.  This transfer occurs at the level of the alveoli of the lungs and capillaries surrounding the alveoli.  The alveoli are tiny air sacs in the lungs.

j. The blood flows from the right and left lungs through the pulmonary veins to the left atrium of the heart.  

k. From the left atrium, blood flows through the mitral valve into the left ventricle, where the entire process begins again.

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B. Direct students to locate their Physical Fitness Log at the end of their Student Data Record. 

Ask students to organize into their exercise pairs.  These are the same pairs they had when performing their exercises in the Lab and PostLab of Investigation One.

1. Direct students to follow the same procedure to complete their exercises as in the Lab and PostLab of Investigation One.  Each student in the pair should perform the same exercise as he/she did in Investigation One.  This means that the two students will perform different exercises; one will perform the jump rope exercise and the other the left lifts.

2. Students should first take and record their resting heart rates in the appropriate column of their Physical Fitness Log before beginning their exercises.

3. Each student should perform their exercise; either the leg lifts for each leg for 45 seconds or the jump rope activity for two minutes.

4. After students have completed their exercises, they should immediately take and record their heart rates in their Physical Fitness Log.

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C. The experiments in Investigation Two will focus on changes in heart and respiratory rate. Before discussing the experiments with students, provide students with an opportunity to reflect on the concept of heart rate and to help them check their understanding of all the concept implies.

1. Ask students:  In your Physical Fitness Log you measured your heart rate while sitting, before beginning your exercises. The name given to this measurement is resting heart rate.  What do you think that means? Resting heart rate refers to the number of times the heart beats in a minute when the body is at rest.

2. Ask students:  Look at your resting heart rate for the first two entries in your Physical Fitness Log.  Was your resting heart rate today the same as your previous results? Student answers may vary, but most students should reply that their resting heart rate was very similar to their previous results.

3. Ask students:  Why do you think the resting heart rates were similar? Students should suggest that in all cases they were not performing exercises, but were sitting.  Therefore, the rates should be similar.

4. Ask students:  What if someone asked you what your resting heart rate was? Which number would you tell them? Student answers may vary.  This question is designed to illustrate that although the heart rates are similar, there are still differences and students may wonder how they would know which value they should choose.

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5. Tell students that one way they can answer the question would be to determine their average or mean resting heart rate.  The average or mean resting heart rate takes into account all of the resting heart rates over several days and generates one value.  It is a way of saying that on any day, my heart rate will be around this value.

6. In order for students to participate in this Investigation, they will need to understand the method for calculating an average or the mean value.

a. Explain that an average or mean represents the middle point of a set of numbers, or values, with the same function.  

For example: Harry buys an apple that costs 20 cents.  The next day, he buys and apple for 22 cents.

b. Ask students:  What is the average cost Harry paid for an apple?  Illustrate the calculation on the board (see slide).

Apples cost:  20 cents and 22 cents

Add together the values in the set, then divide by the number of values in the set 

Therefore:  20 cents + 22 cents = 42 cents ÷ 2 = 21 cents

21 cents is the average cost Harry paid for an apple.  It can also be referred to as the mean price Harry paid for an apple.

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7. Ask students:  What is your average or mean resting heart rate?

a. Tell students to record the three heart rates they recorded in the Physical Fitness Log before performing their chosen exercise in Problem 1a of their Student Data Record.

77 beats per minute

72 beats per minute

70 beats per minute

b. Instruct students to calculate their average resting heart rate by adding the three heart rates they recorded and then dividing the total by three.  A step-by-step process is provided in Problems 1b through 1c to aid students and is also illustrated below on this slide.

8. Explain to students that scientists have determined that the average resting heart rate for children under ten is 70 – 120 beats per minute and the average resting heart rate for children over 10 and adults is 60 – 100 beats per minute.

9. Ask students:  How do you think scientists determined the range for the average resting heart rate? Student answers will vary.  

The scientists performed calculations similar to the ones just done in the lab, but for many people of many different ages.  These scientists compiled the resting heart rates of many individuals of various ages.  Then they grouped those individuals by age and looked at the heart rates of the age groups included.  Because heart rates vary slightly, the scientists grouped the rates in a range into which most individuals’ heart rates fell.

10. Ask students:  How does your average resting heart rate compare to the range determined by scientists? Most students in sixth grade, or 12 years of age, would have a resting heart rate in the range of 80 to 90 beats per minute.  Therefore, students would have a resting heart rate that falls in the middle range for their age group (children ten and over).

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11. Ask students:  Based on today’s data, how would you calculate the mean resting heart rate for the class shown on this slide?

a. Ask students:  How could we organize a table for recording the data?  After working with students to determine the organization of the Table, draw it on the board.  As you discuss the organization of the Table, encourage students to refer to their Procedural Toolbox.  A sample table is provided below.  Extend your table to include a row for each student.

b. Tell students to record their resting heart rate for today in the table on the board.

c. Using the heart rates students obtained during today’s exercises, direct them to total the heart rates and record the answer in Problem 2a of their Student Data Record. Record the number on the board.

90 + 86 + 85 + 81 + 80 = 422

d. Instruct students to calculate the mean, or average, heart rate for the class.  Direct them to divide the total heart rate by the number of students (heart rates).   Students should record this in Problems 2b-2c in their Student Data Record.

422 ÷ 5 = 84.4

e. Ask students:  How does the mean resting heart rate for the class compare to the range? It is within what is considered the normal range for the average resting heart rate.

f. Ask students: What does this indicate? As a whole, the class represents children that are healthy.  

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D. Explain that in Investigation Two, in addition to investigating heart rate, students will investigate respiration and other benefits of exercise.  Review some of the terms in the Scientist’s Glossary.

1. Ask students:  What do you think the term respiratory rate means? Students should realize that this is a measurement due to the term “rate,” just as heart rate is a measurement.  Also, since respiratory is included in the term, the measurement must be of a component of the respiratory system, most likely the lungs.

2. Ask students to locate the term in their Scientist’s Glossary.  Ask them to compare their prediction to the actual definition for the term respiratory rate – the measure of how many times a breath is performed in one minute.

3. Ask students:  What would one breath include? One breath includes one inhalation followed by one exhalation.

Important Note: This slide provides an opportunity to review the spring scale model of the involvement of the diaphragm and lung volume developed in Investigation 1 Lab:

Inhalation involves contraction of the muscular diaphragm, which increases lung volume and sucks in fresh air.

Exhalation involves relaxation of the muscular diaphragm, which decreases lung volume and forces out CO₂-rich waste gas.

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4. Tell students they will perform an exercise that will help them practice calculating their respiratory rate.  Ask students to locate Problem 3 of their Student Data Record.

a. Instruct students to count how many times they breathe during a 30-second period.  Time the interval for students using a timer or clock with a second hand.

b. Direct students to multiply the number by two to obtain a rate of one minute and record that number in Problem 3a in their Student Data Record.

c. Next, request students hold their breath for a 30-second interval, and carefully observe how they feel at the end of this time period.  They should record their observations in Problem 3b.

d. Time another 30-second interval during which students again count how many times they breathe.  Record the respiratory rate in Problem 3c as a one-minute measurement.

5. Discuss this respiratory rate exercise.  The following questions can be used to help initiate the discussion.

a. Ask students: What happened when you held your breath? Student answers may vary. Students may have had some difficulty holding their breath for the 30-second interval.  They may also have felt their heart beating harder or felt slightly dizzy.  After breathing again, they may have had to breathe faster and deeper than usual.

b. Ask students: Did you observe a difference between the two respiratory rates you recorded? If so, how did they differ? Yes.  The respiratory rate after holding the breath was higher than the resting respiratory rate.

c. Ask students: Why do you think the difference occurred? Student answers will vary. The difference may have occurred because the body was deprived of a regular oxygen supply.  The more frequent and deeper breaths were a reaction designed to increase the oxygen flow into the blood.

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6. Discuss the terms cardiac output, cardiovascular endurance, cardiovascular fitness, respiratory fitness, and cardiovascular training with the class, indicating that students will understand some of these terms better after their lab experiments.

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E. Tell students they will explore the effects of exercise on the body as they continue with this Investigation.  As they conduct their experiments, they should think about the following questions:

What do Olympic athletes do to increase their cardiovascular and respiratory fitness?

Why is exercise important?  What are the benefits of exercise?

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