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

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A. Begin this Investigation by directing students to locate their Physical Fitness Log from the end of their Student Data Record.  Ask students to organize into their exercise pairs.

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

2. Each student should perform their exercise, either the leg lift for 1.5 minutes for each leg, or jumping rope for four minutes.

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

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4. Explain that students will use their ongoing fitness experiment to review what they learned in Investigations One through Three.  Ask the students the following questions:

a. Ask students: What did you observe about your body during your exercises?  List students’ answers on the board. Student answers will vary, but should include references to increased heart rate, increased breathing rate, being winded, arms and legs being tired, etc.

b. Ask students: Which body systems are related to these effects?

c. What does this table tell you about how these systems work together?  When we exercise, we exercise all three systems.  It also tells us that all three systems work together when we exercise—they are dependent upon each other.  For example, the skeleton-muscular system works to move the muscles and skeleton.  In order for muscles to contract they require oxygen and nutrients.  The cardiovascular system and respiratory system work to provide the muscles with both.  The harder the muscles work, the more oxygen and nutrients are needed and the harder the cardiovascular and respiratory systems work to provide both.

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B. Explain that in Investigation Four, students will continue to investigate exercise by exploring how exercise relates to diet, energy input, energy output, and energy balance.

1. Instruct students to look at the terms basal metabolic rate, energy input, and energy output in their Scientist’s Glossary.  

Ask the following questions as a method of narrowing the student’s focus on the concept that energy balance and health are closely related.  These questions are designed to prepare the students for the Investigation to follow.

a. Ask students: Based on these definitions of terms, which term do you think best describes the process of digestion? Energy input.

b. Ask students: How does energy get into the body? Through the food we eat.

c. Ask students: What do you think energy output is? Student answers will vary, but should center on the concept that it is energy used by the body as fuel.

d. Ask for a show of hands:  How many students play sports or participate in other physical activities like dancing or hiking? Is this energy input or output? These are example of energy output.

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2. Ask students:  How do you feel after one of these activities? Student answers will vary, but should include the following:  tired, out of breath, sweaty, heart beating faster.  

Listen for someone to mention hunger.  If it is not mentioned, follow up by asking: Does exercise make you hungry?

3. Ask students:  Why do you think exercise makes you hungry? Student answers will vary.  

Tell students that they will be exploring the relationship between hunger and exercise during Investigation Four and that they should keep this question in mind as they conduct their experiments.

4. Ask students:  What other times of the day do you usually feel hungry? Student answers may vary, but are likely to include:  after school, meal times, when they wake up, between meals, etc.

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5. Remind students that we do not exercise when we sleep.  

Ask students:  Why do you think you are hungry when you wake up in the morning if you have not been exercising? Student answers will vary.

Sometimes we think we are not using energy when we are asleep. However, this is far from true. We burn energy when we expand and contract our chest muscles and diaphragm with every breath. Our heart beats all night while we are sleeping. Our body temperature is kept warm by burning food energy as we sleep. Even our brain requires a lot of energy as we sleep and dream!

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C. Divide students into pairs and explain they will perform an activity to help them answer this question. Direct one student to sit and observe while the other student jogs in place for 30 seconds. Have students switch roles and repeat the exercise.

1. Ask the students to make two lists based on their observations:  one for the actions of the observer, and one for the actions of the jogger (see slide).

2. Ask students: What type of energy was used in performing the two activities, input or output? Energy output was used.

3. Explain that actions can be voluntary (require thought to perform) or involuntary (the body performs them automatically).  Ask the students to study the list from the previous question and the chart. Guide the class in comparing and contrasting the activities of the jogger and the activities of the observer by asking the following questions:

a. Ask students: Is jogging classified as an involuntary action or a voluntary action? Why? Voluntary, because it requires thought to start and stop.

b. Ask students: Were all the actions you noticed in the observer voluntary or involuntary? Student answers will vary.  

NOTE:  Any actions which do not require active thought, such as the sample entry “muscles contracting to hold sitting position”, are involuntary because the student who is sitting is not thinking about which muscles to contract and which muscles to relax to maintain the sitting position.  If, however, the students simply say “sitting”, that would be voluntary because it takes into account the decision to continue sitting—in other words, conscious thought is involved.  Breathing and blinking can be voluntary when done on purpose—for example, holding one’s breath or batting one’s eyelids, but in the context of the sample table above those actions are occurring because the part of the brain responsible for involuntary maintenance actions is directing those activities.

c. Ask students: Were all the actions you noticed in the jogger voluntary or involuntary?  Student answers will vary.  

NOTE:  Any actions which do not require active thought, such as the sample entry “muscles contracting to lift legs”, are involuntary because the student who is sitting is not thinking about which muscles to contract and which muscles to relax to lift and lower the legs.  If, however, the students simply say “jogging”, that would be voluntary because it takes into account the decision to continue jogging—in other words, conscious thought is involved.  Breathing and blinking can be voluntary when done on purpose—for example, holding one’s breath or batting one’s eyelids, but in the context of the sample table above those actions are occurring because the part of the brain responsible for involuntary maintenance actions is directing those activities.

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4. Explain that some of the involuntary actions, such as breathing and circulation, the students observed and listed can be described as maintenance functions because they are functions the body needs to survive.  The energy used for these functions is called basal metabolic rate.

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5. Ask students: Based on what you just learned, why do you think food is important? Food provides the fuel (nutrients) we need to survive.  The body breaks nutrients down into their simplest forms and uses them to build and repair cells and to provide the body with energy to function.

6. Ask students: Can you recall the six classes of nutrients and give an example of a food rich in that nutrient?

Water—beverages, high-moisture fruits and vegetables, milk

Carbohydrates—sugar, honey, cereals, pasta, grains, breads

Protein—meats, legumes (beans, alfalfa sprouts, peanuts), nuts

Fats—butter, fatty meats, margarine, cooking oils

Vitamins—fruits, vegetables, grains

Minerals—meats, dairy products, dark leafy greens (turnip, beet, chard, kale, mustard, spinach), fruits

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D. Ask students the following question as a way of reviewing the relationship between food, digestion, and the digestive system:  How do nutrients get into the body?

1. Bring the students back together as a class and ask them to share their Mind Movies. After each group has described their sequence of events, direct students’ attention to the digestive system sequence in the Scientific Background of the Student Data Record.

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2. Briefly review the information below with the students and encourage students to compare the pathway they described in their Mind Movie to that in their Student Data Record. Students should diagram the path food takes as it is digested by drawing arrows to the appropriate organ on the picture as they fill in the terms during the discussion.

a. Mouth:  contains the teeth, tongue and salivary glands.  The tongue mixes the food with saliva to moisten it and starts carbohydrate digestion as teeth grind the food into smaller particles.

b. Throat:  the junction between the mouth and the esophagus.  The tongue moves the food to the throat where it is swallowed.  The scientific term for the throat is pharynx.

c. Esophagus:  the muscular tube connecting the throat with the stomach.  Muscles in the esophagus contract rhythmically to move the food from the throat to the stomach.

d. Stomach:  food enters the stomach and is mixed with acid and the first protein-digesting enzyme (pepsin).  The stomach releases food into the small intestine in small increments.

e. Small intestine:  the major site of food digestion and nutrient absorption. Food is constantly mixed and remixed with enzymes from the pancreas and emulsifiers (substances that break down fats) from the liver.  The nutrients are then absorbed by the villi (fingerlike projections) lining the small intestine and pass into the bloodstream to be carried to the rest of the body’s tissues.

f. Large intestine:  undigested food from the small intestine enters this organ for final processing.  Water and any remaining water-soluble vitamins and minerals are absorbed here.  The remaining undigested food is excreted as feces, or waste.

3. Briefly revisit students’ Mind Movies.  Ask students to close their eyes.  Call on students to describe where they are.  Are they in the throat?  Are they in the stomach?  What is happening there?

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E. Conclude this part of the Investigation by directing students’ attention to the term energy balance in the Scientist’s Glossary.

1. Explain that energy balance is the term used to explain the relationship between a person’s energy input and his or her energy output, and can be calculated mathematically because energy input and output can be measured.

a. Ask students: How do you think we measure energy input? Student answers will vary, but should focus on the idea that we can measure the energy content of the foods we eat and calculate a person’s energy input based on what they consume.

b. Ask students: How do you think we measure energy output? Student answers will vary.  Explain to students that scientists use special equipment to measure oxygen used and carbon dioxide produced during different activities and can use formulas based on these values to calculate energy output for the activities.

2. Explain that students will study the factors that affect a person’s energy balance in Investigation Four.  As they conduct their experiments, they should consider the following question:

How do you think the types of activities a person performs influence his or her energy balance?

a. Remind students that food is a source of energy.  Ask students:  How do you think food choices influence energy balance? This is what students will explore in lab.