Engage
Show students National Geographic’s “Weird But True” fun facts on the human body. http://kids.nationalgeographic.com/explore/adventure_pass/weird-but-true/humanbody2/#WBT2_180.png
Think/Pair/Share
What do you know about the human body? Do you know any fun facts? Give the students a few minutes to discuss with their partner and then share aloud.
Explore
Ask for a volunteer to come to sit in a chair facing the class with her back to you. Stand behind the student and clap your hands loudly. More than likely, the student will jump. Ask the class: Why did she jump when I clapped? Explain to the students that what they just witnessed was a case of feedback in action. Feedback is the process in which our brains take in information and then use it to send information back to different parts of our bodies that control our actions. Ask the class: What system in our bodies sends messages back and forth from the brain? (the nervous system)
Explain that the nervous system is made up of two parts—the voluntary nervous system is the part that we can control and the involuntary nervous system is the part that simply happens inside us all the time. The involuntary part of our nervous system uses feedback to keep our bodies functioning properly, and most of the time we don’t even know it is going on. Think/Pair/Share different functions our body performs that are a part of our involuntary nervous system. (heart beating, breathing, etc.) Discuss how breathing is part of the involuntary nervous system. Sensors in your body constantly monitor the level of carbon dioxide and oxygen in your blood, sending information to the brain. If the oxygen level drops compared to the amount of carbon dioxide, the brain sends a message to the heart to start pumping faster so that your breathing rate increases. This happens when you start exercising. Once the levels of oxygen in the blood come back to normal, the brain tells your heart to slow down and your breathing rate drops.
Toss a rubber ball to a student volunteer. Ask the class: How did he know when and where to catch the ball? (His eyes sent a message to his brain, and the brain sent a message to the hands to move to the correct spot.) Was this a voluntary or involuntary response? (voluntary) He didn’t have to catch the ball but chose to make the catch. He used feedback to make this happen.
Give each group of students a ruler. The students will be testing their reaction times using the ruler. One person will hold the ruler at the top while the other partner places his or her hands at the bottom of the ruler without touching it. The person holding the ruler by the top will drop the ruler saying when he is dropping it. The person taking the test will try to catch the ruler when it begins to fall by clapping his hands together. He will record where he grabbed the ruler on a chart like the one below in his notebook. The lower the number, the faster the reaction time. The students will repeat these steps on one another for 10 trials each.
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Reaction Time Data Chart
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Trial 1
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Trial 2
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Trial 3
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Trial 4
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Trial 5
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Trial 6
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Trial 7
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Trial 8
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Trial 9
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Trial 10
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Explain
Students can answer the following questions in their notebooks and then use them in a class discussion.
- Based on your data, did your reaction time change over the 10 trials? How so?
- Is reaction time a voluntary or involuntary response? Explain.
- Explain how feedback helped you catch the ruler. What steps had to happen in order for your hand to react in time to catch the ruler?
Elaborate
Ask the students to test how their sense of balance is impacted by spinning around a few times. Put a 3-feet long piece of masking tape on the ground in a straight line. Have the students line up at one end and walk the line. Have them do it again but slowly spin around a few times before walking. Discuss how even though most feedback systems in our bodies are designed to adjust to changing conditions, they don’t always work as well as you might want them to.
Evaluate
The student responses on to the discussion questions in their notebooks can be used as a formative assessment. Teacher observation should be ongoing throughout the lesson.
