Engage: Take a Deep Breath!

Have you ever held your breath? When you hold your breath until you can't hold it anymore, what is the first thing you do, inhale or exhale? Try it a few times. What did you find out? Click here to read a blog regarding the ins and outs of respiration.

Let's take what you've learned about the concept of internal management and focus on other body processes. Are they managed similar to the way carbon dioxide is managed? If not, then how are they managed? What systems are in place?

To investigate further, prepare to do a series of brief experiments described in the Explore section. Use a science notebook or journal to describe the procedures and record your observations.

Explore: Evidence of Systems in Place

Investigations 1 - 3 may be done individually or with a partner; however, Investigation 4, will require a partner. Think of the following questions as you proceed.

  • What is homeostasis?
  • How does your body respond when you push the boundaries?
  • How do your systems know how to adjust to the conditions your body experiences?


Record your observations and explanations in your science notebook or journal. 

Investigations Materials Procedures Results

1. Heart Rate

Does your heart rate vary over a 15-minute time frame? Why or why not?

Timer or watch with a second hand • While seated, take your pulse for 15 seconds.
• Multiply the number of beats by 4 to measure beats per minute.
• Record the data.
• Repeat the procedure every minute over a 15-minute time frame.
Graph the data and explain your results.

2–3 Combo

2. Heart Rate Pace

Does your heart rate increase or stay the same for every 20 jumping jacks jumped? Why?

3. Thermoregulation

When do you start sweating? Why?

Timer or watch with a second hand • Record your resting heart rate following the instructions in Investigation 1.
• In a cleared area, stand up, and do 20 jumping jacks. Are you sweating yet?
• Stop, and take your pulse for 15 seconds.
• Calculate and record your heart rate as beats per minute.
• Record the time when you start sweating.
• Repeat the steps for a total of five sets.
• Record the amount of time it takes for your pulse rate to return to normal.
Graph the data and explain your results.

2–4 Optional Combo

4. Respiration Race

Does your respiration rate increase at the same rate as your pulse when you exercise? Why or why not?

Timer or watch with a second hand Note: Implement the following procedure simultaneously with the procedures from Investigation 2. You'll need a partner to track the respiration data.
• While sitting, record the number of times you complete an inhale/exhale cycle over a 1-minute time period.
• Each time you stop to count your pulse, have your partner count the number of respirations.
Graph the data and explain your results.


Explain: How It Works

Watch the following video to better understand how homeostasis is managed in your body through positive and negative feedback loops.

Khan Academy via YouTube; retrieved from http://youtu.be/zv8LHyH7_rI

Elaborate: Control Central

You have had a chance to investigate how your pulse/heart rate, respiration rate, and thermoregulatory mechanisms respond during exercise. The nervous and endocrine systems work together with other systems such as the circulatory and integumentary systems to keep your internal environment in a state of homeostasis. What if you had to overtly manage your internal environment to keep it in balance? Click the image below to engage in an activity that helps answer the previous question.

Note: This image opens a window in a new tab. When you are finished with the activity, close the tab and return to the lesson.


Cite Source
Activity image and link courtesy of Houston Public Media/PBS LearningMedia; retrieved from http://houstonpbs.pbslearningmedia.org

How did you do as the person in charge of homeostasis? Were you able to successfully adjust the system levels according to the feedback? Watch the following video to reinforce the functionality and importance of internal feedback systems.

MIT Open Courseware; retrieved from http://video.mit.edu/watch/concept-vignettes-feedback-loops-27052/

Teacher Notes

This resource is intended to support Tier 1 classroom instruction. The lesson focus is Texas Essential Knowledge and Skills B(11)(A), which states that the student is expected to describe the role of internal feedback mechanisms in the maintenance of homeostasis. As with most instructional materials, it is up to the teacher to know how to integrate the resource into instruction in a way that best meets the learning needs of the students.

This resource is formatted using the 5 E lesson model. However, it is not intended to be a complete 5 E lesson. As the instructional designer, you may want to include additional components, such as formative and summative assessments, discussion questions, or additional projects that help students further explore supporting concepts. The following is a brief description of each section so that you can plan accordingly.

Engage: Take a Deep Breath!

Students answer the following question: "When you hold your breath until you can't hold it anymore, what is the first thing you do, inhale or exhale?" After they answer the question, they read a blog that explains how the body tracks the amount of carbon dioxide, a waste product of cellular respiration, in the blood. The Engage sets up the investigations in the Explore.

Explore: Evidence of Systems in Place

In this section, there are several investigations for students to perform individually or in groups of two. Students must answer questions about changes in pulse and respiratory rates as well as thermoregulation. The materials are minimal but the students must create their own data tables and graphs. As an option, students may change the parameters of the investigations as long as they are able to record valid data and draw conclusions that help them describe the role of feedback systems.

Explain: How It Works

Students watch a video that explains positive and negative feedback systems. It might be a great time to reexamine data from the investigations in the Explore in case students need to revamp their explanations.

Elaborate: Control Central

Students are given a chance to act as a systems controller in order to maintain the homeostatic levels of a virtual person. This interactive is probably best utilized under conditions where each student has his or her own digital device on which to play. Consider assigning the activity as homework if you are not able to schedule time in a computer lab. The last activity is a film that provides scientific vocabulary and interactive checkpoints for the learner.

Be sure to View Related Items at the bottom of the screen for additional resources, videos, and links. These can be used to differentiate instruction for a variety of learners.