SOURCE Lesson Plans Detail

The Loop de Loops in our Body

Topic Feedback Systems
Program Brown Science Prep
Developed by Deepa Chellappa
Developer Type Brown students

Overview / Purpose / Essential Questions

What is a feedback loop? What is homeostasis? How does the body work to maintain homeostasis?

Performance / Lesson Objective(s)

Students will be able to:

  • Explain the difference between positive and negative feedback loops
  • Describe several feedback loops in the human body and the hormones involved
  • Explain the difference between qualitative and quantitative observations

Lesson Materials

Worksheets, jump ropes, heart rate monitors, blood pressure monitors, thermometers

Lesson Motivation

The endocrine system in the human body can be used as a model to show the importance of homeostasis and feedback loops for a number of systems in biology, physics, chemistry and in nature.

Lesson Activities


Lecture with worksheet
Quick review
Lab exercise


Underlined terms appear on the supplemental worksheet - students should be filling out important definitions and concepts as the lesson progresses.
  1. Icebreaker
  2. Introduction
    1. What is your normal body temperature?
    2. When you're cold how does your body respond?
    3. What about when you're warm?
    4. What happens to your heart rate when you're exercising?
    5. What happens when you're hungry?
  3. Homeostasis - break down both parts of the word before providing the full definition
  4. Feedback loop - how are homeostasis and feedback loops related?
  5. The difference between positive and negative feedback loops
    1. Ask the kids what they think the difference is
    2. Emphasize that positive/negative feedback does not necessarily a good/bad outcome
    3. Count the number of pluses and minuses in the system; if the overall number of minuses is odd, it is a negative feedback loop because the effect is to decrease the stimulus
    4. This is a key point in the lesson so spend as much time as necessary to make sure students understand the difference
  6. Basic anatomy of the endocrine system in the human body (use accompanying worksheet to label important glands and organs as well as identify important hormones and their functions)
    1. Define the endocrine system and its function
    2. Loop #1 - Maintenance of blood sugar using insulin and glucagon
      1. Go over hormones and their function and secretion/target location on the worksheet
      2. Write loop on board
      3. Is this an example of positive or negative feedback?
    3. Loop #2 - Hunger
      1. Go over function of ghrelin and leptin on the worksheet
      2. How is this an example of maintaining homeostasis?
      3. What is the "controlled variable" that the body is trying to maintain?
    4. Loop #3 - Oxytocin release during childbirth
      1. Write loop on board
      2. Go over function of hormones important for childbirth on chart
      3. Is this an example of positive or negative feedback? Positive.
    5. Loop #4 - Growth
      1. Go over loop (hypothalamus releases GHRF which causes release of GH from the anterior pituitary, which causes secretion of somatomedins from the liver which affect receptors on bones, muscles and connective tissue)
      2. Feedback: the somatomedins inhibit the release of GHRF from the hypothalamus
      3. Positive or negative feedback?
      4. "Doctoring"
        1. A patient comes to you who has very short stature
        2. What hormone do you test for? Growth hormone.
        3. After the test, you find that the patient does have sufficient growth hormone in their bloodstream.
        4. What do you test for next (what's next in the loop)? Somatomedins.
        5. After the test, you find that the patient has somatomedins in their bloodstream as well.
        6. What could you test for next? Receptors.
        7. Where? Bones, muscles, connective tissue.
        8. The receptors are missing or there aren't enough!
        9. Unless the receptor is there, the hormone cannot react with the target organ. This scenario is a case of Loran's Dwarfism.
        10. Could the patient be treated with hormone therapy? No. Since we already know the patient has sufficient hormones, additional GH wouldn't help - they need more receptors to be able to affect their bones and muscles.
  7. Other feedback loops
    1. Positive: movie popularity, drug addiction (positive doesn't mean it's a good thing!), hurricane formation
    2. Negative: springs, predator-prey population
  8. LAB - Effects of exercise on homeostasis
    1. One student is the guinea pig who does exercise; one student measures blood pressure; one student measures heart rate; one student measures body temperature; one student looks at changes in sweating, breathing rate and change in skin color; one student is the recorder
    2. Take resting measurements
    3. Have the student jump rope consecutively for ten minutes; take measurements every two minutes
    4. Have students describe the difference in qualitative and quantitative measurements
    5. Graph the quantitative measurements
    6. What changes occurred? Why do these changes happen in our bodies during exercise?

Wrap up / Conclusion

Quick review (identify the following as positive or negative feedback):

  • Tries to maintain homeostasis
  • Continually disrupts homeostasis
  • Inhibits hormones
  • Continues to strengthen the stimulus
  • Used when oxytocin is released to intensify contractions during childbirth
  • Used when kidneys remove hydrogen ions from the blood when pH becomes too acidic

Follow up

Next lesson: begin with tossing around a ball and describing the steps in the insulin/glucagon feedback loop

Supporting Web Information


Pre Assessment Plan

Question: What is homeostasis?

Show some data involving the target of a GH's levels in the body and the levels of GH itself after some time and ask the students what is going on.

Post Assessment Plan

Show the same data and ask whether it's a positive or negative feedback loop. What loop that we studied does this look like?

Supplies List


Alignment Info

Audience(s) High school students
STEM Area(s) Biology
Life Sciences (RI GSE) LS4.9-11.10a
Students demonstrate an understanding of human body systems by … explaining how the roles of the immune, endocrine, and nervous systems work together to maintain homeostasis.
Life Sciences (RI GSE) LS4.9-11.10b
Students demonstrate an understanding of human body systems by … investigating the factors that affect homeostasis (e.g. positive and negative feedback).
Activity Type(s) Hands-on
Grade Level(s) High School
Version 2
Created 11/11/2012 02:10 PM
Updated 11/13/2012 11:23 PM