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SOURCE Lesson Plans Detail
Țħě Ŀǿǿp đě Ŀǿǿpș įň ǿųř Bǿđỳ
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
Icebreaker
Lecture with worksheet
"Doctoring"
Quick review
Lab exercise
Procedure
Underlined terms appear on the supplemental worksheet ­ students should be filling out important definitions and concepts as the lesson progresses.
1. Icebreaker
2. Introduction
a. What is your normal body temperature?
b. When you're cold how does your body respond?
c. What about when you're warm?
d. What happens to your heart rate when you're exercising?
e. 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
a. Ask the kids what they think the difference is
b. Emphasize that positive/negative feedback does not necessarily a good/bad outcome
c. 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
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d. 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)
a. Define the endocrine system and its function
b. Loop #1 - Maintenance of blood sugar using insulin and glucagon
i. Go over hormones and their function and secretion/target location on the worksheet
ii. Write loop on board
iii. Is this an example of positive or negative feedback?
c. Loop #2 - Hunger
i. Go over function of ghrelin and leptin on the worksheet
ii. How is this an example of maintaining homeostasis?
iii. What is the "controlled variable" that the body is trying to maintain?
d. Loop #3 - Oxytocin release during childbirth
i. Write loop on board
ii. Go over function of hormones important for childbirth on chart
iii. Is this an example of positive or negative feedback? Positive.
e. Loop #4 - Growth
i. 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)
ii. Feedback: the somatomedins inhibit the release of GHRF from the hypothalamus
iii. Positive or negative feedback?
iv. "Doctoring"
i. A patient comes to you who has very short stature
ii. What hormone do you test for? Growth hormone.
iii. After the test, you find that the patient does have sufficient growth hormone in their bloodstream.
iv. What do you test for next (what's next in the loop)? Somatomedins.
v. After the test, you find that the patient has somatomedins in their bloodstream as well.
vi. What could you test for next? Receptors.
vii. Where? Bones, muscles, connective tissue.
viii. The receptors are missing or there aren't enough!
ix. Unless the receptor is there, the hormone cannot react with the target organ. This scenario is a case of Loran's Dwarfism.
x. 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
a. Positive: movie popularity, drug addiction (positive doesn't mean it's a good thing!), hurricane formation
b. Negative: springs, predator-prey population
8. LAB - Effects of exercise on homeostasis
a. 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
b. Take resting measurements
c. Have the student jump rope consecutively for ten minutes; take measurements every two minutes
d. Have students describe the difference in qualitative and quantitative measurements
e. Graph the quantitative measurements
f. 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
https://www.brown.edu/academics/science-center/outreach/stem_orc/lessons/detail/a959e36b-4f21-a2e4-e9b2-ab6de2ccb0fe
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Supporting Web Information
http://www.hormone.org/Endo101/page3.cfm
http://biology.clc.uc.edu/courses/bio105/endocrin.htm
Reference(s)
http://www.mhhe.com/biosci/ap/holehaap/student/olc2/graphics/shier04ap_s/ch13/chapt13.pdf.
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
QTY
UNIT
ITEM
5
Each
Yeast
5
Each
Yeast
5
Each
Yeast
5
Each
Yeast
Alignment Info
Audience(s)
High school students
STEM
Biology
Area(s)
Standard(s)
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
Hands-on
Type(s)
Grade
High School
Level(s)
Version
2
Created
11/11/2012 02:10 PM
Updated
11/13/2012 11:23 PM
Břǿẅň Ųňįvěřșįțỳ
Providence, Rhode Island 02912, USA
Phone: 401-863-1000
© 2016 Brown University
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