1 Food For Thought: What fuels us? Glucose, the endocrine system, and health Lesson 2: How are glucose levels regulated ...
Food For Thought: What fuels us? Glucose, the endocrine system, and health
Lesson 2: How are glucose levels regulated in the body? I. Overview The purpose of this lesson is to introduce the endocrine system and its role in maintaining blood glucose homeostasis in the body. Students model the endocrine system by participating in a system that makes cheese and crackers. Students then watch a video explaining the fundamental aspects of the endocrine system. Afterwards, students discuss what parts of their cracker and cheese production system represented specific aspects of the endocrine system. To further relate the lesson to glucose homeostasis, students develop a model for the action of glucagon and insulin in the body by organizing cards that represent different organs, hormones, receptors, and intracellular molecules.
Connections to the driving question In this lesson students learn about the endocrine system and how it is able to control glucose levels in the blood. At the end of the lesson students will generate a model of the insulin and glucagon and their actions on the body to maintain blood glucose availability during eating and fasting.
Connections to previous lessons In Lesson 1, students were introduced to the body’s main energy source – glucose. Students determined that certain organs need glucose more than others and also learned that glucose is distributed differently depending on the current needs of the body. In this lesson, students explore how this occurs. Students learn that the endocrine system is responsible for many of the mechanisms by which glucose availability is achieved and how glucose levels are regulated.
II. Standards National Science Education Standards 12CLS5.4 The complexity and organization of organisms accommodates the need for obtaining, transforming, transporting, releasing, and eliminating the matter and energy used to sustain the organism. 12CLS6.2 Organisms have behavioral responses to internal changes and to external stimuli. Responses to external stimuli can result from interactions with the organism's own species and others, as well as environmental changes; these responses whether can be innate or learned. The broad patterns of behavior exhibited by animals have evolved to ensure reproductive success. Animals often live in unpredictable environments, and so their behavior must be flexible enough to deal with uncertainty and change. Plants also respond to stimuli.
Benchmarks for Science Literacy The Human Organism: Basic Functions Communications between cells is required to coordinate their diverse activities. Cells may secrete molecules that spread locally to nearby cells or that are carried in the bloodstream to cells throughout the body. Nerve cells transmit electrochemical signals that carry information much more rapidly than is possible by diffusion or blood flow. 6C/H3 Common Themes: Systems The successful operation of a designed system often involves feedback. Such feedback can be used to encourage what is going on in a system, discourage it, or reduce its discrepancy from some desired value. The stability of a system can be greater when it includes appropriate feedback mechanisms. 11A/H3 Common Themes: Constancy and Change If a system in equilibrium is disturbed, it may return to a very similar state of equilibrium, or it may undergo a radical change until the system achieves a new state of equilibrium with very different conditions, or it may fail to achieve any type of equilibrium. 11C/H1
III. Learning Objectives Learning Objective Identify the six fundamental components of the endocrine system
Assessment Criteria Students can identify the following components of the endocrine system: 1. A gland that detects a change in the environment 2. In response to the change, a hormone is secreted by the gland 3. Hormones travel through the blood to the target organ 4. Target organ has specific receptors that will bind the hormone 5. Hormone binding elicits a cellular response 6. Negative feedback loop - the end result produced by the cell inhibits further release of the hormone.
Associated Materials: U7_L2_EndocrineDiagram_Blank
Location in Lesson Activities 1 - 4
Explain how insulin and glucagon work in the body to maintain homeostasis.
Students develop blood glucose homeostasis models on whiteboards. Using their model, each group should be able to explain the following:
Activity 3 & 4
Insulin and glucagon are the two hormones that work together to maintain blood glucose level homeostasis. In response to high blood glucose, insulin will be released from the pancreas and bind to receptors on muscle and liver cells to trigger uptake of glucose into the cells. This excess glucose will be stored as glycogen. In response to low blood glucose, the pancreas will release glucagon. Glucagon travels through the blood and binds to receptors on the muscle and liver cells. Glucagon triggers the breakdown of glycogen in cells and the subsequent release of glucose into the blood. Using their model, students explain how disruptions to the blood glucose homeostatic system can lead to various medical conditions.
Associated Materials: U7_L2_StudentSheet_Homeostasis Explain how biological processes are regulated by negative feedback.
Using their blood glucose homeostasis models, students should be able to explain the following:
Negative feedback mechanisms keep blood glucose levels within a specific range. In high blood glucose conditions, the release of insulin and subsequent decrease in blood glucose levels triggers the pancreas to stop releasing insulin. In low glucose conditions, the release of glucagon and subsequent increase in blood glucose levels triggers the pancreas to stop releasing glucagon. Disruption of this negative feedback loop can lead to illness and/or disease.
Associated Materials: U7_L2_EndocrineDiagram_Blank U7_L2_StudentSheet_Homeostasis
IV. Adaptations/Accommodations Safety Double check if students have any allergies to cheese (lactose intolerance). Since some students will be handling food for the whole classroom, please make sure all students have washed their hands before handling the food.
V. Timeframe for lesson
Opening: 5 minutes Activity 1 – Cracker Activity: 20 minutes Activity 2 – Video and Discussion: 20 minutes Activity 3 – Insulin and Glucagon Models: 30 minutes Activity 4 – Medical Scenarios: 20 minutes
VI. Advance prep and materials Activity 1: Cracker Activity Materials: Box of Crackers Cheese (Kraft Singles) or Cream Cheese Paper Towels Drinks and cups U7_L2_Instructions_CrackerActivity U7_L2_EndocrineDiagram_Blank U7_L2_EndocrineDiagram_ANSWERS (for teacher use) Preparation: Have food available and set up at specific stations in the classroom. Different foods can be chosen. However, make sure that the food can be assembled. (Any type of spread on a biscuit, cracker, or cookie works well). Have all students wash their hands thoroughly with warm water and soap. Print out a copy of U7_L2_Instructions_CrackerActivity and cut the paper into separate sections (one for Group X, one for Group A, and one for Group B) so the instructions can be given to each group. Print out copies of U7_L2_EndocrineDiagram_Blank for every student. Have U7_L2_EndocrineDiagram_ANSWERS available for teacher use.
Activity 2: Video and Discussion Materials: Video – The Endocrine System o Accessed at http://neuron.illinois.edu/videos/video-the-endocrine-system OR https://www.youtube.com/watch?v=tN78hYn3ehc
Activity 3: Insulin/Glucagon Models Materials: U7_L2_Resource_CheckoutAnalogy U7_L2_Cards_GlucoseModel_Organs U7_L2_Cards_GlucoseModel_Molecules Poster board and markers or whiteboard and dry erase markers. Preparation: Print and cut out U7_L2_Cards_GlucoseModel_Organs and U7_L2_Cards_GlucoseModel_Molecules to create one set of cards. Each group in the lesson will get one set of cards. For repeated use the documents can be laminated and the cards cut out (This takes a while). Read through U7_L2_Resource_CheckoutAnalogy so this concept can be explained to the students during class. The information in this document is also provided at the end of this lesson plan.
Activity 4 (Conclusion): Scenarios of Insulin/Glucagon Models Materials: U7_L2_Cards_GlucoseModel_Scenarios U7_L2_Cards_GlucoseModel_Scenarios_ANSWERS Preparation: Print one copy of U7_L2_Cards_GlucoseModel_Scenarios. Cut the sheet so that there is one scenario on each piece of paper. Reference the answer key if needed.
Homework and Assessments Materials: U7_L2_Assessment_Homeostasis U7_L2_Assessment_Graphs (Optional) U7_L2_Assessment_Graphs_ANSWERS (Optional)
VII. Lesson Implementation Teacher Pedagogical Content Knowledge: It is helpful to choose a limited amount of vocabulary words to be the focus of a unit. In this way students gain an in-depth understanding of the important terms that emphasize the main ideas of the unit. The main vocabulary words should be brought up frequently throughout a unit. For this unit, the main vocabulary words are: (Words in bold introduced in Lesson 2). Homeostasis Negative Feedback Insulin vs. Glucagon Fight-or-Flight Response
Opening of Lesson: Remind students of what they learned the previous day. Glucose is the body’s main energy source and glucose levels can change due to certain circumstances (i.e., exercising) Start the lesson by presenting the driving question, verbally and visually, to the class: The body is able to change glucose allocation depending on the circumstances, but how? How do organs and tissues communicate? How are glucose levels regulated in the body? Take this time to hear students’ thoughts on this topic. Students may suggest that nerves allow the body to communicate. Although this is true, there is another way the body is able to communicate that will be the main focus of this unit: the endocrine system. The endocrine system is a system in the body that sends chemical messages to the body to perform certain functions. These functions include:
Growth and Development: growth hormone, testosterone, estrogens Homeostasis: Insulin, glucagon, thyroid hormone Response to Stimuli: adrenalin
It is important to highlight these three points because the lesson will mainly focus on the endocrine system’s role in homeostasis. However, students should be aware of the broad range of endocrine functions.
Main Part of Lesson
Activity 1: Cracker Activity Tell students that, as a class, they will be modeling homeostasis in the body. Put 3 students in “Group X”, 3 students in “Group A”, and 3 students in “Group B”. The rest of the students are body cells and
should be at their desks. Tell the students (in Groups A and B particularly) that before starting the activity they need to thoroughly wash their hands with warm water and soap. Inform students that they will be modeling important parts of the endocrine system. Make sure that group X is far away from Groups A and B; this is to help illustrate that hormones can travel throughout the body. Once groups have been formed and situated, pass out the pre-cut instructions from U7_L2_Instructions_CrackerActivity to the respective groups. Have the groups read their roles. Before starting the activity, check with each of the three groups to make sure they understand what the instructions ask of them. Begin the Activity: Although different students have unique roles in the system, make sure the entire class is aware of what is occurring at each step. It is best that the students do not rush through their roles. The entire class should be able to observe this activity. Step in Activity
Relation to Endocrine System
First, the teacher announces, “I sense this class needs energy!“
This represents a gland sensing a change in the environment.
The teacher sends half of the students from Group X stating, “We are hungry. Go forth and send the signal.” Group X will walk across the room to group Groups A and B. The teacher will continue to send members of Group X forth until he/she has received both drinks and food. (As the teacher, make sure to send at least two signals before receiving this negative feedback).
This represents the gland releasing a hormone into the bloodstream to be transported throughout the body.
Members of Group X will give Groups A and B high fives. Only one high five can be given by each member of Group X.
This represents a hormone binding to a receptor as well as receptor specificity.
Once the “receptors” on Groups A and B have received a high five, they will bring 10 cups or 10 crackers to the rest of the members in their cell.
This represents receptors initiating change in cell in response to the hormone.
Upon receiving Group X’s signal, Groups A and B will begin to make snacks or drinks. Each member of Groups A and B can only make food that is presented in front of them by the receptors. In order to make more they will have to wait for another signal.
Groups A and B represent the signal changes that occur inside of the cell as a result of the hormone binding to the receptor.
Members of Groups A and B will bring either drink or food to the other students and the teacher. The teacher should eat the cracker and announce to the class, “Mmm, the class has
This represents a negative feedback loop. The end result that the gland was trying to achieve for the body (a snack)
received energy, I will stop sending Group X forth to signal to Groups A and B.”
acts as a signal to inhibit the release of hormones from the gland.
It is IMPORTANT that the teacher makes sure to “send another signal” before Groups A and B deliver the drink and crackers to the teacher. Say something like, “I still sense low energy levels in this class, go forth and send the signal (to the remaining members of Group X)”
This helps illustrate that the master gland will continue to secrete hormones until its feedback signal halts the hormonal release.
After the model has been acted out, run through what happened at each step (only in the left column above) with the students so they grasp what is occurring at each step. Finally ask: Was homeostasis achieved? Why do you think the teacher sent members from Group X multiple times? What system did we just mimic in the body?
Scientific Practices: Developing and Using Models In this activity, students learn about the Endocrine System by comparing the actual model of the endocrine system to the analogy of the cracker activity. In further activities, students will continue to construct and use models. As students’ understanding of the endocrine system deepens, their models become more complex, drawing upon aspects of their previous models. This process will allow students to build and strengthen their mental models of this system.
Activity 2: Endocrine Video and Discussion Before the video, hand out U7_L2_EndocrineDiagram_Blank. Students will complete this sheet after watching the video and during class discussion. This document should be used as a resource for students throughout the unit, and as a study tool for any summative assessment. Allow students to enjoy their snack while they view Video: The Endocrine System via the Project NEURON website or YouTube at: http://www.youtube.com/watch?v=tN78hYn3ehc. This video explains how the endocrine system is important in maintaining homeostasis, particularly for glucose. The video models the fundamental aspects of the endocrine system that can be applied to all hormones. These main concepts include (1) a gland detecting a change in the environment, (2) hormone secretion by gland, (3) blood borne hormones, (4) receptor specificity, (5) cell response, and (6) negative feedback loops. After the video, guide discussion with the students on what parts of the cracker-cheese system modeled certain points of homeostasis regulated by the endocrine system. If you want, have students come up
to the front of the room and draw models on the board to support discussion and understanding amongst the entire class. Some example guiding questions for this discussion could include:
What was the gland in our cracker activity? o The teacher was the gland. The teacher sensed the environment; that is he/she realized the class needed a snack. Then, the teacher sent out hormones as a message to the rest of the class.
Which group were hormones? o Group X members were the hormones. They were sent by the teacher and traveled to Groups A and B. They were receptor specific because they were only able to send a signal through a high five!
Which group were the receptors? o The members of Groups A and B were receptors. They bound to the “hormones.” Then they initiated a cell response by bringing the cups or crackers to the rest of the members in their cell.
Let’s say there is a third cell called Cell C. Cell C is responsible for cleaning the classroom after a meal. Cell C only responds to handshakes. Based on the video, would Cell C students respond to the hormones that were sent out in our example? o No. The video said that hormones are receptor specific. Our hormone gives high fives and Cell C only responds to handshakes. They would not be able to communicate with one another. (Feel free to replay the section of the video of a hormone bouncing off a different receptor before binding to its receptor on the target cell [1:23-1:39])
Did the hormones/Group X have an effect on the “cells” they bound to? o Yes. The initiation of signaling from the “receptors” caused members from Cells A and B to make food for the entire class. The cell responded when the hormone bound to the receptor.
Was there a negative feedback system like the video in the class model? o Yes! When the teacher ate the cracker he/she realized that the goal had been achieved and stopped sending group X forth.
Was the food just for the gland? o No the food was for the entire class (i.e. the entire body). The gland just responded to the food with negative feedback.
After students have filled out their blank endocrine diagrams during and after discussion, post U7_L2_EndocrineDiagram_ANSWERS to allow students to check their work and further examine the process.
Student Misconceptions It is very important to mention to students the following points as to not generate any misconceptions: 1) Almost every gland in the body will always be secreting some base line level of hormone. For instance, the pancreas is always secreting insulin. However, only when blood glucose levels rise, does this secretion increase dramatically. 2) Although homeostasis was the center of this lesson it is important that students understand that the endocrine system is not only involved in homeostasis. It is really a system that allows parts of the body to communicate. For instance estrogen and testosterone change the state of the body during puberty.
Before students move on to the next activity, make sure they have a good grasp on what the endocrine system is. Homeostasis and Negative Feedback are important concepts that should be successfully covered before moving on. If needed, develop further lecture and/or discussion on the endocrine system as you see fit.
Activity 3: Insulin/Glucagon Modeling Remind students of the driving question of the lesson: How are glucose levels regulated in the body? Tell students that they will learn how the endocrine system releases hormones to keep glucose levels at homeostasis. Have the students split into groups of 4-5. Before having students work on their models, initiate a short discussion about how insulin and glucose transporters are related. Discuss the “Check-Out Analogy” provided in the document U7_L2_Resource_CheckOutAnalogy and at the end of this lesson plan under Additional Information. Pass out whiteboards/poster sheets, markers, and pre-cut laminated cards from the U7_L2_ Cards_ GlucoseModel _Molecules and the U7_L2_ Cards _GlucoseModel _Organs. Tell students that by reading the information on the back of the cards they can develop a model to explain and communicate the answer to the driving question. Students can use markers to draw blood vessels or anything else they think they may need to add that the cards may not provide. Each group’s model may differ a little but they should all be able to illustrate the system accurately. As the students are constructing their models, remain actively involved; make sure to move about the room looking at the groups’ models, making comments, and asking/answering questions. Students may feel overwhelmed by the new terminology they have received. However, remind students that they already know the fundamental steps of the endocrine system. They are now simply applying a specific example to these fundamental steps.
Student Misconceptions: Many times students have difficulties distinguishing words that are very similar in name. Glycogen and glucagon are two related words that are very easy to confuse. The following strategy can help effectively distinguish the two: The “Y” reflects the branched shape that glycogen assumes. The “U” in glucagon can be seen as the glucagon receptor while the “O” can be seen as the hormone itself that would fit into the “U.”
Activity 4: Scenario Cards The conclusion of the lesson requires students to use their knowledge of their insulin/glucagon model to explain how the body would react in certain circumstances and is an excellent way to formatively assess student attainment of the learning objectives. Pass out one cut-out card from U7_L2_Cards_GlucoseModel_Scenarios to each student group and give them 2-5 minutes to look over their scenario. Gather the entire class around one group’s model. Have the group explain the scenario they were given and then communicate their answers to the entire class using their model. Be certain to ask follow up questions so the group as well as the entire class has a strong grasp for interpreting the models. Repeat this process so that the entire class gets a chance to see how each scenario plays out in the model. Reference U7_L2_Cards_GlucoseModel_Scenarios_ANSWERS for answers. In this lesson students learned how glucose levels are regulated to maintain homeostasis. Tell the students that tomorrow they will learn about how glucose levels are regulated in an emergency.
U7_L2_EndocrineDiagram_Blank o Students should have filled out this document after watching the endocrine video during class discussion. This is a document that students should hold on to as a reference for other lessons and for a summative assessment later on.
All groups should have a completed glucose/insulin model that they can clearly and accurately explain. Students should take a picture of their model with their phones or tablets to use as a study tool.
This document can be completed during class or for homework to help students organize and solidify the main concepts they learned about insulin and glucagon in this lesson. It may be helpful to use this document to quickly review at the beginning of the next lesson.
U7_L2_Assessment_Graphs (Optional) o This is an optional array of assessment items for Lesson 2. You can choose which items you want students to complete. These items can be given for homework, presented to the class the next day to review material, or given as assessment items on a summative assessment.
Additional Information Teacher Content Pedagogical Knowledge: Teaching With Analogies New knowledge attained by working from prior knowledge. Therefore, a helpful teaching strategy is provide examples to students that they are familiar with so that they can make connections between what they already know and what they are learning. Not only does this help in making students grasp content more effectively, the technique asks for students to generate associations themselves making the learning process more ingrained. The following is an example of an analogy to help students understand glucose transporters and why they are needed in the body. THE CHECKOUT LINE ANALOGY: Present the students with the following scenario: You are a manager at a grocery store. Almost always there are customers in the store and therefore there always needs to be at least one or two cashiers at the registers. The lines are usually only 1 or two people long. However, it is now 5 o’clock. People have left work to go shopping. Lines at the registers are now 6-7 people long. What would you do as the manager? To bring more cashiers to the registers. How would this help? Customers will get checked out more quickly. It will be more efficient. Play devil’s advocate and ask? But the people will still pass through lines to buy food at the store? Why does it matter if it’s efficient or not? The customers will not like to shop at the store because of the long lines. It will damage profit and reputation in the long run. After students have responded to the last question, make the connection to glucose. So having people wait in line is damaging to the store. Well glucose homeostasis
works very similar in the body. There is always glucose in the blood and therefore there are always transporters on body cells, just like there were always cashiers to take care of customers. However, when a person eats a meal, glucose levels in the blood rise, very similar to how the amount of customers in the store increased around 5 o’clock. Now the permanent transporters that are always there can take up glucose, but this take times. And just like the grocery store, this is damaging to the body. Therefore, the body signals cells to have more transporters to take up glucose from the blood, just as a manager would tell his/her employees to open up more registers for the customers. By having glucose taken up into the body efficiently, glucose will not damage the body.
Teacher Content Knowledge: Insulin’s Actions on A Cellular Level Upon insulin binding to the insulin receptor a series of changes take place in the cell. Some of insulin signaling causes immediate changes in the body (like decreasing blood glucose) while other insulin signaling induces rapid (glucose uptake and glycogen storage) and long-term (gene expression) changes in the cell. When insulin binds to its receptor the signaling activates the recruitment of glucose transporters to the cell surface. When there is an increase in glucose transporters at the cell surface glucose from the blood enters the cell. Also simultaneously, intracellularly, there are signaling cascades taking place that activate the enzyme glycogen synthase (which is the enzyme responsible for storing free glucose in the cell into glycogen), and simultaneously inactivate the enzyme glycogen phosphorylase (which is the enzyme responsible for breaking down glycogen into free glucose in the cell to be metabolized to make ATP). Also, insulin signaling activates enzymes involved in lipid (fat) synthesis, and inactivates enzymes involved in lipid breakdown. Glucose can be converted into fat when it is in excess in the cell, insulin signaling, relays the message in the cell that glucose is being stored and not used in the cell and so there is excess glucose available to be stored as fat. In addition, insulin signaling activates another gene expression of proteins involved in the insulin signaling pathway, cell growth, and cell survival. Another signaling cascade that is activated by insulin is the initiation of protein synthesis (translation of mRNA into amino acids). Protein synthesis is a very energy consuming process that the cell will only initiate if it has sufficient energy to do so, insulin signaling relays the message in the cell that there is energy available to perform this task. Overall insulin signaling is VERY complex, it induces several changes in the cell but all to meet the same overall goal, to store glucose so that the cell can continue to grow and survive during times of energy deprivation.