Unit 3: Homeostasis in Human Body Systems

Phenomena: Marathon Runner Challenge

Performance Task

Challenge: A marathon is a 26.2 mile race. People often train for months leading up to the race in order to successfully complete this type of long distance running challenge. Sometimes, runners aren’t able to finish the race or runners collapse and die shortly after the race. Your challenge is to use your findings from research articles, data sets, and other class activities in order to determine and explain what is causing marathon runners to collapse and sometimes die.

Goal: To determine what is causing a marathon runner to collapse.

Product: Your presentation of your findings will be in the form of a newspaper article, which will explain the physiological issues involved.

PredictingInitial Hypothesis:  Explain why the marathon runners are collapsing and possibly dying.  (I think the marathon runners are collapsing and dying because…)

Digging deeper into the cause of marathon runner dilemma: Concept of Homeostasis!

Learning Target: I can justify the need for homeostasis by all living organisms.

Introduction: The ability of ALL living organisms to maintain a stable internal environment is called homeostasis. Keeping a stable internal environment requires constant adjustments.Homeostasis typically involves negative feedback loops that counteract changes of various properties from their target values, known as set points. In contrast to negative feedback loops, positive feedback loops amplify their initiating stimuli, in other words, they move the system away from its starting state.

Which picture(s) doesn’t fit the description of homeostasis?

Picture(s) Reason: _____________________________________________________

Vocabulary Building:

1) Feedback - information about reactions to a product, a person's performance of a task, etc. which is used as a basis for improvement.

a) If you are getting good grades, you will get a __________ feedback

b) If you are getting low grades, you will get a ___________ feedback

In other words, it is like a reaction to an action.

Class discussion to elaborate the purpose of feedback:

An example would be students receiving progress reports. We will discuss the purpose of progress reports; for students to gauge their performance in there classes.

Students will be asked, “What would you consider normal or acceptable range for your grades? What happens when you fall outside of (below) that range?”

Students should identify that they have to do work and change their behavior in order to get back into that acceptable range.

The teacher will explain that the human body works in the same fashion through the process of homeostasis. The teacher will ask, “What things/processes in the human body need to be kept within a particular range?” Students will generate a list of processes. Further knowledge: Identity the target ranges for those processes.

Hands on Class Activity

Objective: Explain the process of Homeostasis by Negative Feedback Pathways in the human body

This lesson includes a kinesthetic game where students will actively engage in learning about the mechanisms that maintain blood glucose levels in humans.

Unit Topic: Homeostasis

Central Concept: The human body functions through a series of negative feedback pathways. The human organ systems work together to achieve homeostasis. There are a variety of mechanisms and vital functions that are maintained through homeostasis; blood glucose, blood pH, blood pressure, body temperature, O2 and CO2 levels, etc.

Key Terms

Homeostasis, negative feedback, stimulus, receptor, integrating center, effector/target organ, hormone, insulin, glucagon, pancreas, glucose, glycogen

Main Lesson and Activity

Students are given a worksheet with the terms stimulus, receptor, integrating center, effector, and response. They will define these terms based on the analogy of a home heating system. After reading about how a home heating system works, they will identify stimulus, receptor, integrating center, effector, and response in the story. They will then be given three human conditions that are controlled by negative feedback; thermoregulation-hot and cold, blood pressure, and O2/CO2 levels. Students are separated into four groups (4-5 students) and each group is assigned a different process. The teacher gives each group a very brief description of that process.

1. The group members read their description.2. Identify the stimulus, receptor, integrating center, effector, and

response and write these on paper in a list.Ex. Thermoregulation

Stimulus= increase in body temperature

3. The groups now put these components into a flow chart, showing it’s cyclical pattern. They will also indicate where the negative feedback occurs and the system is shut down. Using the basic flow chart below.

4. The groups will report back to the class, sharing their findings and flow chart.

Wrap-up

For homework, students will be given a reading using the ARM PROTOCOL to deepen understanding.

Lesson 2 (Day 2): Blood Sugar Regulation

PreparationPrint out copies of the attached “game pieces”. You should print several (25-40) copies of the “Glucose” and “Insulin” cards. Print 5-10 copies of the “Circulatory System” cards, as you can assign several students to this role. Print one copy of all other cards.

Introduction: Prior Knowledge

Students will use information gained in the prior lesson in order to understand how the human body regulates blood sugar levels. Students will then be asked, “What happens in our bodies after we eat? What type of nutrients/molecules are in those foods?” A list will be generated on the board based on student response. The teacher will turn their attention towards foods containing carbohydrate. Students will be asked, “What do carbohydrates provide for our bodies, our cells?” (This should be review of macromolecules and cellular respiration)

Main Lesson and Activity

The teacher will briefly explain that our cells need a consistent and readily available supply of glucose in order to produce ATP and therefore maintain vital functions. The teacher will show a flow chart of the blood sugar regulation feedback loop, connecting this to the diagrams they generated in the previous lesson. Students will be asked to identify the stimulus, receptor, integrating center, effector, and response to both an increase in blood sugar, and a decrease in blood sugar. The teacher explains how the blood sugar regulation mechanisms work under normal circumstances.

The classroom now becomes the human body and students will kinesthetically demonstrate this process as a class. Students will be placed into teams based on organ systems and each will be assigned a specific structure and task. See the chart below.

System Structure TaskDigestive Mouth

(1 student)Tear the starches in half and pass to stomach

Stomach (1 student)

Break sugars into monomers of glucose andpass to sm intestine

Small Intestine (1 student)

Pass the glucose to the circulatory system

Circulatory Blood(multiple students)

Carry glucose to muscle, liver, brain

Blood(multiple students)

Carry insulin to target organs

Endocrine Pancreas (1 student)

-Command B-cells to release insulin.-Stop insulin production when needed.

Beta cells(could have 2 or more students)

Pass insulin to the circulatory system whentold

Target organs Muscle(1 student)

Takes insulin from blood first, then can then take glucose from bloodLiver

(1 student)Brain(1 student)

Set up this homeostasis game in a circular pattern and instruct the students as follows (see powerpoint for game lay-out):

The (student representing the) mouth is given a polymer of starch, made from the included glucose monomers. He/she is instructed to tear it in half and pass the halves to the stomach.

The stomach separates the remaining pieces into individual monomers and passes them to the small intestine.

The small intestine passes the glucose, individually, to one of the circulatory “runners”

The circulatory runners will walk around the room in a circle.

The pancreas will call out how many runners pass with glucose, calling out “Glucose!”. After he/she has counted out five runners with glucose, he/she will instruct the -cells, “Release the insulin!”

The -cells will pass insulin (from the provided templates) to any circulatory runners who are not carrying glucose.

The insulin runners will pass their insulin on to the target cells (brain, liver, muscle).

Once the target cells have insulin passed to them, they can take glucose from the glucose runners. ***Target cells can only receive a glucose monomer if they are holding an insulin key.

The circulatory runners continue to circle around the room. The pancreas calls out, “Stop insulin production!” once there are no more glucose monomers being passed.

This is the end of the game. The teacher may choose to have students switch jobs and then run the game again (if time permits) to give students more exposure to the function of different organs/structures in this process.The game can also be adapted to include glucagon, -cells, and glycogen. These pieces will need to be designed and printed.

Suggested wrap-up to the activityHave students return to their desks and write a brief description of the activity they just did. Make a list of their classmates, what role they played, and what task they had to perform.

Follow-up exercise

What happens when there is too little glucose in the blood?

The teacher would now explain how glucagon works in opposition to insulin, in order to maintain normal blood sugar levels.

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Name___________________ Date _________________

HW

Learning Target: I can justify the importance of homeostasis for all living things.

What happens if stability is disrupted?

Remove one stone and the whole arch collapses. The same is true for the human body. All the systems work together to maintain stability or homeostasis. Disrupt one system, and the whole body may be affected.

Homeostasis

All of the organs and organ systems of the human body work together like a well-oiled machine. This is because they are closely regulated by the nervous and endocrine systems. The nervous system controls virtually all body activities, and the endocrine system secretes hormones that regulate these activities. Functioning together, the organ systems supply body cells with all the

Focus question: Why do organisms do homeostasis?

Answer: (Mark the portions of the text that helped you answer the focus question).

_______________________________________________________________________________________

Response: Write 1 or 2 real life connections to the phenomena of homeostasis. ________________________________________________________________________________________

Meaning: What does it mean to maintain homeostasis and what is its purpose? ________________________________________________________________________________________

substances they need and eliminate their wastes. They also keep temperature, pH, and other conditions at just the right levels to support life processes.

Why giving the above example might not be a good one to describe homeostasis?

______________________________________________________________________

Maintaining Homeostasis

The process in which organ systems work to maintain a stable internal environment is called homeostasis. Keeping a stable internal environment requires constant adjustments. Here are just three of the many ways that human organ systems help the body maintain homeostasis:

Respiratory system: A high concentration of carbon dioxide in the blood triggers faster breathing. The lungs exhale more frequently, which removes carbon dioxide from the body more quickly.

Excretory system: A low level of water in the blood triggers retention of water by the kidneys. The kidneys produce more concentrated urine, so less water is lost from the body.

Endocrine system: A high concentration of sugar in the blood triggers secretion of insulin by an endocrine gland called the pancreas. Insulin is a hormone that helps cells absorb sugar from the blood.

So how does your body maintain homeostasis? The regulation of your internal environment is done primarily through negative feedback. Negative feedback is a response to a stimulus that keeps a variable close to a set value (Figure below). Essentially, it "shuts off" or "turns on" a system when it varies from a set value.

For example, your body has an internal thermostat. During a winter day, in your house a thermostat senses the temperature in a room and responds by turning on or off the heater. Your body acts in much the same way. When body temperature rises, receptors in the skin and the brain sense the temperature change. The temperature change triggers a command from the brain. This command can cause several responses. If you are too hot, the skin makes sweat and blood vessels near the skin surface dilate. This response helps decrease body temperature.

Another example of negative feedback has to do with blood glucose levels. When glucose (sugar) levels in the blood are too high, the pancreas secretes insulin to stimulate the absorption of glucose and the conversion of glucose into glycogen, which is stored in the liver. As blood glucose levels decrease, less insulin is produced. When glucose levels are too low, another hormone called glucagon is produced, which causes the liver to convert glycogen back to glucose.

What is the mechanism of homeostasis? Explain it your own words. (Hint: read from above and study the following picture before answering).

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Feedback Regulation. If a raise in body temperature (stimulus) is detected (receptor), a signal will cause the brain to maintain homeostasis (response). Once the body temperature returns to normal, negative feedback will cause the

response to end. This sequence of stimulus-receptor-signal-response is used throughout the body to maintain homeostasis.

Failure of Homeostasis

Many homeostatic mechanisms such as these work continuously to maintain stable conditions in the human body. Sometimes, however, the mechanisms fail. When they do, cells may not get everything they need, or toxic wastes may accumulate in the body. If homeostasis is not restored, the imbalance may lead to disease or even death.

Summary

All of the organ systems of the body work together to maintain homeostasis of the organism. If homeostasis fails, death or disease may result.

Review

1. What is homeostasis?

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2. Describe how one of the human organ systems helps maintain homeostasis.

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3. A house has several systems, such as the electrical system, plumbing system, and heating and cooling system. In what ways are the systems of a house similar to human body systems?

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How is Homeostasis maintained in your body? What is the mechanism of Homeostasis?

ThermoregulationWhat did you learn about how the body regulates body temperature?

How will this help you revise your prediction?

Which human body systems are involved in thermoregulation?

Why is maintaining a constant internal temperature necessary?

What happens if the body is too hot? 

o Or too cold?

Are there any environmental conditions during the race that make you think that thermoregulation was a major challenge for runners on the race day?

What symptoms hint that runners were experiencing conditions related to thermoregulation?

Do you believe that thermoregulation was the reason why any of the marathon runners experienced severe medical conditions after the race?

WRITING EXTENSION

A child has had a 104°F fever for several hours.  Why is this considered a medical emergency and contact of a doctor should be immediate?  What could happen to the body if the fever continues?

There are several remarkable stories of people falling into frozen lakes and despite experiencing low body temperatures, they survive!  How is the effect of hypothermia on the body different than hyperthermia?

Glucose RegulationWhat did you learn about how the body

regulates glucose levels?How will this help you revise your prediction?

What substances and body parts Are there any data that suggest glucose

balance was disrupted for any of the

[Grab your reader’s attention with a great quote from the document or use this space to emphasize a key point. To place this text box anywhere on the page, just drag it.]

are involved in the regulation of glucose?

Why is the homeostasis of glucose important to the entire body and its cells?

Do blood glucose levels remain constant throughout the day for diabetics and nondiabetics? 

runners on the race day? What symptoms hint that runners were

experiencing conditions related to glucose regulation?

Do you believe that glucose regulation was the reason why any of the marathon runners experienced severe medical conditions after the race?

WRITING EXTENSION

What types of foods and drinks should marathon runners consider eating/drinking before, during, and after the race?

Circulatory and Respiratory SystemsWhat did you learn about how the

circulatory and respiratory systems work together to maintain homeostasis? 

How will this help you revise your prediction?

How do these 2 systems support the body on the cellular level? 

What body factors change during the race and after exercise?

How do necessary substances, such as oxygen and glucose, move throughout the body and go to where they are needed?

How do the respiratory and circulatory systems work together to maintain homeostasis, particularly during strenuous exercise?

Are there any data that make you think that either of these body systems caused issues for runners on the race day?

What symptoms hint that runners were experiencing conditions related to these body systems?

Do you believe that circulation or respiration was the reason why any of the marathon runners experienced severe medical conditions after the race?

WRITING EXTENSION

Although all human body systems are necessary for survival, how do the circulatory and respiratory systems provide vital substances to every cell in the human body?  Why does a failure of either of these systems quickly lead to possible death?

Regulation of WaterWhat did you learn about how cells maintain proper

water balance?

How will this help you revise your prediction?

What is the importance of water? How does it help maintain life processes?

How do humans regulate fluid / water levels in the body?

How does water move into and out of cells?

Are there any data that make you think that this body system caused issues for runners on the race day?

What symptoms hint that runners were experiencing conditions related to this body system?

Do you believe that the excretory system or hydration was the reason why any of the marathon runners experienced severe medical conditions after the race?

WRITING EXTENSION

Although pure water is often recommended for athletes, how could a specially formulated sports drink potentially support the body’s needs better?

Final TaskWhat happened to runner #XXXX?  

Identify which runner collapsed and explain why. In your answer be sure to discuss the interaction between at least two body systems. You may refer to the organizer above and organize your writing piece in the following manner:

I think....

Because…

[The following are topics that you can draw from to include in your answer] Thermoregulation Respiratory and Circulatory System Interactions Glucose Regulation Water Regulation

Writing Extension

See below for 2 alternative writing tasks at the completion of this unit.

SHORT VERSIONThe Living Environment Examiner

Sports Section“What happened to Runner #XXXX?”

What is a marathon?  How does it affect the human body? What is homeostasis? Which failure of homeostasis affected the runner resulting in death?  Why?

EXTENDED VERSIONThe Living Environment Examiner

Sports Section“What happened to Runner #XXXX?”

Introduction What is a marathon?  How does it affect the human body? What is homeostasis?

Thermoregulation What is it? What is normal? What happens during a marathon? Why is it important to maintain it? What happened to the 6 runners we are tracking?

Respiratory and Circulatory Systems Balance & Interaction What is it? What is normal? What happens during a marathon? Why is it important to maintain it? What happened to the 6 runners we are tracking?

Glucose Regulation What is it? What is normal? What happens during a marathon? Why is it important to maintain it? What happened to the 6 runners we are tracking?

Water Balance What is it? What is normal? What happens during a marathon? Why is it important to maintain it? What happened to the 6 runners we are tracking?

Conclusion What happened to our 6 runners? Which runner had the best time? Which runner experienced a severe condition (or died!)? Why is maintenance of homeostasis vital to everyone, especially marathon runners?

Why Runners Collapse During or After a Race

At this year’s New York City Half Marathon, reigning Olympic 5km and 10km champion Mo Farah of the United Kingdom took on Geoffrey Mutai, one of the best marathoners in the world.Though Mutai bested Farah by a good 17 seconds, that wasn’t the biggest story of the day.Moments after the finish, Mo Farah collapsed to the ground. He was immediately tended to by medical staff at the race and reappeared in good health not too long after at the post-race press conference to allay any fears, but it was still a nerve-racking incident.As any veteran of endurance races knows, runners collapsing either during or after a race is not unheard of.  If you’ve been to enough races, you’ve probably seen this happen first-hand.There are a number of reasons why athletes collapse on race day; some are relatively benign, while others are very serious. In today’s article, we’re going to explore some of those reasons so you can help prevent them and ease any fears a situation like this might have caused.Causes of runners collapsing during and after racesA 2011 scientific paper by Chad Asplund, Francis O’Connor, and Timothy Noakes, three researchers and medical doctors from the United States and

South Africa, investigated the various reasons runners collapse during and after races.Heat strokeHeat stroke is one potential cause—when you run hard, your body generates a large amount of heat, and if you can’t get rid of it effectively, this will result in an abnormally high body temperature. This in turn causes massive, body-wide problems, which manifest as confusion, dizziness, vomiting, and collapse.Dehydration can increase your risk of heat stroke, but it is not the only cause. Outside temperature and a rise it internal body temperature from working hard can also cause heat stroke. And while heatstroke is more common on very hot days, it can happen even on days with moderate weather.Here are 6 helpful strategies for  how to perform well and race safely in the heat.HyponatremiaHyponatremia, a drop in the sodium that circulates in your blood, is another possible cause of collapse.Typically, this occurs in runners who drink far too much water during a race, which dilutes the sodium in their blood so much that it disrupts their body’s normal biochemistry. Hyponatremic runners also commonly vomit, become confused, and collapse.Athletes at greatest risk are novice runners or slower runners who may take 4-5 hours or more to finish a marathon and who are drinking mainly water. These runners often have an easier time drinking while running at a slower pace and also have more time and opportunities to fill up on fluids.As the marathon and other long-distance races become more popular, especially among newer recreational runners, more athletes are likely to be at risk for hyponatremia.For a more in-depth look at hyponutremia and how you can prevent it, here’s a great article   written by our nutritionist Emily Brown and based on the work of Dr. Tim Noakes. You can also check out our podcast with Dr. Noakes himself.

Heart conditionsTraditional heart disease can lead to a heart attack during a race, even in apparently healthy middle-aged runners, and many young runners train and race with undetected congenital heart conditions.One study done in Italy, which requires all young people to undergo cardiac testing before participation in sports, found that 2% of all young athletes had potentially dangerous heart abnormalities. Every year, a handful of high school and college athletes suffer sudden cardiac arrest during athletic events.One well-known case occurred in 2008, when professional runner Ryan Shay collapsed and died only five miles into the Olympic Trials Marathon.It’s always advised to consult your doctor before jumping into a training program, especially if you haven’t been exercising regularly before starting.Postural hypotension (the most likely cause)As worrying as the three conditions above are, there is some good newsAsplund, O’Connor, and Noakes point out that the majority (though not all) of runners who collapse after reaching the finish line of a race are likely suffering from a relatively benign condition called postural hypotension.This happens in part because you’ve stopped running.

During an all-out effort, like a race, your heart rate is sky-high, and as a result, so is your blood pressure. 

Additionally, the rapid, rhythmic contractions of your muscles while you run provide a strong pump-like effect on your blood vessels, encouraging blood to circulate back from your legs.

Once you hit the finish line, both of these mechanisms cease.The result is a sudden drop in blood pressure, which produces dizziness, fainting, and collapse, much like when you stand up too fast after sitting or lying down for a while.Collapse from postural hypotension still needs medical attention, and Asplund, O’Connor, and Noakes provide guidelines for medical personnel treating collapsed runners. But it’s easily treated with leg elevation and oral rehydration, and it’s not a life-threatening condition.

News stories report that this is exactly what happened to Mo Farah after his half marathon.Final messageTo be sure, there are several very serious life-threatening medical problems that can cause a runner to collapse, even after crossing the finish line. But research suggests the runners who are most likely suffering from a serious problem tend to collapse during the race, and most of the runners who make it to the finish line before collapsing are going to be okay.Still, any collapsed runner needs medical attention right away.Knowing the various reasons why a runner might collapse in or after a race could save a life, so it’s worth learning!