Thermal Station 3.1 Lab
Thermal Systems in Health Fields
How the Body Regulates its Temperature
- Goal: The goal of this station is to correctly identify how the blood vessels respond to changes in temperature in order to regulate heat loss, and to analyze how sweating helps to accelerate heat loss.
- Materials Required:
- Carolina “Thermoregulation Kit”
- Hot plate
- Ice bucket filled with ice
- Stop watch
- Beaker containing water kept warm with the hot plate
- Beaker containing water kept cool in the ice bucket
- Paper towels
- Pencil and colored pencils
- Answer sheet
- Objectives for Experiment:
- Define thermoregulation and state the temperature range that the body must maintain to be in homeostasis.
- Describe the mechanisms the body uses to speed up heat loss.
- Describe the mechanisms the body uses to conserve heat.
- Correctly define the terms in bold from the introduction.
- Correctly answer application questions relating to the lab experiment.
- Prerequisite Knowledge: Minimum 6th grade reading level. All instructions are provided.
- Applied HealthTerminology: Like many professions, the medical field has its own vocabulary. We have created flashcards to help you learn some of the vocabulary related to temperature regulation in the human body. You can find these flashcards on the computer at the site below.
Instructions to site:
Click on the link below.
https://quizlet.com/84384183/flashcards
Then click on the “Flashcards” button in the upper left corner of the screen.
For each card, say the word out loud or in your mind and try to say what you think the definition is.
Flip the card by clicking on it and say the definition listed out loud or in your mind.
- Evaluation: Your lab performance will be evaluated by the criteria (standards) you will find in this project’s rubric. A rubric is simply a table that states how you will be evaluated. Your coach will use this table to report your performance.
CLICK HERE TO GO TO THE RUBRIC
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INTRODUCTION
Have you ever wondered why you get ‘goosebumps’ and start shivering when you are cold?
https://commons.wikimedia.org/wiki/File:Goose_bumps.jpg
Or have you wondered why you sweat when you are hot?
https://www.flickr.com/photos/mitopencourseware/3971218827
Thermoregulation
We all know that there is a certain range of temperatures that our bodies need to maintain in order to keep everything working normally. The majority of our body heat is produced by normal metabolism (meh-TAB-ole-ism), which involves all of the biochemical processes going on in the body. The activities we perform and the environment also contribute to overall temperature. When you exercise, your body heats up greatly because you are burning through nutrients to gain energy; when you are walking through the park in the middle of the day, your body is absorbing heat from the sun; and when you are standing outside on a winter day, your body is losing heat to the cold air around you.
 https://commons.wikimedia.org/wiki/File:Caribbean_flamingo.jpg |
Despite all of these factors, humans have the ability to maintain a healthy core temperature (the temperature of the deep tissues like the heart, lungs and vital organs), using several different mechanisms. This ability is called thermoregulation (THERM-oh-reg-you-LAY-shun). Any animal that is able to self-regulate their body temperature is called an endotherm (en-do-THERM) commonly referred to as “warm-blooded.” |
Humans and other endotherms are able to be in hot or cold environments and still maintain the same healthy core temperature.
| Other animals called ectotherms, which we often call “cold-blooded,” depend completely on the environment to regulate body temperature. These animals therefore must look for shade or cooler areas when they are hot, and must seek warm, insulated areas when they are cold. Have you ever seen a lizard basking in the sun? He has to do that in order to warm up! |  |
Temperature regulation is an important part of homeostasis (HOME-ee-oh-STAY-sis),which is when all of the systems in the body are in a balanced state to maintain overall health. There are different beliefs as to what the “normal” body temperature should be, but the accepted range is between 97.5° and 100° Fahrenheit (degrees Fahrenheit is usually abbreviated as simply °F). You’ve probably heard that the ideal temperature is about 98.6°F. This may also be written as 37° Celsius, which is another scale for measuring temperature that is used by scientists and most other countries of the world (abbreviated as °C). This range is for an adult person at rest with an ambient temperature (the temperature of the environment around you) of dry air between 68 and 130°F (between 20 and 54.5°C).
Temperature Control Center
The control center for thermoregulation is in a part of the brain called the hypothalamus (HI-poe-THAL-uh-mus). This very small part of the brain at the bottom of the cortex can be thought of as the body’s thermostat.
https://commons.wikimedia.org/wiki/File:Hypothalamus_image.png
The hypothalamus is part of the autonomic (aw-toe-NOM-ic) nervous system, which controls processes that are involuntary. We do not consciously tell our hypothalamus to jump start the body’s automatic thermoregulatory (therm-oh-REG-you-luh-tor-ee) mechanisms. (Other behaviors that we do voluntarily, such as putting on more clothes when we’re cold or looking for shade when we’re hot, are controlled by different parts of the brain.)
The body has ways to either prevent or accelerate heat loss. The hypothalamus has a specific temperature that it tries to maintain at all times, called the set point. When something causes the core temperature to go up or down, the hypothalamus will trigger regulatory mechanisms to bring the body back to the set point.
Temperature and Heat
What are the actual definitions of temperature and heat? Temperature is actually the average energy associated with how fast atoms or molecules are moving. As you sit here reading this, all of the molecules in your body are actually moving and vibrating. When your temperature increases, this means that those same molecules have more energy and are moving faster or vibrating more.
The universe is always trying to get into perfect balance, so energy has a tendency to spread out so that it is evenly distributed. This means that quickly moving molecules want to give away some of their energy to other molecules that are moving slowly so everything is equal. Heat is the transfer of energy from something with a high temperature to something with a low temperature. So something is hot because its molecules have a lot of energy, and something that is cold just has less energy.
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This is why when you pick up a cup of coffee it feels really hot! The heat you are feeling is the energy being transferred to your hand. Over time though, the coffee will eventually cool off. The molecules in the coffee are losing energy to the molecules in the air. The same is true for a cup of soda on ice; the molecules in the soda get cooler because they are losing energy to the extremely cold ice. |
Heat Loss
So now that we know what temperature and heat are, how is heat transferred? There are actually three ways:
- Conduction (con-DUCK-shun) is heat transfer between two objects or substances that are actually touching. For example when you pick up that cup of hot coffee, you are feeling heat from the cup by conduction.
- Convection (con-VEK-shun) is heat transfer through fluids, meaning either through air or water. For example, boiling water is a good example of convection. The heat passes from the burner into the pot, heating the water at the bottom. Then, this hot water rises and cooler water moves down to replace it, causing a circular motion.
- Radiation (ray-dee-AY-shun) is when heat is given off directly from an object or substance, without needing a fluid to pass it on. A good example would be heating a tin can of water using a Bunsen burner. Initially the flame produces radiation which heats the tin can. The tin can then transfers heat to the water through conduction. The hot water then rises to the top, in the convection process.
Click on the link below to see some animations of the three forms of heat transfer using a home as an example, and then test your understanding with the activity at the end.
https://www.e-education.psu.edu/egee102/node/2053
Heat is lost from the body in all three of these ways. The body may take advantage of these in order to get rid of excess heat, or may try to prevent these processes in order to save heat.
Check out this video for a summary of all of the stuff we’ve learned so far:
https://www.youtube.com/watch?v=TSUCdLkI47
How the Body Cools Itself Down
 Modified from https://en.wikipedia.org/wiki/Thermography |
All endotherms are constantly producing heat from metabolism, which we commonly call our body heat. Body heat is always being lost to the environment through radiation (we are giving heat off directly, without needing a fluid to transfer it to something else). |
| We also lose a small amount of heat through respiration (each time we breathe). This is because when we take in a breath, the body heat we have inside is partially transferred to the air in our lungs. That’s why when air is exhaled, it is slightly warmer (and we often use this by blowing into our hands to warm them up!) This is a form of heat transfer through convection because the air is carrying heat away from our bodies. |  |
But many times the heat we lose naturally through radiation of body heat and respiration is not nearly enough to keep the body cool during heavy exercise or a hot day. That’s when the hypothalamus steps in.
If the body heats up too much, the hypothalamus sends messages to the body to trigger several processes that help to accelerate heat loss:
| Vasodilation (VAY-zo-die-LAY-shun) is when the blood vessels of the body open up or expand. This means that the tiny vessels that lie just under the skin get wider and allow more blood to flow close to the surface. |  |
Blood is generally very warm and carries a great deal of our inner body heat, so allowing it to flow so close to the skin surface allows more heat to be released to the environment through radiation. It is because of vasodilation that someone who has been exercising or sitting in a sauna appears red, also called flushed.
The increased blood flow to the skin also helps to activate the sweat glands; the body’s other major way to increase heat loss.
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Perspiration (per-sper-AY-shun), or sweating, begins around 98.6°F. Even though most of us find this mechanism fairly gross, it is very important to our survival. Humans actually have about 2.6 million sweat glands in the skin! |
Sweating makes use of the fact that water, the main ingredient in sweat, is able to absorb MUCH more heat than air. As a drop of sweat forms on your skin, it immediately begins taking in heat from your body. Eventually, once the droplet has absorbed all the heat it can, the sweat begins to evaporate, or turn into gas. Then all of the heat that was stored in that droplet is pulled off of the body. The more our core temperature increases, the faster and more we tend to sweat.
Here is a summary of the cycle the body goes through when core temperature begins to rise:
When the Core Temperature is Too High
This cycle is vital to survival. Hyperthermia (hi-per-THERM-ee-uh)is an abnormally high body temperature that can have many causes. If the body is unable to cool itself and reaches a core temperature of 99.5–100.9°F, it is called mild hyperthermia. Over time this can result in heat exhaustion which is basically extreme weakness due to loss of water and salts through sweating.
Eventually the body will enter full hyperthermia and heat stroke, in which the body is not able to get rid of heat effectively and thermoregulatory mechanisms shut down. Someone having a heat stroke will have a temperature above 105°F, and will often completely stop sweating. They may even pass out, have seizures or heart failure, and eventually die.
Note: A fever is a form of hyperthermia (usually above 100.4°F) that the body uses to kill invading bacteria or viruses. This is actually very effective, because most things that get us sick do the best at our natural body temperature.
How the Body Conserves Heat
As we said earlier, our bodies are constantly losing heat to the environment through radiation of body heat and respiration. So what does the body do to prevent heat loss when we get cold?
If the core body temperature drops too far below 98.6°F, the hypothalamus sends messages to the body to trigger several processes that help to prevent heat loss:
Modified from https://commons.wikimedia.org/ wiki/File:Vasoconstriction_and_Vasodilation.png |
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This makes it harder for heat to escape the body through radiation. It is because of vasoconstriction that someone who has been out swimming in a cold lake or walking out in a snowstorm appears pale.
- Shivering Thermogenesis (THERM-oh-JEN-i-sis) is when the body’s skeletal muscles quickly burn through energy in order to make short and fast muscle contractions, which we know as shivering. Over time this can increase natural body heat, because even though a great deal of the energy being burned is going toward making the muscles contract, some of that energy is lost as heat.
- Hormonal Thermogenesis is when the thyroid and adrenal (uh-DREEN-uhl) glands release hormones that can increase overall metabolism. A special mechanism is also triggered in parts of the body containing a tissue called brown fat. Inside the brown fat cells, nutrients are broken down and used to generate heat rather than burn energy-storing molecules. Brown fat is much more common in infants because they have a harder time staying warm, and humans will lose most of this special tissue as they get older.
You may now be wondering, what about goosebumps? What do they do?
Goosebumps are actually caused by something called piloerection (PIE-low-ee-RECK-shun), or your hair standing up. Each hair on your body has a tiny muscle connected to its follicle that causes this to happen.
This is actually a leftover mechanism from our caveman days, when we had A LOT more hair. When there is a lot of body hair, piloerection forms an insulating layer that traps in air, which is then warmed by body heat. Similarly, furry animals are kept warm by air trapped in their fur. Since we have so little body hair now, it doesn’t effectively prevent heat loss in humans anymore.
Here is a summary of the cycle the body goes through when core temperature begins to fall:
When the Core Temperature is too Low
If the body is unable to warm up, the core temperature may continue to drop and this can cause severe problems with the body’s internal organs, until they eventually just shut down.
Any core temperature below 95°F (35°C) is called hypothermia (HI-poe-THERM-ee-uh). There are stages of hypothermia based on how low the core temperature gets, and each has its own symptoms:
- Mild hypothermia is present between 90-95°F (32-35°C). The person will usually be awake and shivering.
- Moderate hypothermia is present between 82-90°F (28-32°C). The person may be drowsy and has stopped shivering.
- Severe hypothermia is when the temperature is between 68-82°F (20-28°C). By this point the person is probably unconscious and is not shivering.
- Profound hypothermia is a core temperature less than 68°F (less than 20°C). The person essentially appears dead, with no pulse or breathing. (BUT -The person may not actually be dead! Some people at this stage have been found to have their pulse and breathing return when rewarmed!)
Cold exposure may also cause other conditions on parts of the body.
 https://commons.wikimedia.org/wiki/ File:Frostbitten_hands.jpg |
Chilblains are painful areas of redness, swelling, and sometimes blisters that appear on the skin after repeated exposure to cold. Eventually these areas will heal. |
| Frostbite on the other hand is when the tissue actually freezes and cells die. There are different degrees of frostbite, but severely frostbitten tissue is often permanently damaged and must be removed. |  https://commons.wikimedia.org/wiki/File: Human_toes,_12_days_post-frostbite.jpg |
Process Summary: At this station you will…
- Review the medical vocabulary and read instructions on how to perform an experiment related to temperature regulation.
- Observe and record how different temperatures are distributed on the surface of the hand.
- Compare temperature distribution on the hand to different parts of the forearm.
- Observe and record how immersion in warm water changes the distribution of temperatures on the surface of the hand.
- Observe and record how immersion in cold water changes the distribution of temperatures on the surface of the hand.
- Explain what is occurring to cause the changes that you observed in each test.
- Observe and record how evaporation of water from the skin changes the distribution of temperatures on the surface of the hand.
- Explain why evaporation of water from the skin causes the changes that you observed.
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Links to Station 3.1 Modules
Lab Intro | Lab Presentation and Practice | Communications Intro| Communications Presentation and Practice| Math