Homeostasis and Human Physiology Introduction (Sam Wright)

Title: Homeostasis and Human Physiology Introduction

Principle(s) Investigated: Homeostasis

Standards:

9. As a result of the coordinated structures and functions of organ systems, the internal environment of the human body remains relatively stable (homeostatic) despite changes in the outside environment. As a basis for understanding this concept:

a. Students know how the complementary activity of major body systems provides cells with oxygen and nutrients and removes toxic waste products such as carbon dioxide.

c. Students know how feedback loops in the nervous and endocrine systems regulate conditions in the body.

Materials: Thermometers, Stop Watch, Rubbing Alcohol (to disinfect Thermometers)

Procedure: Give a detailed explanation of the procedure and include diagrams if possible.

1) Students should break up into small groups.

2) One person from each group is chosen to be the athlete to perform a brief amount of cardio exercise.

3) The group should work together to measure the athlete’s resting body temperature, heart rate, and breathing rate.

• Body Temperature: measure with provided thermometer
• Heart Rate: measure pulse at radial or carotid artery for 15 seconds, and multiply by four
• Breathing Rate: measure breaths taken during 15 seconds, and multiply by four

4) The athlete will then perform cardio exercise (running in place, jumping jacks, etc.) for 2 minutes.

5) During this time, group members should record initial data in the quickwrite.

6) When time is called, the group should work swiftly to re-measure the athlete’s stats.

7) The group should record this second batch of data in the quickwrite.

8) Quickwrite data will show vast changes in breathing rate and heart rate, but minimal changes in body temperature.

9) Using a presentation like the one attached, discuss how the body's structures and related functions work to support homeostatis (note: the blank pages on the powerpoint show the quickwrite and related graphs in real-time, but require an external plugin to operate)

Quickwrite:

https://docs.google.com/spreadsheet/ccc?key=0AlC442vateNKdHhlV1haMFpWYjMtV1VqbWdXblYwWlE

Student prior knowledge:

Any amount of prior knowledge is acceptable to perform, complete, and understand this lab. This would be a great middle school lab to introduce the fundamental concept of homeostasis. In a high school setting, it’s good to introduce homeostasis / physiology or to wrap up those units and see how all of the organ systems and life processes relate to one another. For our purposes, I’ve assumed a basic understanding of cellular respiration.

Explanation:

The purpose of this lab is grasp how homeostasis is a consistent theme in life sciences. It is always in the background of how human physiology and general life processes interact. Students learn that although humans have learned to adapt to many environments, there are basic things we need to keep at an equilibrium in order to survive: internal temperature, chemical makeup, glucose levels, water levels, etc. Furthermore, they should recognize that we have many physical and behavioral responses that allow us to maintain these stable internal conditions in the face of an unstable external environment.

With this particular lesson, students learn that body temperature is kept within a narrow range of 97-100 degrees Fahrenheit through involuntary mechanisms: goose bumps, sweating, shivering, vasodilation and vasoconstriction. They also learn that heart rates and breathing rates have a larger allowable range, in order to keep blood oxygen levels and acidity levels within a narrower, healthy range. Exercise is shown to be a stressor that requires bodily reactions to maintain homeostasis. The subject can be expanded to consider other external stressors (glucose-diabetes, water-dehydration), other organisms (ectotherms, plants), and other biological levels (gene regulation).

Questions & Answers: Give three thought-provoking questions and provide detailed answers.

1) Using your knowledge of cellular respiration and the electron transport chain, explain how it helps promote homeostasis and thermoregulation.

The breakdown of a molecule of glucose releases a huge amount of energy. Since energy is often lost as heat, this would be far above the 98.6 degree limit placed on the human body. Instead, the energy is extracted through a multi-step process including the electron transport chain. This way human can harness the energy of glucose while maintaining homeostasis.

2) We’ve discussed what mechanisms kick in when the human body gets too hot. What are some mechanisms for when the human body gets too cold?

Rather than blood vessels dilating, they constrict to keep warmth within the body. We get goosebumps so the little hairs on our body stand up straight and trap warm air. We shiver produce energy. We huddle up to keep body warmth in. We seek sun and warmth.

3) Snakes are ectothermic animals. Explain how this might explain why they only have to eat one meal a week.

Endothermic animals maintain their body temperature by metabolizing glucose, so they need a steady supply of it. Ectothermic animals do not have a stable internal temperature, and instead tend to match its external temperature. For this reason, they rely on behavior rather than food to keep itself warm, and don’t need to eat as often.

Applications to Everyday Life: Explain (don't just list) three instances where this principle can be used to explain other phenomenon.

1) Thermostats. Homeostasis is often designed into automatic mechanisms; the most common example being a thermostat. If you set it to the narrow temperature of 79 degrees on a hot day, the air-conditioning unit will turn on until the internal temperature reaches below 79 degrees, at which point the A/C will turn off. After a while, the internal house temperature will creep up again, and the A/C will come back on.

2) Cancer treatment. Feedback loops and regulatory genes are commonly referenced in terms of cancer. Knowledge of these homeostatic mechanisms may help lead to treatment.

3) Pacemakers. Knowledge of how humans maintain homeostasis can help lead to medical treatment and implants. For example, a goal of artificial pacemakers are now able to respond to different O2/CO2 levels, exercise levels, body temperature, etc. in order to best maintain homeostasis and function seamlessly within the body.

References:

http://bhhs.bhusd.org/ourpages/auto/2010/4/5/45437230/Homeostasis%20and%20Energy%20Lab%20%202009-2010.pdf (inspiration -- there are many labs out there like this)

http://www.biology-online.org/articles/introduction-homeostasis.html

http://www.biologymad.com/resources/A2%20Homeostasis.pdf