1.1.2. Homeostasis Overview

Prior Knowledge Quick Write: How does your body work to maintain homeostasis? (Think about how your body respond to changes in temperature. What does your body do when you are hot? What does your body do when you are cold?)

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Please read and mark the text below. If you are unfamiliar with how to mark the text, please read the following instructions:

1. Before reading, please number the paragraphs. (Start with the number one and continue numbering sequentially throughout, placing the number near the start of the paragraph.)
2. Circle key terms and other essential words or numbers.
3. Put a box around any terms you do not know the meaning of or are unfamiliar with.
4. Underline information relevant to the reading purpose (concerns, claims, data, definitions, descriptions, evidence, examples, explanations, guiding language, hypotheses, “if then” statements, main ideas, methods, processes, etc.)

Homeostasis is a process that living organisms use to stay alive! Living things are able to maintain homeostasis through negative feedback mechanisms. Negative feedback mechanisms help living things keep their internal conditions (temperature, pH, etc.) balanced by reducing changes in a system. For example, if your body temperature is too high, your body will produce sweat to reduce your body temperature. If your body temperature is too low, your body will shiver to increase your body temperature. Most homeostatic responses in your body are controlled by negative feedback mechanisms (other examples of negative feedback in the body include: blood pressure, breathing and pulse rates).                

Please look at Figure 1.1.2 below. Please write a brief description regarding why you think this image was chosen for this lesson.

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Figure 1.1.2 Brass Scales by Toby Hudson / Creative Commons Attribution-Share Alike 3.0 Unported

Negative feedback works like a home heating/cooling system. Imagine the thermostat in your house or apartment is set at 70 degrees. The furnace works to reduce any changes in temperature. If the temperature falls below 70 degrees, the furnace turns on to increase the temperature. If the temperature rises above 70 degrees, the furnace turns off to decrease the temperature. Remember, negative feedback systems reduce changes in a system and tend to keep a system in balance or equilibrium.

Positive feedback systems are rare in the body and result in an amplified (increased) change in the system (like blood clotting and labor contractions). Negative and positive feedback have opposite effects (positive feedback increases a change; negative feedback reduces a change).

Comprehension Quick Write: Blood glucose (sugar) levels increase after you eat and then decrease once digestion is over. Hormones are secreted in your body to help maintain homeostasis by regulating blood glucose (sugar) levels in the body. Do you think blood glucose (sugar) regulation is an example of negative or positive feedback in the body? Why?

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Video Clip:

Please watch Paul Anderson's video clip from Bozeman Science titled: Unit 4 Review - Homeostasis for an overview of negative and positive feedback. .

Imagine your friend is absent from school today and missed the video clip. You decide to send your friend a “text” to provide a brief summary of the main ideas from the video clip. Please write your “text” in the space below.

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Vocabulary Check: Please fill in the vocabulary table found at the beginning of this lesson for term #1 (definition of homeostasis and extra practice: use the term homeostasis in a sentence).