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Homeostasis: Negative and Positive Feedback Loops

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Stacey Cauley

on 16 October 2012

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Transcript of Homeostasis: Negative and Positive Feedback Loops

Negative and Positive Feedback Loops
FOCUS = BLUE text Homeostasis When have you heard the term "feedback" used before? (Ex: "I've heard people say "feedback" when they talk about….)

What are some examples of "feedback"? (think about situations in school, home, jobs, sports, etc)

Write a definition of what you think "feedback" means For example, if you want to keep a pencil in the middle of your desk, you will do what it takes to stop it from rolling off. If the pencil starts to roll to the left, you will push it back to the right. If the pencil rolls to the right, you push it back to the left. Any time the pencil starts rolling from the center, you push in the reverse - opposite or negative - direction! Positive Feedback Loop Humans also have many feedback loops, to maintain homeostasis. There are a variety of mechanisms and vital functions that are maintained through homeostasis, including blood glucose, blood pH, blood pressure, body temperature, O2 and CO2 levels, etc. Homeostasis in Humans: Humans maintain a temperature close to the set point of 37 C (98.6 F)

To keep this constant, the blood vessels can constrict, to retain heat or dilate, causing you to sweat and the muscles can contract causing you to shiver Action = Resistance to changes
Result = Stabilize the changes
Memory Word = Reverse On your sticky note: Negative Feedback Loop 2. Control Center = contains the set point for the variable and
sends signals to the effector Create a Graphic Organizer

Read each human function/process.
1. Identify the sensor, control center, and effector.
3. Make a graphic organizer of the process, showing the cyclical pattern.
4. Be prepared to share with the class. Blood Pressure
When blood pressure increases, the carotid artery receptors again are responsible for detecting the change in blood pressure and send a message to the brain. The brain will cause the heart to beat slower and thus decrease the blood pressure. Decreasing heart rate has a negative effect on blood pressure. Carbon Dioxide
When we exercise our muscles give off carbon dioxide as a waste product. This increase in the level of carbon dioxide in the blood. Carotid artery receptors sense the change in carbon dioxide and send a message to the brain. The brain will then stimulate the lungs to increase respiration. This will lower the amount of carbon dioxide in the blood What would you consider normal or acceptable range for your grades?

What feedback do you get when your grades fall BELOW that range? Who gives you that feedback?

What actions do you need to take when your grades fall BELOW that range?

What actions might you take if your grades ABOVE that range? What's a graphic organizer? Example Flow Chart A flowchart is a type of diagram That represents a process showing the simple steps as shapes Action = Further change caused
Result = Amplify the changes
Memory Word = Intensify Feedback Loops Self-regulating mechanisms used in the body to maintain a "set point" If an individual water buffalo senses a predator, such as a lion, close-by, it will feel emotions of alarm and panic. These emotions quickly spread among the herd of water buffalo, causing a stampede in response. The entire herd tries to escape the danger felt. 3 Features of Feedback Loops:
1. Sensor = detects and measures changes in the variable
being controlled 3. Effector = carries out the corrective action
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