1. Feedback Loops
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2. Important Terms
Homeostasis--a property of an organism or system that helps it maintain its parameters (temperature, blood glucose levels, blood calcium levels, heart rate, blood pressure, etc..) within a normal (fairly constant) range of values.
Negative Feedback Loop—A negative feedback loop occurs in biology when the product of a reaction leads to a decrease in that reaction. In this way, a negative feedback loop brings a system closer to a target of stability or homeostasis. Negative feedback loops are responsible for the stabilization of a system, and ensure the maintenance of a steady, stable state. The response of the regulating mechanism is opposite to the output of the event. Examples in the human body include: Thermoregulation; Maintenance of blood glucose levels; Maintenance of blood calcium levels.
Positive Feedback Loop--A positive feedback loop occurs in nature when the product of a reaction leads to an increase in that reaction. If we look at a system in homeostasis, a positive feedback loop moves a system further away from the target of equilibrium. It does this by amplifying the effects of a product or event and occurs when something needs to happen quickly. Examples in the human body include: Breast milk production and release; Childbirth; Blood Clotting.
In plants, fruit ripening is stimulated by a positive feedback loop.

3. Negative Feedback Loop

4. Negative Feedback Loop--Thermoregulation

5. Negative Feedback Loop—Blood Glucose Maintenance
Receptors in the pancreas and control center in the hypothalamus
Effectors
Response
Response
Receptors in the pancreas and control center in the hypothalamus
Effector

6. Negative Feedback Loop—Blood Calcium Ion Maintenance
Effector--Osteoblast
Receptors in the thyroid and control center in the hypothalamus
Response—lower blood calcium levels.
Stimulus
Stimulus
Response—higher blood calcium levels.
Receptors in the parathyroid and control center in the hypothalamus
Effector

7. Positive Feedback Loop—Breast Feeding

8. Positive Feedback Loop—Childbirth

9. Positive Feedback Loop—Fruit Ripening