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AP Biology

AP Biology. Unit 1 Chapters 1-5. Feedback mechanisms. Regulate biological systems A kind of supply-and-demand economy applies to many biological systems. Many biological processes self-regulate by a mechanism called feedback. Two types: Negative feedback and positive feedback.

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AP Biology

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  1. AP Biology Unit 1 Chapters 1-5

  2. Feedback mechanisms • Regulate biological systems • A kind of supply-and-demand economy applies to many biological systems. • Many biological processes self-regulate by a mechanism called feedback. • Two types: Negative feedback and positive feedback

  3. Negative feedback • In feedback regulation, the output, or product, of a process regulates that very process. • In life, the most common form of regulation is negative feedback. • Results in homeostasis

  4. Example of Negative Feedback • The cell’s breakdown of sugar generates chemical energy in the form of a substance called ATP. When a cell makes more ATP than it can use, the excess ATP “feeds back” and inhibits an enzyme near the beginning of the pathway.

  5. Nonliving example of Negative feedback • Regulating room temperature depends on a control center (thermostat) that detects temperature change and activates mechanisms that reverse that change.

  6. Example of Negative Feedback • When you exercise vigorously, you produce heat, which increases body temperature. Your nervous system detects this increase and triggers sweating. As you sweat, the evaporation of moisture from your skin cools your body, helping return your body temperature to its set point.

  7. Positive feedback • Less common • End product speeds up production. • Does not promote homeostasis • Amplify rather than diminish the stimulus • Helps drive process to completion.

  8. Example of Positive feedback • The clotting of your blood in response to injury is an example. • When a blood vessel is damaged, structures in the blood called platelets begin to aggregate at the site. Positive feedback occurs as chemicals released by the platelets attract more platelets and seal the wound.

  9. Example of positive feedback • During child birth the pressure of the baby’s head against receptors near the opening of the mother’s uterus stimulates the uterus to contract. These contractions result in greater pressure against the opening of the uterus, heightening the contractions and thereby causing even greater pressure, until the baby is born.

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