1. Feedback Mechanisms
Big Idea #2: Biological systems use energy to grow, reproduce, and maintain dynamic homeostasis.

2. Essential Knowledge
2C1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes

3. Dynamic Homeostasis Living things maintain stable internal conditions
Examples in humans:
Temperature pH
Solute concentrations (Ca, Fe, Salt, Glucose etc.)
Heart rate/blood pressure/Breathing rates
Oxygen/CO2 concentrations

4. Responses to environment to maintain homeostasis
Feedback Mechanisms
Responses to environment to maintain homeostasis

5. Negative Feedback
Returns a changing condition back to its target set point.
Ex: Return body to normal conditions

6. Negative Feedback – Hot!!
Beckham sweats b/c he is hot (literally)  Sweat evaporates, removing heat  Becks cools down!

7. Negative Feedback – COLD!!
Cold means Becks is losing heat  shivers/ shakes to generate heat  His body goes through cellular respiration to convert sugar/fat (like he has any)  heat  blood is diverted from skin  Stops losing heat!

8. High blood sugar levels long term cause cell/organ damage
Body Example: Glucose
High blood sugar levels long term cause cell/organ damage
Low blood sugar leads to fatigue, impaired functioning, fainting, brain damage, etc.

9. Pancreatic Regulation
Insulin
Glucagon
Hormone that causes cells to take in glucose
Lowers blood glucose levels
Triggered by high blood glucose levels
Hormone that raises blood sugar levels (breaks down glycogen into glucose)
Triggered by low blood sugar

11. When Feedback Goes Wrong…
Diabetes video clip

12. Body Example: Water When you have too much water  pee it out (ANF)
When you need to save water, anti-diuretic hormone (ADH) is released
Concentrates urine, decreases sweating, inhibits water loss, increases water absorption

13. Response to the stimulus is amplified
Positive Feedback
Response to the stimulus is amplified
i.e. you eat an appetizer, that makes you more hungry so you eat more food

14. Ex: Birth
Contractions start  More contractions leads to more release of oxytocin  Leads to more contractions (frequent and stronger PUSH!