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

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

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

Responses to environment to maintain homeostasis Feedback Mechanisms Responses to environment to maintain homeostasis

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

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

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!

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.

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

When Feedback Goes Wrong… Diabetes video clip

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

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

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