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Animal Form & Function Homeostasis. AP Biology Bloomington High School. Definition. Controlling the internal environment Maintenance of stable internal environment. Negative Feedback. Response produced opposes stimulus Homeostasis restored. Positive Feedback.
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Animal Form & FunctionHomeostasis AP Biology Bloomington High School
Definition • Controlling the internal environment • Maintenance of stable internal environment
Negative Feedback • Response produced opposes stimulus • Homeostasis restored
Positive Feedback • Response produced reinforces stimulus • Homeostasis not restored - disruption continues • Rare • Example – Childbirth
Mechanism Disruption detected by receptors Homeostasis Disruption Control Center evaluates information & directs response Effector produces response that restores homeostasis
Controlling Body Temperature Temperature receptors in skin & hypothalamus detect increase temperature Hot Day in the sun Homeostasis Control Center Hypothalamus Evaporative cooling Heat lost from skin Sweat glands increase secretion Blood vessels in skin dilate
Controlling Body Temperature Temperature receptors in skin & hypothalamus detect decrease temperature Cold day in January Homeostasis Control Center Hypothalamus Heat generatedHeat conserved Muscles contract - Shiver Blood vessels in skin constrict
Controlling Blood Glucose Levels Blood glucose levels rise Eating an ice cream sundae Homeostasis Normal Glucose Levels Beta cells in pancreas release insulin Cells take in glucoseBlood glucose levels drop
Controlling Blood Glucose Levels Blood glucose levels fall No breakfast today Homeostasis Normal Glucose Levels Alpha cells in pancreas release glucagon Breakdown of glycogen in liver & skeletal musclesBlood glucose levels increase
Controlling Blood Calcium Levels Blood calcium levels rise Got Milk & a whole mess of Ca2+ Homeostasis Normal Calcium Levels Thyroid releases calcitonin Ca2+ deposited in boneKidneys reduce uptake of Ca2+Blood Ca2+ levels drop
Controlling Blood Calcium Levels Blood calcium levels fall Milk – I’m supposed to drink milk? Homeostasis Normal Calcium Levels Parathyroid releases parathyroid hormone (PTH) Ca2+ released from boneKidneys increase uptake of Ca2+Blood Ca2+ levels rise