2. Endocrine System Hormones & Homeostasis

3. Regulation How we maintain homeostasis  nervous system nerve signals control body functions  endocrine system hormones chemical signals control body functions

4. Nervous vs. Chemical Regulation of Homeostasis Nervous SystemEndocrine System Mode of action Neurons and neurotransmitters Glands and hormones Speed of action QuickSlow Duration of action ShortLong Specificity Targets specific organs Carried to all organs of the body OBJ 47

5. A few glands… Pituitary  many hormones: master gland  Controlled by the hypothalamus Pancreas  insulin, glucagon Stomach  gastrin Ovary  Estrogen, progesterone Testes  testosterone

7. Responding to hormones Lock and key system  hormone fits receptor on “target” cell target cell non- target cells secreting cell can’t read signal

8. 2 Hormone Signaling Pathways Protein hormones  Hydrophilic/water- soluble  Bind to a receptor on cell membrane  Activate secondary messengers Steroid hormones  Hydrophobic/lipid- soluble  Go through cell membrane  Bind to receptors INSIDE the cell OBJ 48

9. Hormone Signaling Pathways Protein hormones Steroid hormones OBJ 48

10. Regulation of Hormone Secretion Antagonistic hormone pairs maintain homeostasis through negative feedback  Analogy: thermostat  Examples: blood sugar level, blood calcium level, acid in stomach. OBJ 49

11. liver pancreas liver Regulation of Blood Glucose blood glucose level (90mg/100ml) insulin liver cells take up glucose from blood liver stores glucose as glycogen (dehydration synthesis) glucagon pancreas liver breaks glycogen into glucose (degradation hydrolysis) and releases into blood high low Negative Feedback Endocrine System Control