2. Homeostasis Brain CT-scan

3. Importance of Homeostasis in Mammals  metabolic reactions are controlled by enzymes  enzymes work best in a narrow range of temperature & pH only  ∴ important to keep internal environment as steady as possible

4. Definition: Keeping the internal environment in a Steady state It is controlled by Negative Feedback Mechanism

5. Rise above normal value Fall below normal value Corrective Mechanism NEGATIVE FEEDBACK MECHANISM normal value negative feedback

6. Parts of Body involved kidneys : regulate water & mineral salts concentration skin : regulate body temperature liver & pancreas : regulate blood glucose level

7. 1. Osmoregulation (Water & Mineral salts) Regulate water potential in Tissue Fluid Organ involved: KIDNEYS

8. Normal Water Content in Blood After Sweating Concentrated Blood Larger proportion of water is reabsorbed Concentrated Urine is produced

9. Normal Water Content in Blood After Drinking Diluted Blood Smaller proportion of water is reabsorbed Diluted Urine is produced

10. After having a very salty meal  produce concentrated urine to remove excess salts in solution form  extra water is needed to be excreted along with the excess salts  sensation of thirst (drink more water to compensate for the water loss)

11. 2. Thermoregulation (Regulation of Body Temperature) Homoiotherms (warm-blooded animals) keep body temperature constant even in winter by increasing metabolic rate e.g. birds, mammals

12. 3. Regulation of Blood Glucose Level  controlled by Negative feedback mechanism  controlled by insulin secreted from the islets of Langerhans in pancreas  Diabetes - malfunction of pancreas (does not secrete enough insulin)

13. Liver converts glycogen to glucose normal blood glucose level Blood glucose level falls Soon after a meal Long after a meal Blood glucose level rises normal blood glucose level Too High Too Low Pancreas secretes insulin Pancreas secretes less insulin Liver coverts glucose to glycogen

14. Endocrine Overview Hormones- chemical messengers travel through body Target cell or organ- organ or cells that a hormone affects

15. Control of Hormone Release Negative feedback mechanism- hormone release is triggered by stimulus, rising levels of hormone inhibit further release Endocrine stimuli- Hormonal- hormones stimulate the release of others Humoral- blood stimulates release of hormones Neural- nerves stimulate hormone release