1. HOMEOSTASIS Group 19 Y2012D

2. Everyday your body is affected by many things 3. Is the way your body keep balance 4. Introduction Homeostasis was defined by Claude Bernard and later by Walter Bradford Cannon in 1926,1929 and 1932. Homeostasis is the property of a system that regulates its internal environment and tends to maintain a stable, relatively constant condition of properties. All homeostatic control mechanisms have at least three interdependent components for the variable being regulated: The receptor The control center The effector 5. Claude Bernard and Walter Bradford Cannon 6. Three components of Homeostasis 7. Positive feedback & Negative feedback 8. Definition Positive feedback is a mechanism by which an output is enhanced. Positive feedback mechanisms are designed to accelerate or enhance the output created by a stimulus that has already been activated. Negative feedback mechanisms consist of reducing the output or activity of any organ or system back to its normal range of functioning 9. Example 10. Comparison 11. Thermal Balance 12. Skin diagram 13. Body temperature Normal body internal temperature is 370C Temperatures above this: denature enzymes and block metabolic pathways Temperatures below this: slow down metabolism and affect the brain We need to regulate internal body temperature in order to provide the optimum conditions for enzyme-catalyzed reactions to be carried out. 14. Control of homeostasis When your body gets too hot, your body need cooling down by: sweating, vasodilation, etc When your body gets too cold, your also need warming up by: Shivering, vasoconstriction, etc 15. Water balance 16. How the body control the water level? Maintaining the body fluids at a constant osmolarity therefore involves regulating the volume of water contained within the body. Control of the volume of water excreted by the kidney rests with the hormone anti-diuretic hormone (ADH also known as vasopressin; diuresis means water loss, therefore anti-diuretic hormone can be translated as is anti-water loss hormone). 17. Controlling water level If the level of fluid in the body falls below normal, the subsequent increase in osmolarity is detected by osmoreceptors in the hypothalamus. In response, the hypothalamus releases ADH and also makes you thirsty. In combination, drinking additional fluid and also recovering the maximum fluid volume possible from the urine will restore fluid volume and osmolarity very rapidly, usually within minutes or 10's of minutes. 18. Controlling water level If the level of fluid in the body rises above normal, this will also change the osmolarity of the circulating fluids. The fall in osmolarity is detected by the hypothalamus, which stops producing ADH. In the absence of ADH the kidney allows fluid loss from the body. 19. Salt balance 20. Detection of low Na+ level 21. Compensation and correction 22. Glucose Homeostasis 23. About glucose in the body Glucose is a monosaccharide which represents an essential biological energy source, enabling the generation of ATP following glycolysis Although many tissues can also use fats and protein as an energy source, the brain and red blood cells can only use glucose. Glucose is stored in the body, importantly in the liver, as glycogen. 24. Circulating levels of glucose Circulating levels of glucose are controlled by two enzymes, insulin and glucagon. insulin glucagon 25. High glucose levels In response to high glucose levels, pro-insulin is released from pancreatic beta cells in the islets of Langerhans and is converted to the active form in the blood. Insulin stimulates the uptake of glucose and storage in the tissues as glycogen (glycogenesis). The uptake of glucose into mammalian cells is facilitated by glucose transporters (Glut). T he individual Glut subtypes differ in their tissue distribution, substrate specificity, kinetic properties, and intracellular localization, allowing members of the Glut family to finely regulate whole-body glucose homeostasis 26. Low glucose level In contrast, low glucose levels cause secretion of pancreatic peptide hormone glucagon from alpha cells. Glucagon promotes the conversion of liver glycogen to glucose (glycogenolysis) and release of glucose back into the blood. During starvation and intense exercise, glucose can also be generated from non-carbohydrate precursors (i.e. pyruvate, amino acids and glycerol), in a process called gluconeogenesis. 27. Diabetes mellitus Disruption of glucose homeostasis is most commonly studied in the field of diabetes mellitus, a metabolic syndrome in which patients do not produce suffi cient levels of, or correctly respond to, insulin. 28. Summary Homeostasis and its three basic components Positive feedback and negaive feedback in correcting a false condition The way your body keep its temperature constant How the body balance water level and salt Glucose homeostasis The way your body keep balance 29. Overview 30. Keep yourself healthy 31. Thank you For listening to us