HOMEOSTASISh .pptx

Homeostasis

1. HOMEOSTASIS A.L.MUNDIA

2. Homeostasis It is the ability of the human body to maintain relatively stable internal conditions (temperature, PH, etc) even though the outside world changes continuously . A good homeostasis is indispensable to maintain the organism in good health. Most diseases can be regarded as a result of disturbance of homeostasis.

3. HORMON CONTROL MECHANISM

4. Hormones : Substances secreted by one group of cells that travel through the blood stream and regulate the metabolic functions of other cells. Hormones can affect only cells that have receptors that can bind the hormone Target cells : Those cell types that can be affected by a given hormone

5. Causes the variable to change in a direction opposite to that of the initial change. is self-limiting . And most common ■ A hormone has biologic actions that, directly or indirectly, inhibit further secretion of the hormone. ■ For example, insulin is secreted by the pancreatic beta cells in response to an increase in blood glucose. In turn, insulin causes an increase in glucose uptake into cells that results in decreased blood glucose concentration. The decrease in blood glucose concentration then decreases further secretion of insulin. 1- Negative feedback mechanisms : or

6. Causes the variable to accelerate the change in the same direction that the initial disturbance. is rare. ■ is explosive and self-reinforcing. ■ A hormone has biologic actions that, directly or indirectly, cause more secretion of the hormone . ■ For example, the surge of luteinizing hormone (LH) that occurs just before ovulation is a result of positive feedback of estrogen on the anterior pituitary. LH then acts on the ovaries and causes more secretion of estrogen. 2- Positive feedback mechanisms : or

7. Blood Glucose Homeostasis

8. Blood glucose homeostasis Top threshold: 110 mg/dl Bottom threshold: 70mg/dl Hyper glycemia: concentrations above 110 mg/dl Hypo glycemia: concentrations below 70 mg/dl

9. Importance of blood glucose homeostasis Brain uses 25% of blood glucose. It is dependent on stable glucose levels! Hypo glycemia: leads to coma/death Hyper glycemia leads to long term damage of eyes, blood vessel, organs (kidney)

10. Pancreas carries out Blood Glucose Homeostasis two hormones used for regulation 1.Insulin 2.Glucagon

11. Pancreas regulates blood sugar β -cells produce Insulin α -cells produce Glucagon

12. Insulin Lowers blood glucose levels!!! Is released when blood glucose rises above 110 mg/dl Forces liver and muscles to take up glucose from blood stream Forces liver to make glycogen (animal starch) by linking glucose molecule together

13. Glucagon Raises blood glucose Is released when blood glucose falls below 70 mg/dl forces liver break down glycogen into glucose and release it into the blood stream

14. TEMPERATURE HOMEOSTASIS

15. All mammals maintain a constant body temperature. Human beings have a body temperature of about 37 º C. E.g. If your body is in a hot environment your body temperature is around 37 º C If your body is in a cold environment your body temperature is still around 37 º C

16. What mechanisms are there to cool the body down? Sweating When your body is hot, sweat glands are stimulated to release sweat. The liquid sweat turns into a gas (it evaporates) To do this, it needs heat. It gets that heat from your skin. As your skin loses heat, it cools down.

17. Sweating The skin

18. What mechanisms are there to cool the body down? Vasodilation Your blood carries most of the heat energy around your body. There are capillaries underneath your skin that can be filled with blood if you get too hot. This brings the blood closer to the surface of the skin so more heat can be lost. This is why you look red when you are hot!

19. If the temperature rises, the blood vessel dilates (gets bigger). This means more heat is lost from the surface of the skin

20. What mechanisms are there to warm the body up? Vasoconstriction This is the opposite of vasodilation The capillaries underneath your skin get constricted (shut off). This takes the blood away from the surface of the skin so less heat can be lost.

21. If the temperature falls, the blood vessel constricts (gets shut off). This means less heat is lost from the surface of the skin

22. What mechanisms are there to warm the body up? Piloerection This is when the hairs on your skin “stand up” . It is sometimes called “goose bumps” or “chicken skin”! The hairs trap a layer of air next to the skin which is then warmed by the body heat The air becomes an insulating layer.

23. WONDERFUL