Endocrine Physiology ca homeostasis.pptx

Endocrine Physiology ca homeostasis

1. Endocrine system Physiology

2. Presented by/  Dr/ dina hamdy merzeban

3. Endocrine control of calcium metabolism

4. Calcium distribution in the body Plasma Ca++ concentration is one of the most tightly controlled variables in the body

5. Calcium distribution in the body About 99% of the Ca 2+ in the body is in crystalline form within the skeleton and teeth About 0.9% is found intra-cellular within the soft tissues Less than 0.1 % is present in the ECF Half of the ECF Ca2+ either is bound to plasma proteins and therefore restricted to the plasma or is complexed with PO4 3 The other half of the ECF Ca2+ is freely diffusible and can readily pass from the plasma into the interstitial fluid and interact with the cells The free Ca 2+ in the plasma and interstitial fluid is biologically active and subject to regulation.

6. The function of ECF Ca 2+ :

7. The function of ECF Ca 2+:

8. The function of ECF Ca 2+: Neuromuscular excitability: A fall in free Ca 2+ results in over-excitability of nerves and muscles, conversely, a rise in free Ca 2+ depresses neuromuscular excitability and causes cardiac arrhythmias, {A ↓ in free Ca 2+ increases Na + permeability, with the resultant influx of Na + moving resting potential closer to threshold (depolarization)}.

9. The function of ECF Ca 2+: Excitation- contraction coupling in cardiac and smooth muscle. Stimulus-secretion coupling: The entry of Ca 2+ into secretory cells, triggers the release of the secretory product by exocytosis.

10. The function of ECF Ca 2+:

11. The function of ECF Ca 2+:

12. Control of Ca 2+ metabolism

13. Control of Ca2+ metabolism includes regulation of both:

14. Regulators  of Ca2+ metabolism three hormones

15. Regulators  of Ca2+ metabolism three tissues

16. Parathyroid gland

17. Parathyroid gland

18. Parathyroid gland contain two types of endocrine cells

19. Parathyroid hormone

20. Mechanism of action of PTH

21. The actions of PTH

22. Action  of PTH on bone BONE PTH uses bone as a bank from which it withdraws Ca2+ as needed to maintain plasma Ca2+ level PTH has two major effects on the bone that raise plasma Ca2+ concentration

23. First NB: Labile pool is small Ca pool less than 1%. It is in the form of calcium phosphate, which is present in physico -chemical equilibrium with the plasma calcium.

24. First

25. Second NB: Stable pool is large Ca pool more than 99%. It is in the form of calcium hydroxyapatite in the mature bone. It is not ready exchangeable with plasma calcium.

26. PTH's chronic effect

27. Action  of PTH on kidney

28. Action  of PTH on intestine

29. The PTH induced removal of extra PO43- from the body fluids is essential for  preventingreprecipitation  of Ca2+ freed from bone. Because of the solubility characteristic of Ca3 (PO4)2 salt.

30. The solubility product = plasma concentration of Ca2+ X plasma concentration of PO 3- = constant.

31. A rise of their concentrations will raise this value above the solubility product and results in the precipitation of the salt When plasma PO43- level rises, some plasma Ca2+ is forced back into bone through hydroxyapatite crystal formation, reducing plasma Ca level and keeping constant the calcium phosphate product

32. Regulation of PTH levels

33. calcitonin

34. Calcitonin

35. calcitonin

36. Calcitonin ON BONE

37. Calcitonin on kidney

38. Regulation of calcitonin secretion

39. Vitamin D It is a steroid like hormone essential for Ca2+ absorption in the intestine

40. Sources

41. Synthesis

42. Vitamin D3

43. Function of vitamin D Increase Ca2+ and PO43- absorption in the intestine

44. Function of vitamin D

45. Regulation of plasma ca

46. Regulation of plasma ca

47. Regulation of plasma ca

48. Regulation of plasma ca

49. Calcium Disorders

50. Calcium Disorders

51. PTH hyposecretio n 

52. Vitamin D deficiency