Physiology 206 1STedition Lecture 34 Outline of Last Lecture I Glucocorticoid II Aldosterone III Adrenal Medulla IV Insulin Diabetes Outline of Current Lecture V Glucagan VI Calcium VII Bone VIII Vitamin D Current Lecture Glucagan Everything that is true for insulin is opposite for glucagan It is the balance between glucagan and insulin that determines whether we are in fed or starving state Insulin and Glucogan are both peptides Regulation of Blood Calcium Levels closely regulated Three Hormones Involved 1 Parathyroid Hormone These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 2 Calcitonin 3 Vitamin D Regulation of Ca automatically regulates PO4 Distribution of Calcium in Body 99 in teeth and bones 0 9 Soft Tissues 0 1 ECF half free half bound Free is what we can regulate 0 05 Level of calcium in plasma reflects the amount of calcium intaken into plasma and the amount being taken out Renal exceretion removes calcium Calcium absorbed through gut goes to body Amount absorbed is not necessarily the amount eaten When loss of calcium exceeds the rate of intake body immoblizes it from bone In additino to endocrine regulation of calcium release from teeth and bone there is endocrine regulation of intake and output When changes in plasma levels of calcium rapid but not precise adjustments involve adjustments of moving calcium back and forth from bones The long term precise adjustments occur in kidneys Primary regulator is Parathyroid Hormone Effects 1 Bone 2 Kidney 3 Amount of absorption from gut overall effect is that it increases plasma calcium levels Bone Bone is metabollically active Matrix made up of collagen and CaPO4 what makes it hard Is constantly reabsorbed and reformed way that happens is the reabsorption and reformed the laying down new stuff is most rapid in areas of stress While this is happening CalciumPhosphate is being released by bones the collagen is being removed and laid back down again Collagen goes where stress is and calciumphosphate forms on collagen Parathyroid Hormone 1 induces loss of calcium from fluid within bones into plasma 2 Accelerates the disolution of bone all extra calcium ends up in plasma major effect is it raises calcium levels in plasma give you less dense bones Control of Parathyroid Hormone Direct Response to plasma calcium levels level goes down hormone released Kidneys when remove calcium from bones brings Phosphate with it if nothing happened would form crystals in plasma Parathyroid hormone causes kidneys to release more phosphate into renal excretion Absorption from Gut Parathyroid hormone doesn t do anything directly Effects Vitamin D Calcitonin thyroid gland also produces decreases rate of reabsorption of bone not very physiologically important Vitamin D derivitive of cholesterol cannot absorb calcium in intestine without Vitamin D Two Sources 1 can synthesize it in skin when exposed to sunlight hardly ever adequate source clothes hair block sun 2 Diet gets added to milk Doesn t do anything until it goes through 2 steps 1 Liver transformed then goes to 2 Kidneys converted to Activated Vitamin D what promotes calcium absorption in gut In absence of Activated Vitamin D no calcium absorbed Parathyroid Hormone accelerates the conversion of Vitamin D into Activated Vitamin D When plasma levels of calcium falls parathyroid increase bone and kidney and increases conversion of Vitamin D into Activated Vitamin D Will lose bone deficiency by calcium or Vitamin D defciency
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