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35 Cards in this Set
- Front
- Back
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Majority of calcium is found where?
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Bone- 99%
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What is the biologically active form of calcium?
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Ionized
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ECF Calcium is found?
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1. Ionized- 50%
2. Bound to plasma proteins- 40% 3. Complex w/ plasma ions (phosphate, citrate)- 10% |
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ECF Ca concentration is controlled by which 3 hormones?
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1. PTH
2. Calcitonin 3. Vitamin D3 |
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Circulating half life of PTH is?
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2-5 mins
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Where does PTH catabolism occur? (2)
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1. Kidneys
2. Liver |
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2nd messengers of PTH stimulation?
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cAMP & Ca
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PTH control of Ca, Mg & P ions through renal? (2)
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1. PTH stimulation of renal V3 secretion --> Absorption of Ca & P ions in GI
2. Stimulation of renal reasorption of Ca & excretion of P ions by kidneys |
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PTH control of Ca, Mg & P ions through bone? (2)
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1. Stimulate release of Ca & P ions from canaliculi fluid into ECF
2. Acts through receptors on osteoblasts, PTH stimulates bone resorption by osteoclasts to release Ca & P ions from bone into ECF |
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PTH stimulates bone formation that is coupled to?
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Bone resorption
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PTH increases synthesis of what by osteoblasts & down regulates what?
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Increases IGF-1
Decreases Sclerostin (which inhibits osteoblasts) |
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PTH stimulates synthesis of what by kidneys?
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Vitamin D3
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What stimulates parathyroid glands to produce PTH? (2)
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1 Decreased ECF Ca
2. Increased ECF K |
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What stimulates thyroid gland to produce calcitonin?
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Increased ECF Ca
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Calcitonin inhibits? (2)
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1. Bone breakdown
2. Parathyroid gland |
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PTH increases release of Ca & P ions from bone quickly by?
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Fast release= Osteocytic osteolysis
Ions in solution within canaliculi pumped out of bone |
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PTH increases release of Ca & P ions from bone slowly by?
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Bone breakdown by osteoclasts
PTH binds osteoblasts --> stimulate osteoclast differentiation & activity |
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What usually causes hyperparathyroidism? (3)
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1. Tumors
2. Vit D deficiency 3. Low dietary Ca |
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Symptoms of hyperparathyroidism? (4)
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1. High blood Ca & low P
2. Bone resorption 3. Decreased permeability of cells to ions 4. Urinary stones & soft-tissue calicification |
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Hypoparathyroidism caused by? (4)
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1. Atrophy of glands
2. Autoimmune disease 3. Accidental surgical removal 4. Mutations |
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Symptoms of hypoparathyroidism?
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Low blood Ca --> Increased nerve cell membrane permability & decreased membrane potentials --> Tetany
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How is Vit D3 acquired? (2)
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1. Ingested in diet
2. Synthesized in skin |
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How is Vit D3 synthesized in skin?
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1. 7-dehydrocholesterol --> pre-Vit D3 (photoconverted)
2. Pre-Vit D3 --> Vit D3 (spontaneous) |
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What happens to inactive Vit D3 produced by skin?
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Hydroxylated to 25-hydroxy D3 in liver
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What happens to 25-hydroxy D3 in kidney?
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PTH stimulates 1 alpha-hydroxylase to form active form of Vit D3
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What inhibits intestinal uptake of Ca & P? (3)
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1. Increased ECF phosphate
2. High levels of active D3 |
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Active vit D3 stimulates?
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Ca & P absorption from intestines
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What is calbindin?
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Ca binding protein which aids in Ca absorption once Ca is inside cells
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How is gene for synthesis of calbindin turned on?
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Active D3
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Other genes that active D3 stimulates? (5)
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1. Vit D receptor
2. Ca pump 3. Phosphate transporter 4. Osteocalcin 5. Alkaline phosphatase |
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Which genes are inhibited by active D3? (2)
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1. PTH
2. IL-2 |
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What are the direct effects of active D3 on bone?
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Helps PTH in multiplication & differentiation of osteoclasts & mobilize Ca out of bone
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What are the indirect effects of active D3 on bone?
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Increases Ca & P ECF through stimulation of intestine absorption, renal reabsopriton & mobilization from bone --> increases mineralization of bone osteoid
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As concentration of P ions increase Ca concentration will?
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Decrease
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Ca & PO4 in blood form?
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Calcium phosphate= insoluble
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