Calcium Homeostasis


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  • Created by: emma
  • Created on: 09-12-13 14:18
Hypocalcium increases nerve excitability.. leading to
tetany --> asphyxiation
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Hypercalcaemia decreases neurotransmitter excitability... leading to
cardiac arrhythmias, lethargy, death
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3 causes of hypercalcaemia
54% hyperthyroidism, 34% malignancy associated, 12% other
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3 ways homeostasis is maintained
Bone - 500mg. Kidney, 10.8 filtration, 10.6 reabsorption. Intestines, 1g diet, 800mg faeces.
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Free ionised calcium = ?mM
1.2 mM
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sensing mechanisms sense changes in...
Free ionised calcium levels
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Where is PTH produced
Chief cells in Parathyroid gland
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Where is PTH cleaved
Liver
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PTH secretion is ? proportional to serum calcium
inversely - signmoidal
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Effects of VitD
increase net intestinal Ca uptake from 200-600 mg/day, increase calbindin expression, increase serum Ca levels by increased bone resorption and renal reabsorption
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Deficiency of Vit D can cause
Rickets, secondary HPT and osteomalacia
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Where is calcitonin produced
parafollicular thyroidal c cells
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what calcitonin do?
decrease calcium after load
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Oral calcium salts are..
calcium gluconate, calcium lactate, hydroxyapatite
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injected calcium salts are
calcium gluconate for hypocalcaemia tetany
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Oral vitamin D3...
t1/2=22hours, binds alpha globulin, treats rickets, osteodystrophy and HPT hypocalcaemia
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Excess VitD3 can cause
hypercalcaemia, osteoporosis, proteinuria, polyuria, nephrocalcinosis, vascular cacification
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To treat hypercalcaemic crisis..
saline hydration, furosemide (Lasix) diuresis (Decrease calcium reabsorption in cTAL), calcitonin (decrease bone resorption) and bisphosphonates
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Glucocorticoid treatment
decreases intestinal ca absorption, decreases bone foration, increases renal extretion, may lead to osteoporosis
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disphosphonates
decrease bone turnover, bind hydroxyapatite
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mithramycin
decrease bone reabsorption, antibiotic in cancer treatment, treat hypercalcaemia and paget's at 1/10 of chemo dose
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calcimimetics
decreases PTH secretion, treats primary and secondary HPT, +VE allosteric modulator of CR
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calcilytics
increase PTH secretion, osteoporosis treatment, -ve allosteric modulator of CR (antagonist)
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sodium cellulose phosphate
oral, binds ca in gut, decreases intestinal absorption, may increase serum phosphate
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Card 2

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Hypercalcaemia decreases neurotransmitter excitability... leading to

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cardiac arrhythmias, lethargy, death

Card 3

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3 causes of hypercalcaemia

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Preview of the front of card 3

Card 4

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3 ways homeostasis is maintained

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Card 5

Front

Free ionised calcium = ?mM

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