Term
| What is the usually plasma calcium concentration? |
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Definition
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Term
| What is the biologically active form of calcium? |
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Definition
Ionized calcium
50% of plasma calcium is ionized |
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Term
| How does blood pH affect ionized calcium? |
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Definition
An increase in plasma pH decreases the quantity of ionized calcium by increasing protein-bound calcium
This occurs during respiratory alkalosis seconday to hyperventilation and causes neuromuscular irritability, tetanic muscle contractions in hands and feet, seizures and muscle spasms of the larynx |
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Term
| What is the daily calcium intake? |
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Definition
1000 mg
800 mg are excreted in the feces, 200 mg are excreted in urine |
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Term
| What is the plasma concentration of phosphorus? |
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Definition
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Term
| What is the plasma range for magnesium? |
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Definition
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Term
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Definition
| Calcium phosphate compound that impregnates collagen matrix to form bone |
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Term
| What receptors do osteoblasts express? |
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Definition
| Receptors for PTH and Vit D3 |
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Term
| What receptor types are expressed by osteoclasts? |
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Definition
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Term
| Osteocytes express receptors for what? |
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Definition
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Term
| What is osteocytic osteolysis? |
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Definition
| The transfer of calcium from the interior to the exterior of bone units through canaliculi |
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Term
| What are the main effects of Vit D3 |
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Definition
Calcium absorption in the gut and bone resorption
Main role is to remodel bone |
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Term
| If calcium levels are low, the kidney mitochondria will synthesize more of what enzyme? If calcium levels are high, which enzyme will be produced more? |
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Definition
Low calcium: 1-hydroxylase
Makes 10 fold more active vit D
High calcium - 24-hydroxylase
Makes inactive vitD |
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Term
| Vit D recptors for a heterodimer with what other receptor? |
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Definition
| Retinoid X receptor (RXR) |
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Term
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Definition
They promote calcium absorption from the intestinal lumen against the concentration gradient
Vit D stimulates calbindin synthesis in the villus and crypt cells of the intestine |
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Term
What are the main actions of PTH?
What inhibits PTH? |
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Definition
Increase plasma calcium concentrations
Decrease phosphate concentrations
PTH gene transcription, secretion and parathyroid glandular proliferation are inhibited by Vit D |
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Term
| What cells produce calcitonin? |
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Definition
| Parafollicular cells (C cells) of the thyroid |
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Term
| What stimulates calcitonin secretion? |
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Definition
| Ingestion of food, due to gastrin |
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Term
| True or False: Calcitonin deficiency causes hypercalcemia |
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Definition
False
The body readjusts the levels of PTH and vit D to accomodate the absence of calcitonin |
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