Term
1. What is the amount of intracellular Ca+?
2. What is the amount of extracellular Ca+? |
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Definition
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Term
| What maintains the large Ca+ gradient? |
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Definition
| Cell Membrane and Ca+pumps. |
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Term
| What is the biologically active form of Ca+? |
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Definition
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Term
1. What is the effect of an increase in plasma pH with respect to ionized calcium concentration?
2. What does this cause physiologically? |
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Definition
It decreases since raised pH increases protein-bound calcium.
2. Causes neuromuscular irritability, tetanic contractions, and muscle spasms of the larynx that can obstruct the airway. |
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Term
| Nerves exposed to ________ concentrations of exhibit lower thresholds of excitation. |
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Definition
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Term
| What is "readily exchangeable" calcium? |
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Definition
| This is calcium that is at the surface of recently or partially mineralized bone. It amount to 4000 mg. |
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Term
| What is the role of phosphate in the body? |
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Definition
| It is a critical component of high-energy compounds such as ATP, creatine phosphate, NADP, etc... |
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Term
| Where is most of the phosphate in the body stored? How much does it amount to? |
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Definition
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Term
What is Magnesium essential for?
What is the total amount in the body? |
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Definition
Neuromuscular Transmission and often serves as a cofactor
~25 g: 12.5 g in the skeleton and 12.5 g in the intracellular fluid |
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Term
1. What is cortical bone?
2. What is trabecular bone?
3. What is the percentage of each in bone? |
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Definition
1. Compact bone, long, flat bone
2. Interior shafts of long bones, bone spicules
3. Coritical - 80%
Trabecular - 20% |
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Term
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Definition
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Term
| Bone is formed from collagen matrix impregnated with the calcium phosphate compound, _______. |
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Definition
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Term
| What is the bone remodeling unit? |
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Definition
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Term
| What are the bone forming elements and where do they derive from? |
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Definition
| Osteoblasts. Dervied from osteoprogenitor cells. |
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Term
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Definition
| The matrix for developing bone |
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Term
| What are the bone resorbing elements and what do they derive from? |
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Definition
| Osteoclasts, which derive from macrophages. |
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Term
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Definition
| Osteoblasts that have become surrounded by a calcified matrix. They exhibit a decreased synthetic activity. |
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Term
| How do osteocytes maintain connections between neighboring osteocytes? |
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Definition
| Via canaliculi, fluid-containing channels within the bone structure. |
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Term
| What receptors do osteoblasts express? |
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Definition
| PTH and 1,25-(OH)2-Vitamin D3 |
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Term
| What receptors do osteoclasts express? |
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Definition
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Term
| What receptors do osteocytes express? |
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Definition
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Term
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Definition
| A protein that is bound to collagen that forms complexes with hydroxyapatite crystals |
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Term
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Definition
| A protein that has a high affinity for uncrystalized hydroxyapatite and binds calcium through its gamma-carboxyglutamate groups. |
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Term
| What do osteoclasts use to breakdown bone? |
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Definition
| Lysosomal enzymes that acidify the local environment, phosphatases, and collagenase. |
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Term
| What is the role of Vitamin D with respect to calcium? |
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Definition
| It sitmulates calcium absorption in the gut and bone resorption. It works to increase the plasma calcium concentration. |
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Term
| What converts cholesterol analogs into previtamin D3? |
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Definition
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Term
How does Vitamin D3 circulate in the blood?
Where is excess Vitamin D3 stored? |
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Definition
| Bound to α-globin. Excess is stored in the liver and in fat. |
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Term
| What is the active metabolite of Vitamin D3? |
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Definition
| 1,25-(OH)2-Vitamin D3. It is 10 fold more active than regular Vitamin D3 |
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Term
| Where is 1,25-(OH)2-Vitamin D3 formed? |
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Definition
| In the kidney mitochondria by an 1-α-hydroxylase. This enzyme is most active when concentrations of 1,25-(OH)2-Vitamin D3 are low. |
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Term
| What is the action of 1,25-(OH)2-Vitamin D3? |
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Definition
| Binding of 1,25-(OH)2-Vitamin D3 results in synthesis of calbindins in the villus and crypt cells that increases the absorption of calcium int he gut. |
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Term
| What is the action of Parathyroid Hormone? |
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Definition
| Pulsitile action that increases calcium concentrations by stimulating bone resorption, renal tubular reabsorption, and 1,25-(OH)2-Vitamin D3 synthesis. |
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Term
| PTH secretion is _______ related to the plasma ionized calcium concentration. |
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Definition
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Term
| T/F: 1,25-(OH)2-Vitamin D3 inhibits PTH synthesis. |
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Definition
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Term
| What is the action of PTH on the osteoblasts, osteocytes, and osteoclasts? |
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Definition
Osteoblasts - Decreases synthesis of collagen
Osteocytes - increase osteolysis
Osteoclasts - increase resorption and proliferation
All act to increase the calcium serum levels |
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Term
| Where is calcitonin released from? |
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Definition
| From the C-Cells (Parafollicular) of the Thyroid |
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Term
| What is the action of calcitonin? |
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Definition
Lowers blood plasma concentration, promotes detachment of osteoclasts from bone surface, decreases bone resorption resulting in denser bones.
Plasma phosphate levels will decrease |
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Term
How do plasma phosphate levels respond to PTH?
To calcitonin? |
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Definition
| They drop in both instances. With PTH, reabsorption in the kidneys is decreased to ensure excess phosphate from bone resorption is eliminated. With calcitonin, the levels drop with increased bone development and decreased kidney reabsorption. |
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Term
| Which has a faster response to PTH, gut or kidney? |
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Definition
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Term
What is the manifestation of hyperparathyroidism on calcium levels?
Hypoparathyroidism? |
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Definition
Hypercalcemia
Hypocalcemia |
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