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30 Cards in this Set
- Front
- Back
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What element is the major extracellular divalent cation?
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Ca++
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What % of calcium in a normal adult man and woman is found in the bone?
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99% is in the bone
Normal man - 1300g Normal woman - 1000g |
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All cells contain how much Ca++?
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0.1 microMolar
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What is Ca++ essential for in the body?
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Neuronal excitability
neurotransmitter release muscle contraction membrane integrity blood coagulation 2nd messenger in hormone actions (Ca++-ATPase) |
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What % of calcium in plasma is bound to proteins and what % is complexed with anionic buffers? What does the remaining percentage do?
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40% is bound to proteins, albumin, in plasma
10% is complexed with anionic buffers, such as phosphate The remaining 50% exerts physicological effects and can produce hypocalcemic symptoms when reduced |
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What form of calcium is found in the skeleton?
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crystalline form resembling hydroxyapatite Ca10(PO4)6(OH)2
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True or False: 75% of dietary calcium is obtained from milk and dairy products?
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True
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What is the adequate calcium intake for adolescents, adults, and people over 50 years
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Adolescents: 1300mg/day
Adults: 1000mg/day Over 50: 1200mg/day |
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Calcium enters the body through the intestine by what 2 mechanisms?
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1) active vitamin D-dependent transport in the proximal duodenum
2) facilitated diffusion throughout small intestine |
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Reabsorption of calcium is highly regulated by what hormone?
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Parathyroid hormone (PTH)
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Intestinal calcium absorption efficiency is inversely related to what?
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calcium intake
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What drugs can depress intestinal calcium transport?
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glucocorticoids and phenytoin
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What is bone remodeling?
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A continuous breakdown and renewal that continues through life
- carried out by individual bone modeling units |
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In which bones is bone remodeling most active?
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"Central" bones such as the pelvis (large bones)
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How is calcium released by osteoclasts? How do osteoblasts rebuild this bone?
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Osteoclast production is regulated by cytokines produced by osteoblasts
- the osteoclasts release HCl to resorb, or dig a cavity into the bone to release Ca++ Osteoblasts secrete proteins (collagen and calcitonin) into this cavity - osteoid (soft, gel-like substance) is used to fill the small holes - about 10 days later it becomes hard and mineralized |
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What is the bone made up of to provide strength and elasticity?
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Collagen - elasticity
CaPO4 - strength |
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How do ODF (RANK ligand) and OPG play a role in bone remodeling?
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*ODF (osteoclast differentiation factor) is released by osteoblasts and binds to RANK on osteoclasts to stimulate production
*OPG is produced by osteoblasts to inhibit RANK |
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Circle correct choice:
When estrogen is sufficient, OPG INCREASES/DECREASES, preventing ODF from binding to rank and INCREASING/DECREASING osteoclasts |
INCREASES; DECREASING
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How long does it take for the completion of a remodeling cycle?
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6 months
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Three things that are important for bone remodeling and maintenance:
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exercise
estrogen Ca++ |
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Do theses groups decrease or increase bone remodeling?
PTH, vitamin D, TH, and GH Testosterone and estrogen |
PTH, vitamin D, TH, and GH: increase bone remodeling
Testosterone and Estrogen: decrease bone remodeling |
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If parathyroid glands are accidentally removed with removal of thyroid gland, what happens to calcium levels?
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Calcium levels drop too low, leading to seizures and involuntary muscle contraction
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Where does the conversion of preproPTH to PTH occur?
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in the ER and Golgi complex
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Why does PTH 7-84 (a variation of PTH in amino acid size) develop in certain patients?
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It develops with kidney problems because PTH will no longer bind to receptors in the kidney.
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What is the primary function of PTH?
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to elicit adaptive changes that maintain a constant concentration of calcium in extracellular fluid
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In normal pts, most PTH is degraded before it is secreted. What happens in hypocalcemia?
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More PTH is secreted and less is degraded.
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What does PTH regulate through the G protein-coupled receptors, PTH-1 and PTH-2?
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Intestinal Ca++ absorption
mobilization of bone Ca++ excretion of Ca++ in urine and feces |
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When plasma Ca++ is low, PTH secretion ??
When plasma Ca++ is high, PTH secretion ?? |
When Ca++ is low, PTH secretion increases
When Ca++ is high, PTH secretion decreases |
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What is PTH's effect on bone resorption, Ca++, kidneys, and vitamin D?
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*PTH increases overall bone resorption and increases the delivery of Ca++ to extraellular fluid.
*PTH acts on kidney to enhance efficiency of Ca++ reabsorption, to inhibit phosphate reabsorption, to stimulate conversion of vitamin D to its hormonal form, calcitriol |
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Teriparatide (Forteo): indication, dose, and effect
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PTH (1-34)
Indication: osteoporosis in men and postmenopausal women Dose: 20microgram/day injection Effect: increases bone mass |
