lecture 23- calcium balance Flashcards
what does an increase in calcium above normal cause in the nervous system
progressive depression of nervous system
what does a decrease in calcium concentration do to the nervous system
it becomes more excited
how do large changes in level of phosphate in extracellular fluid effect the body
no major immediate effects
how do slight changes in extracellular calcium effect the body
cause extreme immediate physiological effects
where does the first sign of tetany with hypo calcium typically occur
in the hands
why does the nervous system become progressively more excited during hypocalcemia
due to increased neuronal membrane permeability to sodium ions
______ percent of the plasma calcium bound to plasma proteins is not filtered by glomerular capillaries
41
what does the precipitation of calcium along the collagen fibers eventually forms _______
hydroxyapatite crystals
when do calcium salts precipitate in other tissues
when the inhibitor factors that normally prevent deposition of calcium salts disappear from the tissues
what is the active form of vitamin D
1,25-dihydroxycholecalciferol
what type of binding domains does the vitamin D receptor have
hormone-binding and DNA-binding domains
what is the function of calbindin
functions in the brush border of the epithelial cells to transport calcium into the cell cytoplasm
what happens to the effect of PTH when vitamin D is absent
effect of PTH is reduced
what does vitamin D in small quantities promote
bone calcification
how does vitamin D in small quantities promote bone calcification
by increasing calcium and phosphate absorption from the intestines
what does excess activity of the parathyroid gland result in
hypercalcemia in extracellular fluid
where does the synthesis of PTH occur
ER and golgi
T/F: osteoclasts of membrane receptor domains for PTH
FALSE
what are the 2 stages of activation of the osteoclastic system
- immediate activation of the osteoclasts that are already formed and 2. formation of new osteoclasts
what happens when the of effect of PTH on the kidneys to increase calcium reabsorption is lost
the urine would eventually deplete both the extracellular fluid and the bones of calcium
what is a large share of the effect of PTH on its target organs mediated by
cAMP
what conditions decrease calcium ion concentration
rickets, pregnancy and lactation
what is calcitonin secreted by
thyroid gland
what does calcitonin tend to do to the plasma calcium concentration
decreases
what happens to osteoclastic activity with paget disease
it is greatly accelerated
