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unit 6: physiology > parathyroid hormone (12) > Flashcards

parathyroid hormone (12) Flashcards

(58 cards)

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1
Q

what is the total amount of calcium in the body? (in mg/dL)

A

9-10.6 mg/dL

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2
Q

in mg/dL what is amount of ionized calcium in the body?

A

4.05-5.2 mg/dL

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3
Q

what calcium value is typically measured in blood tests?

A

total calcium

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4
Q

what are the two forms of calcium found in the blood?

A

protein bound- 40%

ultra filtrable- 60%

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5
Q

what two groups can the “ultafilterable” be broken into?

A

complexed to anions- 10%

ionized calcium 50%

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6
Q

what percentage of calcium in the body is in the ECF and muscles?

A

only 1% !!

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7
Q

what percentage of calcium in the body resides in the plasma (extracellularly)?

A

.1%!! and half of that is ionized

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8
Q

if a person has a higher than normal albumin level, how can this affect measuring their calcium levels?

A

it can cause a high calcium which would be a false positive when in reality ionized calcium can be totally normal (and this is what you really care about)

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9
Q

what effects can acidemia have on ionized calcium?

A

it can cause albumen in the plasma to bind LESS calcium leading to a TRUE increase in ionized calcium

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10
Q

what are some symptoms of hypercalcemia? what value in mg/dL is considered hypercalcemia?

A

> 12 mg/dL
fatigue, apathy, anorexia, delirium, coma, headache, increase intracranial pressure,
high calcium concentration will increase membrane polarization and reduce neural response

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11
Q

what are some symptoms of hypocalcemia? what value in mg/dL is considered hypocalcemia?

A

<7mg/dL
leading retardation, apnea (children
tetany, numbness, muscle cramps
low calcium concentration will reduce the membrane polarization and increase hypersensitivity

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12
Q

what 3 organ systems are involved in maintaining a normal “calcium economy”

A

digestive system
kidneys
bone

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13
Q

what percentage of our ingested calcium in excreted in the feces?

A

80%

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14
Q

what role does the kidney play in calcium balance?

A

filters 10x the average daily intake and recaptures almost all of it (175mg/day is excreted in urine)

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15
Q

what is the turnover of bone in adults per day?

A

280 mg/day

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16
Q

what two key hormones control calcium homeostasis?

A

vit D and PTH

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17
Q

what will be the effect of binding of PO4 to calcium?

A

it will reduce the ionized calcium level

it tends to “buffer” the calcium concentration

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18
Q

what gland produces calcitonin?

A

thyroid gland

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19
Q

what is the function of calcitonin?

A

inhibits bone resorption

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20
Q

describe the effects of PTH on the kidney

A

rapid effects

  • increases calcium by increasing re-abosorption in the distal tubule
  • decrease PO4 by reducing re-absorption in the proximal tubules
  • increase 1,25 (OH) D3 synthesis
  • increase urinary cAMP
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21
Q

what is the effects of PTH on the bone cells?

A

increase osteoCLASTIC resorption via receptors on the osteoblasts–>this increase calcium and PO4 in the ECF and plasma

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22
Q

what cells secrete RANK-L?

A

osteoblasts

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23
Q

what is the effect of RANK-L on monocyte lineage cells?

A

causes their maturation into active multinucleated osteoclasts

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24
Q

what cells release PTH?

Study These Flashcards
A

chief cells of the parathyroid gland

25
how does low calcium trigger the release of PTH?
calcium sensing receptor is a G protein coupled receptor with a signaling cascade involving intraceullar calcium binding/releasing from the ER
26
what is familial hypercalcemic hypocalcuria (HFF)?
caused by mutation in the calcium sensing receptor gene there is increase tubular re-absorption of calcium these ppl's "normal calcium" levels will be high but they will not have symptoms
27
what percentage of daily calcium is re-absorbed at the proximal tubule? distal tubule? what about the rest?
proximal tubule- 60% distal tubule- 9% the rest of the calcium is re-absorbed via passive diffusion in most other locations
28
what part of the kidney does PTH act to increase ca++ re-absorption?
distal tubule
29
what are the 4 targets of vitamin D?
intestine bone parathyroid gland kidney
30
what are the effects of vit D on PTH?
tends to reduce PTH production in the parathyroid gland | does this to act as a buffer to make sure correcting the low calcium doesn't get out of control
31
what is a marker for bone turnover that can be seen in a parathyroid adenoma?
alkaline phosphatase
32
What is the cause of high serum calcium in Humoral Hypercalcemia Malignancy?
The release of PTH- related peptide by tumors. THe PTH-rp activates the same receptors as PTH, which causes serum Ca++ to increase
33
What is the cause of secondary hyperparathyroidism?
Hypocalcemia is primary cause (due to low vit D, renal failure, diet)
34
What is psuedohypoparathyroidism?
Hypocalcemia due to a genetic defect in the G protein in PTH receptor in kidney
35
What is the cause of Familial hypocalciuric hypercalcemia?
genetic defect in Ca++ sensors, which increases Ca++ reabsorption
36
Normal plasma range of Phosphorus? How much is bound to protein?
2.5-4.5 mg/dL. 10-20% is bound to protein.
37
What cells line the bone surfaces and actively synthesize bone?
OsteoBlasts
38
Describe how collagen is matured?
Precursor molecules of collagen are synthesized in the cell and exported attached as telopeptides. Outside the cell the collagen molecules further polyerize in a crystalline arrangement to forms long fibrils.
39
What is found between the layer of osteoBlasts and the mineralizing matrix?
Osteoid, this is not yet mineralized collagen
40
What is the osteoid a indication for?
The state of health of the skeleton and the availability of Ca and PO4
41
Which cells do most of the signalling in the bone?
OsteoBlasts
42
What do osteoblasts have receptors for?
PTH, Vit D, Estrogen, many paracrine factors and growth factors
43
What comprises the weight of the bone?
Bone Mineral 65% Collagen 22% Fluid 10% Non-collagenous proteins and cells 1-2%
44
How does bone mineralization begin?
Microcrystalline HA mineral deposition in collagen matrix. Crystals begin to form in "hole" regions.
45
What are the two methods of bone remodeling?
1- Osteonal Tunneling 2- Surface Remodeling
46
Describe osteonal tunneling?
Occurs in cortical bone, osteoclasts drill through the bone and osteoblasts follow and lay down bone. Haversian canals result from this action.
47
Describe Surface remodeling?
Occurs in trabecular bones. Osteoclasts breakdown bone and steoblasts replace and new bone forms. This liberates a lot of Ca++ and PO4.
48
What allows for osteoclats to mature an be activated?
A cytokine from the osteoblast lineage cells called RANK-L
49
What does RANK-L bind to?
RANKs (on osteoclasts and precursor cells)
50
What competitively inhibits RANK-L?
OPG which is a soluble substance produced by osteoBlasts
51
What are the effects of estrogen on bone remodeling?
Reduces reabsorption
52
What are the effects of calcitonin on bone remodeling?
Transient inhibitor of osteoclasts
53
Do glucocorticoids inhibit or enhance intestinal Ca absorption?
Inhibits
54
How does mechanical loading effect bone remodeling?
Locally promotes cone accrual and maintenance
55
What are the elements of the bone that are most sensitive to mechanical loading? What is the action of these elements?
Osteocyte and its connected canaliculae work to reduce the expression of sclerostin
56
What is sclerostin?
An inhibitor of bone formation mediator when bone loading is weak.
57
What is osteoporosis?
Related to disease or aging...it is inappropriate or excessive remodeling
58
What is osteopenia?
Substantial bone loss but not enough to be in danger of fracture.

unit 6: physiology (13 decks)

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