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Physiology II Exam 2 (Lauren) > L19-20 Calcium And Phosphate Regulation > Flashcards

L19-20 Calcium And Phosphate Regulation Flashcards

1
Q

Free calcium fluctuates (hardly at all/a lot)

A

Hardly at all. Changes less than 2%

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2
Q

99% of calcium in your body is in what form?

A

Crystalline form in teeth and bone

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3
Q

If you eat 1000mg of calcium, how much do you poop and pee out that day?

A

1000mg

(You absorb about 350 mg, but you also secrete 350mg of your body’s calcium back into the intestine and urine. Plus 650mg from diet didn’t even get absorbed)

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4
Q

How much of plasma calcium is in the ionized active form

A

50%

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5
Q

What is the normal plasma concentration of calcium

A

10mg/dL

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6
Q

What is required to absorb calcium from the intestine and from the bone

A

1,25-Dihydroxycholecalciferol aka Vitamin D

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7
Q

What effect does calcitonin have on bone resorption?

A

Inhibits it

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8
Q

What are the target organs of parathyroid hormone

A

Bone

Intestine

Kidney

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9
Q

What causes PTH to be released

A

DROP IN BLOOD CALCIUM*****

PTH then acts on kidney, bone and intestine to normalize blood calcium levels

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10
Q

What cells in the parathyroid release PTH?

A

Chief cells**

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11
Q

Does the parathyroid have any follicular cells

/

A

No

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12
Q

What is the effect of PTH on vitamin D?

A

Promotes the activation of Vitamin D to increase calcium absorption from food

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13
Q

What is the affect of PTH on bone

A

Activated osteoclasts to release calcium and phosphate into blood

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14
Q

What are the 2 calcium pools in your bones?

A

Stable pool

Labile pool

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15
Q

What kind of bone is in the stable pool?

A

Mature mineralized bone composed primarily of hydroxyapatite

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16
Q

What kind of bone is in the labile pool?

A

Bone fluid composed primarily of amorphous crystals

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17
Q

Which pool releases calcium And phosphate into the blood faster?

A

Labile pool

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18
Q

Which pool would your body use if you needed to make a quick small adjustment to blood calcium

A

Labile pool

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19
Q

How do calcium and phosphate get from the labile pool into the blood

A

The pool undergoes osteolytic osteolysis and then there is a rapid exchange with the ECF

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20
Q

Within the bone, what separates the bone itself from the plasma within the canals?

A

Ostocytic-osteoblastic bone membrane

This has a large surface area and a small movement of calcium= large influx of calcium and phosphate into the plasma from the bone fluid

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21
Q

What are the 2 effects of PTH on the kidney?

A
  1. Stimulates calcium reabsorption
  2. Inhibits PO4 reabsorption

(Calcium IN, Phosphate OUT)

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22
Q

Elimination of PO4 in the kidney also causes what other substance to increase in the urine?

A

Urine cAMP

because you need cAMP to eliminate PO4

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23
Q

What lab value could you measure to track a patient’s PTH status?

A

cAMP levels in the urine

increase PTH= increased cAMP in the urine

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24
Q

How does PTH activate vitamin D?

A

Stimulates 1-α hydroxylase activity in the kidney

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25
What are the 2 steps required for vitamin D to become activated?
1. Addition of (OH) on carbon 25 in the liver via the enzyme 25-hydroxylase 2. Addition of (OH) on carbon 1 in the kidney via the enzyme 1α-hydroxylase Results in 1,25-dihydroxycholecalciferol ***STEP 2 ONLY HAPPENS IF YOU DON’T GET ENOUGH CALCIUM FROM YOUR DIET*****
26
Is vitamin D3 considered a prohormone?
Yes
27
What are the 2 names for active vitamin D3
1,25-dihydroxyvitamin D3 1,25-dihydroxycholecalciferol
28
If you have an adequate amount of calcium in your diet, what happens to the Vitamin D3 you eat/your skin makes
1. Vitamin D3 goes to Liver. 2. (OH)group is added to carbon 25 by 25-hydroxylase 3. Goes to kidney 4. (OH) group is added to carbon 24*** 5. Produces inactive 24,25-dihydroxycholecalciferol
29
What effect does Vitamin D have on the bones?
It synergizes with PTH to remodel the bone and to mobilize calcium and PO4.
30
True or false: | Vitamin D + PTH are required for bone growth
True
31
What effect does vitamin D have on the kidney?
Reabsorption of calcium Reabsorption of Phosphate**!!! (It has the opposite effect on PO4 reabsorption as PTH)
32
What effect does Vitamin D have on the small intestine?
It makes more Calbindin, which then allows the body to absorb more calcium from the diet
33
What is calbindin
It is inside small intestine cells and it absorbs calcium out of the foods you eat
34
What effect do glucocorticoids have on PTH?
They increase PTH secretion | Too much corticosteroids= lots of bone resorption=fracture risk
35
Type II diabetics and obese people have lots of cortisol. Why does this put them at in increased fracture risk?
Corticosteroids increase the secretion of PTH which can cause too much bone resorption and put them at risk
36
What effect does Vitamin D have on PTH secretion?
Decreases it
37
What are the possible risks of taking too much vitamin D?
Fracture risk Hypercalcemia
38
What does calcitonin do?
Decreases plasma calcium and PO4
39
How does calcitonin decreases plasma Calcium and PO4?
Inhibits bone resorption Inhibits tubular reabsorption in Kidney
40
What effect does calcitonin have on the intestine?
NONE*!!!**!!
41
Calcitonin does the opposite of PTH except in what organ?
In the small intestine. PTH causes increased calcium reabsorption Calcitonin has NO EFFECT on the small intestine.
42
What causes calcitonin release?
Increased plasma calcium
43
Why do we have calcitonin
We dont really know - when we don’t have calcitonin, we don’t get hypercalcemia - excessive calcitonin does not produce hypocalcemia - may prevent hypercalcemia after a meal?
44
What is the only time we think calcitonin might have an important role?
In pregnancy
45
What disease: | “Stones, bones and groans”
Primary hyperparathyroidism
46
What is the most common cause of primary hyperparathyroidism?
A PTH-secreting tumor
47
If your patient has primary hyperparathyroidism, what do you expect to see in Plasma: Urine:
Plasma; hypercalcemia and hypophosphatemia Urine: increased phosphate, cAMP, and hypercalciuria
48
What are the complications of hyperparathyroidism?
Muscle weakness **** Kidney stones Osteoporosis, ostemalacia (bones) Constipation (groans)
49
What causes hypoparathyroidism?
Thyroid surgery
50
What is Trousseau’s Sign and in what condition might you see it?
It is spasms of the hand when you inflate a BP cuff around the arm. Seen in hypoparathyroidism (low calcium)
51
Low calcium causes muscle (weakness/hyperactivity)
Hyperactivity
52
If you have a tumor that is secreting PTH-related peptide, what will happen to calcium and phosphate levels?
Hypercalcemia Hypophosphatemia (Same thing as if it was real PTH)
53
If you have a tumor that is secreting PTH-related peptide, what will PTH levels be?
Low**** | PTH secretion is inhibited by hypercalcemia
54
“PTH resistance” describes what condition?
Pseudohypoparathyroidism aka Albright’s hereditary osteodystrophy
55
What is pseudohypoparathyroidism?
An autosomal dominant disorder where PTH binds to its receptor, and then nothing happens due to defective signal transduction
56
In pseudohypoparathyroidism, what are the levels of: PTH: Calcium: Phosphate:
PTH: high Calcium: low Phosphate: high
57
What will someone with pseudohypoparathyroidism look like?
Short Short neck Obese Short 4th finger and 4th toe
58
Primary hyperparathyroidism effect on: PTH: Vitamin D: Bone resorption: Urine: Calcium: Phosphate:
PTH: high Vitamin D: high (effect on 1α-hydroxylase) Bone resorption: high Urine: high PO4, Ca, and cAMPT Calcium: high Phosphate: low
59
Surgical hypoparathyroidism effect on: PTH: Vitamin D: Bone resorption: Urine: Calcium: Phosphate:
PTH: low Vitamin D: low (effect on 1α-hydroxylase) Bone resorption: low Urine: low PO4 and cAMP Calcium: low Phosphate: high
60
Pseudohypoparathyroidism effect on: PTH: Vitamin D: Bone resorption: Urine: Calcium: Phosphate:
PTH: high Vitamin D: low Bone resorption: low Urine: low PO4 and cAMP Calcium: low Phosphate: high
61
``` Humoral hypercalcemia (tumor that secretes PTH-related peptide) effect on: PTH: ``` Vitamin D: Bone resorption: Urine: Calcium: Phosphate:
PTH: Low Vitamin D: no effect**** calcium uptake not increased in presence of PTH-rp Bone resorption: high Urine: increased PO4, Ca, and cAMP Calcium: high Phosphate: low
62
What causes rickets?
Deficiency of vitamin D in childhood
63
What is osteomalacia?
Deficiency of vitamin D in adulthood | Either due to diet or intestinal surgery that affects absorption
64
What muscle effects would you expect to see in rickets or osteomalacia?
Hypocalcemic Tetany
65
Why would low vitamin D cause you to break your bones a lot (rickets/osteomalacia)
No vitamin D= no calcium absorption and high levels of PTH due to the hypocalcemia = bone resorption

Physiology II Exam 2 (Lauren) (4 decks)

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