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Physiology > Regulation of Calcium and Phosphate Metabolism > Flashcards

Regulation of Calcium and Phosphate Metabolism Flashcards

1
Q

What are the processes in which Ca is involved?

A
  • neurotransmission
  • learning and memory
  • muscle contraction
  • mitosis
  • mobility
  • secretion
  • fertilization
  • blood clotting
  • structure of bones and teeth
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2
Q

What makes up the regulatory system to maintain extracellular fluid levels of Ca and P?

A
  • vitamin D
  • parathyroid hormone
  • calcitonin
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3
Q

Describe extracellular Ca levels.

A
  • higher Ca concentration
  • 50% ionized (free), 40% bound, 10% complexed in other forms(anions)
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4
Q

Describe intracellular Ca levels.

A
  • lower Ca concentration
  • cystolic Ca can be increased as needed
  • some Ca bound to proteins
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5
Q

Explain Ca balance.

A

If Ca intake goes down, body adjusts by increasing percentage of Ca absorbed

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6
Q

Ca-sensing is done by what receptors involved in Ca homeostasis?

A

Ca receptors on endocrine cells

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7
Q

What is hypocalcemia and its effects?

A
  • decrease in plasma Ca (ionized Ca)
  • causes twitching/cramping of skeletal muscle
  • can cause numbness/tingling (paresthesia), seizures if extreme
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8
Q

What can cause hypocalcemia?

A
  • lactation
  • parathyroid disorders
  • vitamin D disorders
  • gut malabsorption of Ca
  • renal failure
  • ethylene glycol toxicity
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9
Q

What is hypercalcemia and its effects?

A
  • increase in plasma Ca (ionized Ca)
  • causes constipation, polyuria, polydipsia, lethargy, coma, death
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10
Q

What can cause hypercalcemia?

A
  • parathyroid disorders
  • vitamin D toxicity
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11
Q

What can result in altering forms of Ca in plasma?

A
  • changes in plasma protein concentration
  • changes in complexing anion concentration
  • acid-base disutrbances
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12
Q

What occurs during acidemia?

A
  • more H ions in blood
  • more H ions bind to albumin
  • free ionized Ca increases which leads to hypercalcemia
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13
Q

What occurs during alkalemia?

A
  • less H ions in blood
  • more Ca bind to albumin
  • ionized Ca in blood decreases which leads to hypocalcemia
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14
Q

Intestinal absorption of Ca is regulated by what?

A

vitamin D

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15
Q

Kidney reabsorption of calcium is refulated by what?

A

PTH

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16
Q

Why can Ca be released into or absorbed from blood?

A

Because bone is constantly remodeled

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17
Q

Describe calcium homeostasis.

A

interaction of bone, kidney, and intestine, plus parathyroid hormone, calcitonin, and vitamin D

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18
Q

What substances stimulate bone reabsorption of Ca?

A
  • parathyroid hormone
  • vitamin D
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19
Q

What substance inhibits bone reabsorption of Ca?

A
  • calcitonin
20
Q

Where is phosphate stored?

A

muscle

21
Q

What ion has a fairly constant absorption from diet?

A

phosphate

22
Q

Which substance is necessary for neuromuscular transmisison?

A

magnesium

23
Q

What substance is a cofactor in enzyme reactions?

A

magnesium

24
Q

Dietary megnesium absorbed by the gut is enhances by what?

A

vitamin D

25
Q

What hormone regulates plasma Ca and P?

A

Parathyroid hormone

26
Q

What cells are the source of PTH from the parathyroid glands?

A

chief cells

27
Q

What are stimulators of PTH release?

A
  • decreased blood Ca
  • increased blood phosphate
  • decreased Mg
28
Q

PTH stimulates what, which ultimately feeds back and decreases PTH secretion?

A

vitamin D

29
Q

What inihbits PTH release?

A

increased blood Ca

30
Q

PTH targets what tissues?

A
  • bone
  • kidneys
  • intestines
31
Q

What are the actions of PTH?

A
  • increases bone resorption to release Ca and P into blood
  • stimulates Ca reabsorption in distal convoluted tubule of kidney
  • inhibits phosphate reabsorption in proximal convoluted tubules of kidneys, thus causing P excretion in urine
  • increases Mg reabsorption in kidneys
  • stimulates vitamin D synthesis in kidneys
  • increases Ca absorption from intestine via vitamin D
32
Q

The primary form of hyperparathyroidism is caused by what?

A

caused by benign tumor or hyperplasia of one or both parathyroid glands

33
Q

What are clinical signs of primary hyperparathyroidism?

A
  • increased PTH
  • hypercalcemia
  • hypophosphatemia
  • renal calculi
  • bone pain and fractures
34
Q

The secondary form of hyperparathyroidism is caused by what?

A

caused by increased phosphate in blood, which precipitates Ca and results in hypocalcemia which then causes secondary increase in PTH

35
Q

Secondary hyperparathyroidism may result from what?

A

renal failure or increased dietary phosphate

36
Q

Hypoparathyroidism may be caused by what?

A
  • accidental surgical removal
  • autoimmune destruction
  • idiopathic
37
Q

Hypoparathyroidism results in what?

A
  • decreased PTH
  • hypocalcemia
  • hyperphosphatemia
38
Q

How does calcitonin decrease blood Ca and P?

A
  • inhibiting bone resorption
  • increasing urinary P excretion
  • inihbiting renal reabsorption of Ca
39
Q

What are stimulators of calcitonin?

A
  • increased blood Ca
  • vitamin D (via feedback)
  • ingested food
40
Q

What sustance is required for bone formation and increases Ca absorption from GIT?

A

vitamin D

41
Q

Where is vitamin D synthesized and what form is it synthesized as?

A

synthesized in skin as precursor 7-dehydrocholesterol

42
Q

After synthesis or absorption in the gut, what happens to vitamin D in the liver?

A
  • converted to 25-hydroxyvitamin D
  • goes to kidney – most converted to 1,25-hihydroxyvitamin D
43
Q

Intermediates and active vitamin D are bound to what?

A

protein carriers

44
Q

What are the actions of vitamin D?

A
  • stimulates Ca absorption via calbindin in intestine
  • stimulates absorption of phosphate and Mg in intestine
  • weakly stimulates Ca and P reabsorption in kidney
  • stimulates bone resorption in presence of PTH
  • increases Ca transport and uptake by SR in skeletal muscle cells
  • decreases PTH synthesis
45
Q

When Ca intake is low, Ca absorption is an ____ process.

A

active

46
Q

When Ca intake is high, Ca absorption is a ______ process.

A

passive

Physiology (18 decks)

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