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MET2 > Bone and Calcium > Flashcards

Bone and Calcium Flashcards

1
Q

Where is calcium in the blood?

A

50% albumin bound
40% ionised
10% complex bound with phosphate/citrate

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2
Q

What is the difference in calcium location during an acid state compared to an alkalotic state?

A

Acidotic - less albumin bound calcium as replaced by H+ and more ionised
Alkalotic: more albumin bound and less ionised

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3
Q

What can alkalosis do to calcium?

A

Hypocalcaemia as blowing off lots of CO2

lips tingle

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4
Q

What is the role of calcium?

A

Circulating molecules INSIDE cells

stabilises sodium pumps sitting wihin channels to prevent activity

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5
Q

What happens during hypocalcaemia?

A

Uncontrolled nerve firing = cardiac arrhythmias/cardiac arrest

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6
Q

Where is the location of phosphate?

A

85% mineralised in bone
Serum phosphate
In structural/informational/effector molecules

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7
Q

How much calcium is in bone?

A

99%

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8
Q

What is the role of the parathyroid glands?

A

Secrete parathyroid hormone when low calcium via chief cells

Cause increase in extracellular calcium

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9
Q

How do the parathyroid increase EC calcium?

A
  • bone: increase osteoclast activity = bone reabsorption = less calcium and phosphate release
  • kidney: increases calcium reabsorption, decreases phosphate reabsorption
  • intestines: increased hydroxylation of vitamin D. to produce calcitriol which promotes calcium reabsorption through gut by stimulating calcium binding proteins
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10
Q

How does phosphate change calcium concentrations?

A

Forms salts with calcium so decreases ionised mounts

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11
Q

What do high levels of calcium do to PTH?

A
  • inhibit PTH
  • not fully suppressed (basal amount secreted)
  • slight secretion decrease not major
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12
Q

What do low levels of calcium do to PTH?

A
  • lack of calcium picked up by calcium sensing receptor

- dramatic increase in PTH secretion

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13
Q

What is the role of the calcium sensing receptor?

A
  • reduces PTH secretion
  • increases PTH breakdown
  • suppresses PTH gene transcription
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14
Q

How does familial hypocalciruic hypercalcemia occur?

A
  • inactivate calcium sensing receptors o PT cannot sense if high and PTH not suppressed
  • high serum calcium means more reabsorbed and less in urine
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15
Q

What other factors affect PTH secretion?

A
  • increased by phsophate

- decreased by activated vitamin D

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16
Q

Where does PTH act on in the kidney?

A

D.C.T

upregulates channels

17
Q

Where does calcium reabsorption take place?-

A
  • DCT: PTH acts here
  • PCT: paracellular, voltage gradient drives it
  • LOH: paracellular, voltage gated driven, loop diuretics inhibit
18
Q

What does calcium consist of in the bone?

A

hydroxyapatite

19
Q

What is the bone made up of?

A

Collagen

Hydoxyapatite

20
Q

What is bone made up of when it gets mineralised?

A

Calcium, phosphate, alkaline phospahtase

21
Q

What do oesteoblasts do?

A

Contain and produce RANKL

PTH stimulate its production

22
Q

What is RANKL

A

Stimulated by PTH

23
Q

What do osteoclasts do?

A

RANKL receptors

- when activated form seal over bone and cause breakdown of RANKL releasing calcium

24
Q

How do you intake vitamin D?

A

Absorb by diet or UV light

25
Q

What is vitamin D converted to and how?

A

Hepatic conversion

- 125-hydoxyvitamin D

26
Q

properties of the vitamin D receptor?

A
  • nuclear and membrane bound

- negative feedback

27
Q

What is the function of vitamin D

A
  • increases calcium and phosphate absorption from the gut and kidney
  • stimulates bone reabsorption and remodelling
28
Q

What are the affects of vitamin D deficiency?

A
  • rickets
  • osteomalacia
  • osteoporosis
29
Q

What causes vitamin D deficiency?

A

poor diet

lack of sunlight

30
Q

What is FGF23?

A

Secreted by osteoblasts in response to high phosphate

Decreases calcium and phosphate levels

31
Q

What is calcitonin?

A

Made by thyroid C-cells

Marker of medullary thyroid cancer

32
Q

What is PTHrP?

A

PTH-related peptide

- lactation role

33
Q

What is hyperparathyroidism?

A
  • increased PTH levels

= renal calculi (stones), osteoporosis, dyspepsia, depression/confusion, polyuria, polydipsia

34
Q

What are the 3 types of hyperparathyroidism?

A
  • primary disease: due to parathyroid adenoma, carcinoma hyperplasia = hypercalcemia
  • secondary: compensates for decreased calcium by increasing PTH
  • tertiary successful compensation for chronic secondary hyperparathyroidism
35
Q

What is hypoparathyroidism?

A
  • iatrogenic
  • decreased PTH
  • convulsions/arrhythmias/seizures/paraesthesia

MET2 (26 decks)

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