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Flashcards in Bone and Calcium Deck (35):
1

Where is calcium in the blood?

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

2

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

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

3

What can alkalosis do to calcium?

Hypocalcaemia as blowing off lots of CO2
lips tingle

4

What is the role of calcium?

Circulating molecules INSIDE cells
stabilises sodium pumps sitting wihin channels to prevent activity

5

What happens during hypocalcaemia?

Uncontrolled nerve firing = cardiac arrhythmias/cardiac arrest

6

Where is the location of phosphate?

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

7

How much calcium is in bone?

99%

8

What is the role of the parathyroid glands?

Secrete parathyroid hormone when low calcium via chief cells
Cause increase in extracellular calcium

9

How do the parathyroid increase EC calcium?

- 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

10

How does phosphate change calcium concentrations?

Forms salts with calcium so decreases ionised mounts

11

What do high levels of calcium do to PTH?

- inhibit PTH
- not fully suppressed (basal amount secreted)
- slight secretion decrease not major

12

What do low levels of calcium do to PTH?

- lack of calcium picked up by calcium sensing receptor
- dramatic increase in PTH secretion

13

What is the role of the calcium sensing receptor?

- reduces PTH secretion
- increases PTH breakdown
- suppresses PTH gene transcription

14

How does familial hypocalciruic hypercalcemia occur?

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

15

What other factors affect PTH secretion?

- increased by phsophate
- decreased by activated vitamin D

16

Where does PTH act on in the kidney?

D.C.T
upregulates channels

17

Where does calcium reabsorption take place?-

- DCT: PTH acts here
- PCT: paracellular, voltage gradient drives it
- LOH: paracellular, voltage gated driven, loop diuretics inhibit

18

What does calcium consist of in the bone?

hydroxyapatite

19

What is the bone made up of?

Collagen
Hydoxyapatite

20

What is bone made up of when it gets mineralised?

Calcium, phosphate, alkaline phospahtase

21

What do oesteoblasts do?

Contain and produce RANKL

PTH stimulate its production

22

What is RANKL

Stimulated by PTH

23

What do osteoclasts do?

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

24

How do you intake vitamin D?

Absorb by diet or UV light

25

What is vitamin D converted to and how?

Hepatic conversion
- 125-hydoxyvitamin D

26

properties of the vitamin D receptor?

- nuclear and membrane bound
- negative feedback

27

What is the function of vitamin D

- increases calcium and phosphate absorption from the gut and kidney
- stimulates bone reabsorption and remodelling

28

What are the affects of vitamin D deficiency?

- rickets
- osteomalacia
- osteoporosis

29

What causes vitamin D deficiency?

poor diet
lack of sunlight

30

What is FGF23?

Secreted by osteoblasts in response to high phosphate
Decreases calcium and phosphate levels

31

What is calcitonin?

Made by thyroid C-cells
Marker of medullary thyroid cancer

32

What is PTHrP?

PTH-related peptide
- lactation role

33

What is hyperparathyroidism?

- increased PTH levels
= renal calculi (stones), osteoporosis, dyspepsia, depression/confusion, polyuria, polydipsia

34

What are the 3 types of hyperparathyroidism?

- 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

What is hypoparathyroidism?

- iatrogenic
-decreased PTH
- convulsions/arrhythmias/seizures/paraesthesia