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Metabolism > Calcium > Flashcards

Calcium Flashcards

1
Q

What are the main functions of calcium?

A

builds and maintains bones and teeth
helps regulate passage of nutrients
assists in normal blood clotting
helps maintain proper nerve and muscle function
needed for intracellular signalling pathways
appropriate levels needed for nerve transmission

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2
Q

How is calcium stored in bone?

A

Hydroxyapatite crystals

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3
Q

Why don’t we want high levels of calcium and phosphate in the blood?

A

Crystals may form in the blood

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4
Q

What are the effects of PTH?

A

stimulates bone resorption and release of calcium
stimulates calcium reabsorption in kidney
increased excretion of phosphate
activates vitamin D by hydroxylation

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5
Q

What are the effects of dietary vitamin D?

A

increases intestinal absorption of calcium
increases renal reabsorption of calcium
increases bone resorption

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6
Q

What does calcitonin do?

A

Counteracts the effects of PTH to decrease serum calcium levels

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7
Q

Where is calcitonin released?

A

C cells in the thyroid gland

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8
Q

How many parathyroid glands are there?

A

4

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9
Q

Which cells secrete PTH?

A

Chief cells of the parathyroid gland

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10
Q

What type of hormone is PTH?

A

Peptide

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11
Q

How does low serum calcium affect the chief cells?

A

up-regulation of transcription of PTH

prolonged survival of PTH mRNA

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12
Q

Where is PTH degraded?

A

released PTH is degraded in the liver

non-released PTH is degraded in the chief cells

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13
Q

What kind of receptor is the calcium receptor on the chief cells?

A

G protein

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14
Q

How does increased serum calcium reduce PTH release?

A

binds to receptors
inhibits adenylate cyclase
reduced cAMP
reduced PTH release

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15
Q

When PTH release is decreased, is it due to increased degradation or decreased synthesis?

A

Increased degradation

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16
Q

How would high phosphate levels affect PTH secretion?

A

Increased PTH secretion

17
Q

High would high magnesium levels affect PTH secretion?

A

decreased PTH secretion

18
Q

How do osteoblasts work?

A

They produce collagen matrix which is mineralised by hydroxyapatite.

19
Q

How do osteoclasts work?

A

They produce an acidic micro-environment which dissolves hydroxyapatite.

20
Q

How does PTH increase bone resorption?

A

cytokines released
stimulates osteoclasts activity and reduces osteoblast activity
resorption of mineralised bone occurs

21
Q

Where is calcium reabsorbed in the kidneys?

A

ascending limb

DCT

22
Q

Where is the greatest uptake of calcium?

A

Duodenum and jejunum

23
Q

Does the uptake of calcium require energy?

A

Yes

24
Q

How is vitamin D made in the skin?

A

through the action of sunlight on cholesterol

25
Q

What are the 2 forms of vitamin D and where do they come from?

A

D3 - made in skin and from dairy

D2 - from yeast and fungi

26
Q

Which form of vitamin D is added to margarines?

A

D2

27
Q

What does vitamin D form when activated?

A

calcitriol

28
Q

How many hydroxylation reactions does it take to activate vitamin D and where do they occur?

A

2 hydroxylation reactions
first reaction = liver
second reaction = kidney

29
Q

What is the half-life of calcitriol?

A

1/4 day

30
Q

Which enzyme is required for hydroxylation of vitamin D?

A

1 alpha-hydroxylase

31
Q

How does calcitriol work to increase calcium uptake in the gut?

A

Increases the sensitivity of microvilli calcium channels in the gut

32
Q

What are the signs of hypocalcaemia?

A

pins and needles
paralysis
tetany (spasms)
convulsions

33
Q

What are the signs of chronic hypercalcaemia?

A 
renal stones
kidney damage
constipation
dehydration
tiredness
depression
34
Q

What is the treatment for hypercalcaemia?

A

fluids

check for tumour causing over-secretion of PTH

35
Q

Where would PTH related peptide be released from?

A

Tumours in other places around the body

36
Q

What would primary hyperparathyroidism be caused by?

A

A parathyroid adenoma

37
Q

What is rickets?

A

a disease in children

long bone has failed to mineralise due to calcium/vitamin D deficiency

38
Q

How does vitamin D regulate phosphate levels?

A

Stimulates the uptake of phosphate in the gut

39
Q

How can calcium travel in theblood?

A

free calcium
bound to plasma proteins
complexed with citrate

Metabolism (17 decks)

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