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VMS 1008 > Calcium regulation > Flashcards

Calcium regulation Flashcards

1
Q

What are hydroxyapatite crystals?

A

Calcium, Phosphate and Water- found within bone

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2
Q

What is intracellular calcium?

A

Calcium that is bound to proteins/ within the mitochondria

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3
Q

Why is it important to have calcium in extracellular fluid?

A

It helps control the calcium levels in the blood

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4
Q

What are the three forms of calcium in the blood?

A

Bound to proteins, complexed to anions or freely ionised

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5
Q

What controls the excretion of calcium?

A

The glomerulus, around 99% of the calcium is then reabsorbed

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6
Q

What are the two types of calcium store in bone?

A

readily exchangeable and slowly exchangeable

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7
Q

Where is the readily exchangeable source of calcium located?

A

In the caniculli between osteocytes

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8
Q

How is calcium moved from the bone fluid to the plasma in rapid exchange?

A

PTH stimulated pumps in the osteocytes which require ATP

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9
Q

How is calcium moved from bone fluid to plasma in slow exchange?

A

Transported via a PTH independent process, but osteoclasts break down the bone

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10
Q

What provides a ready source of phosphate for cells?

A

inorganic phosphate in the blood

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11
Q

What is phosphate important for?

A

Structure of bones/Teeth, cell membranes, DNA synthesis and ATP

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12
Q

What is the effect of PTH on phosphate?

A

PTH decreases the number of transporters in the nephron- therefore decreasing reabsorption and increasing excretion

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13
Q

What is the percentage of phosphate that the renal tubules reabsorb into the blood?

A

around 80-90%

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14
Q

What are 4 calcium regulating hormones?

A

Parathyroid hormone, Vitamin D, Parathyroid hormone related peptide, and calcitonin

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15
Q

What is the parathyroid gland?

A

4 small nodules that are associated with the thyroid gland that controls central calcium and phosphate metabolism

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16
Q

What do the darker staining cells in the parathyroid secrete?

A

PTH

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17
Q

How is PTH secreted?

A

it is secreted by exocytosis

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18
Q

What does PTH do?

A

It acts to increase the ECF concentration of calcium

19
Q

What detects the ECF calcium concentration

A

It is detected by calcium-sensitive receptors on chief cell membranes

20
Q

What is calcidiol?

A

The inactive stored form of vitamin D

21
Q

What must be added for vitamin D to be activated?

A

OH groups

22
Q

What is PTHrP important for?

A

Important for regulation of placental transport of calcium to foetus and transfer of calcium from blood to milk

23
Q

Where is calcitonin produced?

A

By the chief cells in the parathyroid

24
Q

Where is the majority of calcium in the body found?

A

99% of it is in bone

25
Q

Where is calcium reabsorbed?

A

In the GI tract mostly

26
Q

Where is calcium excreted?

A

Mostly in the kidneys

27
Q

What part of the kidney does the most calcium excretion/reabsorption

A

the PCT

27
Q

What part of the kidney does the most calcium excretion/reabsorption

A

the PCT

28
Q

Why is it important that calcium is bound to a protein when entering a cell?

A

Calcium has a lot of effects in the cell, so if it is free floating in the cell there will be effects that we do not want

29
Q

What is the effect of PTH on phosphate concentrations

A

It decreases renal absorption of phosphate, therefore increasing excretion of phosphate

30
Q

What do increased levels of PTH do to the kidney?

in terms of calcium

A

Increased reabsorption of calcium into the blood

31
Q

What do increased levels of PTH do to the bone?

In terms of calcium

A

Increased mobilisation of calcium from the bone/ increased calcium pumping to ECF

32
Q

What happens to vitamin D in the liver?

A

an OH group is added to form calcidiol which is an inactive form, this can then be stored in adipose tissue

33
Q

What happens to calcidiol in the kidney if the levels of calcium are normal

A

24-hydroxylase adds 2nd OH group to form an inactive form which is then excreted by the kidney

34
Q

What happens to calcidiol in the kidney if the levels of calcium are low?

A

PTH stimulates 1α-hydroxylase to add a second OH group in a different place
this forms the active version (calcitriol) which increases absorption of calcium in the GI tract

35
Q

How does calcitriol increase calcium uptake in the small intestine?

A

Increases Ca2+ channels in the apical side
increases Ca2+ pumps in the basolateral side
Increases transcellular absorption

36
Q

What are some of the roles of PTHrP?

A

proliferation, differentiation and apoptosis
placental transport of calcium to and from the foetus

37
Q

What is Hypercalcaemia paraneoplastic syndrome?

A

Increased plasma calcium levels, leads to hypercalcaemia

38
Q

What is the main function of calcitonin?

A

acts to reduce calcium and phosphate
decreased movement of calcium from bone pools to teh ECF
inhibits osteoclastic activity
increases renal excretion

39
Q

What hormones increase calcitonin secretion?

A

CCK, secretin and gastrin

40
Q

What organ does calcitonin work on?

A

The kidney

40
Q

What organ does calcitonin work on?

A

The kidney

41
Q

Where is the calcium carbonate required for the production of egg shells produced?

A

In the shell gland

42
Q

What can occur if loss of calcium from the ECF exceeds the calcium available in the bone pools?

A

Inappatence, Ataxia, Paresis, Tetany

VMS 1008 (20 decks)

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