Calcium regulation

Question 1

What are hydroxyapatite crystals?

Answer 1

Calcium, Phosphate and Water- found within bone

Question 2

What is intracellular calcium?

Answer 2

Calcium that is bound to proteins/ within the mitochondria

Question 3

Why is it important to have calcium in extracellular fluid?

Answer 3

It helps control the calcium levels in the blood

Question 4

What are the three forms of calcium in the blood?

Answer 4

Bound to proteins, complexed to anions or freely ionised

Question 5

What controls the excretion of calcium?

Answer 5

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

Question 6

What are the two types of calcium store in bone?

Answer 6

readily exchangeable and slowly exchangeable

Question 7

Where is the readily exchangeable source of calcium located?

Answer 7

In the caniculli between osteocytes

Question 8

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

Answer 8

PTH stimulated pumps in the osteocytes which require ATP

Question 9

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

Answer 9

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

Question 10

What provides a ready source of phosphate for cells?

Answer 10

inorganic phosphate in the blood

Question 11

What is phosphate important for?

Answer 11

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

Question 12

What is the effect of PTH on phosphate?

Answer 12

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

Question 13

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

Answer 13

around 80-90%

Question 14

What are 4 calcium regulating hormones?

Answer 14

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

Question 15

What is the parathyroid gland?

Answer 15

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

Question 16

What do the darker staining cells in the parathyroid secrete?

Answer 16

PTH

Question 17

How is PTH secreted?

Answer 17

it is secreted by exocytosis

Question 18

What does PTH do?

Answer 18

It acts to increase the ECF concentration of calcium

Question 19

What detects the ECF calcium concentration

Answer 19

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

Question 20

What is calcidiol?

Answer 20

The inactive stored form of vitamin D

Question 21

What must be added for vitamin D to be activated?

Answer 21

OH groups

Question 22

What is PTHrP important for?

Answer 22

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

Question 23

Where is calcitonin produced?

Answer 23

By the chief cells in the parathyroid

Question 24

Where is the majority of calcium in the body found?

Answer 24

99% of it is in bone

Question 25

Where is calcium reabsorbed?

Answer 25

In the GI tract mostly

Question 26

Where is calcium excreted?

Answer 26

Mostly in the kidneys

Question 27

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

Answer 27

the PCT

Question 27

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

Answer 27

the PCT

Question 28

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

Answer 28

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

Question 29

What is the effect of PTH on phosphate concentrations

Answer 29

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

Question 30

What do increased levels of PTH do to the kidney? | in terms of calcium

Answer 30

Increased reabsorption of calcium into the blood

Question 31

What do increased levels of PTH do to the bone? | In terms of calcium

Answer 31

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

Question 32

What happens to vitamin D in the liver?

Answer 32

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

Question 33

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

Answer 33

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

Question 34

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

Answer 34

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

Question 35

How does calcitriol increase calcium uptake in the small intestine?

Answer 35

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

Question 36

What are some of the roles of PTHrP?

Answer 36

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

Question 37

What is Hypercalcaemia paraneoplastic syndrome?

Answer 37

Increased plasma calcium levels, leads to hypercalcaemia

Question 38

What is the main function of calcitonin?

Answer 38

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

Question 39

What hormones increase calcitonin secretion?

Answer 39

CCK, secretin and gastrin

Question 40

What organ does calcitonin work on?

Answer 40

The kidney

Question 40

What organ does calcitonin work on?

Answer 40

The kidney

Question 41

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

Answer 41

In the shell gland

Question 42

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

Answer 42

Inappatence, Ataxia, Paresis, Tetany