Calcium Physiology

Question 1

What is the normal calcium concentration

Answer 1

2.4mmol/L

Question 2

Why is calcium so tightly controlled

Answer 2

It is critical for electrical impulses of the neuronal, muscular contractions

Question 3

Effect of hypercalcaemia on the nervous system

Answer 3

Depression

Question 4

Effect of Hypocalcaemia on the nervous system

Answer 4

Hyperexcitation

Question 5

Outline the distribution of calcium in the body

Answer 5

0.1% in the blood, 99% is in the bones and 1% in he ells

Question 6

Outline the 3 methods of carrying calcium

Answer 6

Protein bound (40%)
Anion bound (10%)
Free circulating ions (50%)

Question 7

What is calcium complexed with in the blood

Answer 7

Phosphorous ions

Question 8

What intracellular actions does calcium affect

Answer 8

Enzyme, cell division and exocytosis

Question 9

Describe th changes in the plasma membrane potentiation with hypocalcaemia

Answer 9

Increases the electrical gradient, which increases Na permeability –> spontaneous excitaiton

Question 10

Describe the changes in the plasma membrane potentiation with hypercalcaemia

Answer 10

Decreases membrane electrical gradient, reduces Na permeability, reduces electrical activity

Question 11

What proportion of Calcium from diet is absorbed

Answer 11

10%

Question 12

Describe the limitations of calcium absorption

Answer 12

Only 350mg of 1g are absorbed by the enterocytes, then 250mg of this remains in the cytoplasm and therefore is lost during sloughing

Question 13

What forms of calcium can be excreted?

Answer 13

Anion bound and serum free calcium

Question 14

Describe the composition of bone

Answer 14

Bone is organic matrix and calcium salts

Question 15

Describe the organic matrix in bone

Answer 15

Colalgen fibers and ground substance

Question 16

What is the role of collagen fibres in the organic matrix of bone?

Answer 16

For tensile strength

Question 17

What is the composition of ground substance in organic matrix of bone

Answer 17

Formed of proteoglycans and chondroitin sulphate + hyaluronic acid

Question 18

What is the constituents and use of hydroxyapatitie

Answer 18

Calcium and phosphate for compressional strength

Question 19

What prevents the formation of hydroxyapatite in the blood?

Answer 19

Pyrphosphate

Question 20

Illustrate the process of bone calcification

Answer 20

Osteoblasts secrete collagen molecules and ground substance to which calcium slats can bind

Question 21

Illustrate the changes in serum calcium following an injection

Answer 21

Within 30minutes it is restored, as bone calcium is highly exchangeable

Question 22

Effect of PTH on serum calcium and phosphate

Answer 22

Increases serum calcium, decreases serum phosphate

Question 23

Effect of calcitriol o serum calcium and phosphate

Answer 23

Increases both

Question 24

Effect of calcitonin on serum calcium andphosphate

Answer 24

Decreases both

Question 25

Effect of PTH on the goes gut and kidneys

Answer 25

Bones: osteoclast resorption kidneys: Calcium ion resorption and phosphate excretion

Question 26

Effect of calcitiol on the gut

Answer 26

Increases calcium and phosphate resorption

Question 27

Effect of calcitonin on the bone and kidneys

Answer 27

Inhibits osteoclast resorption and promotes calcium excretion from kidneys

Question 28

Structure of vitamin d

Answer 28

Fat-soluble steroid

Question 29

What is the overall effect of vitamin D

Answer 29

Increases total calcium, magnesium and phosphate

Question 30

How is vitamin D transported?

Answer 30

Bound to the Bit D binding protein

Question 31

What are the 2 major sites of vitamin D action?

Answer 31

Gut and bone, where it increases absorption

Question 32

What is the mechanism of action of vitamin D on the Kidneys

Answer 32

Increases Calcium and phosphate absorption by the epithelial cells

Question 33

How does Vitamin D promote bone absorption of calcium

Answer 33

Potentiates the effects of PTH to increase bone absorption

Question 34

How does Vitamin D promote intestinal calcium absorption

Answer 34

1,25-Dihydroxycholecalciferol acts as a hormone to increase Ca-binding protein in the intestinal epithelium

Question 35

What stimulates PTH release

Answer 35

Low serum Calcium and high serum PO4

Question 36

What inhibits PTH release

Answer 36

Low serum Mg, high serum Ca

Question 37

What stimulates Calcitriol rlease

Answer 37

Low serum PO4 or PTH

Question 38

what is the rate limiting step and therefore the modulator of calcitriol production

Answer 38

Calcitriol production in the kidneys

Question 39

What are th major sites of PTH action?

Answer 39

Osteoclasts (resorption), Intestines (Absorption), Kidneys (increase Vitamin production and renal tubular reabsorption and excrete phosphate)

Question 40

Describe the Ca sensing receptor

Answer 40

Case is a GPCR on the PTH chief cells, thyroidal cC cells and Loop of Henle

Question 41

When can CaSR be mutated

Answer 41

Familial Benign Hypocaciuric Hypercaclaemia | Neonatal severe hyperparathyroidism

Question 42

How do mutations in the CaSR lead to high calcium

Answer 42

Parathyroid gland: can stop secreting PTH | Kidneys; can't stop reabsorbing the calcium

Question 43

What is the plasma membrane calcium gradient

Answer 43

Difference of 10^7 (ECF = 10^7 higher concentration than ICF)