Calcium Homeostasis

Question 1

Where is the main reservoir of calcium

Answer 1

Skeleton
1200g

Question 2

Apart from the skeleton calcium can be stored in extra-cellular space why is this important

Answer 2

It is important for cells functions such as
Normal blood clotting
Muscle contractility
Nerve function

Question 3

What is the total serum calcium

Answer 3

Around 2.4 mol/L

Question 4

What is the total ionised serum calcium

Answer 4

Around 1.1 mol/L

Question 5

If calcium is ionised what does this mean

Answer 5

Metabolically active

Question 6

If calcium is protein bound what does this mean

Answer 6

It is not metabolically active

Question 7

What are examples of complexed calcium

Answer 7

Citrate
Phosphate

Question 8

When is albumin most likely going to bind to calcium

Answer 8

At higher pH

Question 9

What is low iconised calcium associated with

Answer 9

It is associated with contraction of the small muscles of the hands and feet

Question 10

Low ionised calcium can be an effect of what

Answer 10

Alkalosis

Question 11

How much calcium do we absorb from our diet

Answer 11

30%

Question 12

What is a major source of dietary calcium

Answer 12

Dairy products

Question 13

What are minor sources of dietary calcium

Answer 13

Veg such as broccoli
Cereals such as white bread
Oily fish such as sardines

Question 14

Where is active absorption of calcium happening

Answer 14

Active absorption occurs in the duodenum and jejunum

Question 15

Where is passive absorption seen

Answer 15

Passive absorption occurs in the ileum and colon

Question 16

When do we absorb a higher amount of calcium

Answer 16

When we are put on a low calcium diet

Question 17

What is calcium absorption mediated by

Answer 17

Calcritriol

Question 18

What is calcitriol

Answer 18

The active form of vitamin D

Question 19

How is calcium absorbed

Answer 19

Active transport

Question 20

Where is exchangeable calcium found

Answer 20

On the bone surface

Question 21

What happens during bone resorption

Answer 21

Calcium is released from bone slowly by osteoclasts

Question 22

What does the amount of calcium filtered by the glomerulus depend on

Answer 22

The glomerular filtration rate

Question 23

What is ultrafilterable calcium

Answer 23

Ionised and complexed

Question 24

How much of the calcium which is filtered is reabsorbed

Answer 24

98%

Question 25

Higher levels of calcium will be reabsorbed if what is high

Answer 25

Parathyroid hormone

Question 26

What causes less calcium to be reabsorbed

Answer 26

Sodium is high

Question 27

How many amino acids is parathyroid hormone

Answer 27

84 amino acids

Question 28

What can detect the levels of ionised calcium to stimulate PTH been secreted

Answer 28

Calcium sensing receptors on the parathyroid gland

Question 29

What regulates the synthesis of PTH

Answer 29

Calcitriol

Question 30

Where does regulation of PTH take place

Answer 30

Parathyroid chief cell

Question 31

What does calcitriol stimulate

Answer 31

It stimulates intestinal calcium absorption

Question 32

Where is calcitonin produced

Answer 32

It is produced by c cells or parafollicular cells of the thyroid

Question 33

When is calcitonin released

Answer 33

It is secreted due to an increase in serum calcium

Question 34

What affect does it have on resorption

Answer 34

Lowers bone resorption

Question 35

What does parathyroid hormones act on

Answer 35

Bone and kidney

Question 36

What does parathyroid hormone have an effect on

Answer 36

In the kidneys- increased calcium reabsorption, decreased phosphate reabsorption and increases alpha-hydroxylation of 25-OH vit D In the bone- increased bone remodelling In the intestines- no direct effect but increase in calcium absorption due to increase in 1,25 vit D

Question 37

What are bodily responses to a low diet of calcium

Answer 37

Low dietary calcium means less calcium is absorbed which results in lower ionised serum calcium cause high amounts of PTH which results in fast action in exchangeable calcium released from the surface of done and decreased excretion of calcium from the kidney The slow actions = increased bone resorption and increase in fractional absorption by intestine To return serum ionised calcium back to normal

Question 38

What is calcium homeostasis

Answer 38

Example of negative feedback