Physiology of Bone and Calcium Homeostasis

Question 1

How is soft tissue growth measured?

Answer 1

Weight

Question 2

How is bone growth measured?

Answer 2

Height

Question 3

What are growth hormone and insulin-like growth factors needed for in tissue and bone growth?

Answer 3

Protein and cell division

Question 4

What is thyroid hormone’s role in growth?

Answer 4

Permissive role

Directly contributes to nervous system development

Question 5

What is the role of insulin in growth?

Answer 5

Supports growth

Provides glucose energy

Question 6

Of what adequate dietary requirements needed for bone growth?

Answer 6

Calcium

Protein

Question 7

What happens to long bones as they grow in length?

Answer 7

Bone diameter increases as matrix deposits on outer surface

Epiphyseal plate site of linear growth of long bones

Question 8

When is the epiphyseal plate active?

Answer 8

Childhood and adolescence

Question 9

Between what does hormonal control exchange calcium?

Answer 9

ECF and bone, kidneys, and intestine

Question 10

What is calcium important in?

Answer 10

Intracellular signalling
Structural
- Physical strength to bone matrix
- Helps hold cells together at tight junctions
Cofactor in blood coagulation
Normal excitability of neurons and muscle

Question 11

What are the three pools of calcium, and what proportion of total body calcium do they store?

Answer 11

Bone matrix = 99%
Extracellular fluid = 0.1%
Intracellular fluid = 0.9%

Question 12

Which pool of calcium can move to other locations?

Answer 12

That in extracellular fluid

Question 13

How much calcium is absorbed from the small intestine?

Answer 13

1/3

Question 14

What regulates calcium absorption?

Answer 14

Hormones

Question 15

How is calcium excreted?

Answer 15

Most through urine

Some through faeces

Question 16

Where in the nephron is calcium reabsorbed?

Answer 16

Distal tubule

Question 17

What regulates calcium excretion?

Answer 17

Hormones

Question 18

What secretes parathyroid hormone?

Answer 18

Parathyroid glands

Question 19

Is parathyroid hormone essential for life?

Answer 19

Yes

Question 20

In response to what is parathyroid hormone secreted?

Answer 20

Decreased plasma calcium

Question 21

What effect does parathyroid hormone have on the plasma?

Answer 21

Increases calcium

Decreases phosphate

Question 22

What are parathyroid hormone’s actions on bone?

Answer 22

Increases calcium and phosphate release from bone into plasma
Favours bone resorption via indirect action on osteoclasts

Question 23

What are parathyroid hormone’s actions on the distal nephron?

Answer 23

Increases calcium reabsorptuon

Decreases phosphate reabsorption

Question 24

What are parathyroid hormone’s actions on the intestine?

Answer 24

Indirectly increases calcium and phosphate reabsorption by activating vitamin D

Question 25

What is the chemical nature of parathyroid hormone?

Answer 25

Peptide

Question 26

What is the half-life of parathyroid hormone?

Answer 26

Less than 20 min

Question 27

What is the onset of action of parathyroid hormone?

Answer 27

2-3 hours for bone - Increased osteoclast activity in 1-2 hours 1-2 days for intestinal absorption Minutes for kidney transport

Question 28

What produces calcitonin?

Answer 28

C cells of thyroid gland

Question 29

When is calcitonin released?

Answer 29

Plasma calcium is high

Question 30

What does calcitonin do?

Answer 30

Decreases plasma calcium and phosphate

Question 31

What effect does calcitonin have on bone?

Answer 31

Decreases release of calcium from bone | Decreases bone resorption

Question 32

What effect does calcitonin have on the kidneys?

Answer 32

Increases calcium excretion

Question 33

When is calcitonin physiologically useful?

Answer 33

No role normally | Only works with extreme hypercalcaemia

Question 34

What is the effect of calcitonin on the gut?

Answer 34

None

Question 35

What is the chemical nature of calcitriol?

Answer 35

Steroid

Question 36

How is calcitriol transported in circulation?

Answer 36

Bound to plasma proteins

Question 37

What is the stimulus for synthesis of calcitriol?

Answer 37

Decreased calcium Indirectly via parathyroid hormone Prolactin

Question 38

Where is the target receptor for calcitriol?

Answer 38

Nuclear

Question 39

What are the roles of phosphate?

Answer 39

``` Energy transfer and storage - ATP - cAMP Control of - Enzymes - Transporters - Ion channels Part of DNA and RNA backbone ```

Question 40

What can cause hyperparathyroidism?

Answer 40

Tumour

Question 41

What can cause hypoparathyroidism?

Answer 41

Rare Autoimmune attack of glands Inadvertent parathyroidectomy during thyroid surgery

Question 42

What happens to calcium and phosphate levels in hyperparathyroidism?

Answer 42

Hypercalcaemia | Hypophosphataemia

Question 43

What happens to calcium and phosphate levels in hypoparathyroidism?

Answer 43

Hypocalcaemia | Hyperphosphataemia

Question 44

What can a vitamin D deficiency cause?

Answer 44

Impaired intestinal calcium absorption Parathyroid hormone maintains calcium levels at expense of bones Bone demineralisation

Question 45

What is bone demineralisation due to a vitamin D deficiency in children called?

Answer 45

Rickets

Question 46

What is bone demineralisation due to a vitamin D deficiency in adults called?

Answer 46

Osteomalacia

Question 47

What are the preventable risk factors for osteoporosis?

Answer 47

Low dietary calcium Lack of exercise Smoking