Calcium

Question 1

What are the functions of calcium

Answer 1

• bone and tooth structure
• mineral store
• action potentials (cardiac muscle)
• membrane excitability
• 2nd messenger
• co-factor in metabolic pathways
• blood clotting

Question 2

Give examples of how calcium acts as a second messenger

Answer 2

• muscle excitation-contraction coupling
• gland secretion
• non-steroid hormone action

Question 3

Describe parathyroid secretion

Answer 3

Secreted from parathyroid glands in response to low plasma (Ca2+)

Question 4

Acts to increase plasma calcium by:

Answer 4

• increase bone (osteoclasts)
• increase calcium response in kidney (with decreased oxygen reabsorption)
• increased uptake of Ca 2+ from the intestines

Question 5

When is parathyroid hormone secreted

Answer 5

Secreted from parathyroid glands in response to low plasma Ca2+

Question 6

How does calcitonin act to lower plasma calcium

Answer 6

Increased formation of bone (osteoblasts)
Decreased calcium resorption in kidney

Question 7

Describe diffusible calcium concentration

Answer 7

Ionised calcium 1.2mmol/l
Bound to citrate 0.2mmol/l

Question 8

What is the calcium concentration of non diffusible calcium

Answer 8

1.2mmol/l

Question 9

What is the calcium concentration of blood plasma

Answer 9

2.6mmol/l

Question 10

Name some functions of calcium

Answer 10

• bone and tooth structure
• mineral store
• action potentials (cardiac muscles)
• membrane excitability

Question 11

What is the role of calcium in muscles

Answer 11

Responsible for excitation contraction coupling

Question 12

What are some ways calcium can be obtained in the body

Answer 12

• diet
• kidneys
• exchangeable bone

Question 13

What hormones control calcium homestasis

Answer 13

• parathyroid hormone
• calcitonin
• vitamin D

Question 14

What is the role of parathyroid hormone in calcium secretion

Answer 14

• secreted from parathyroid glands in response to low plasma (Ca2+)
• acts to increase plasma calcium by - increasing osteoclastogenesis, increasing calcium Reabsorption by kidney and increasing uptake of calcium from the intestines (assisted by vitamin D)

Question 15

What is the role of calcitonin

Answer 15

• secreted from the thyroid glands in response to high plasma (Ca2+)
• acts to lower plasma calcium by increased osteoblastogenesis, decreased calcium resabsorption by the kidneys

Does not seem to play a massive role, no pathological effects

Question 16

What ways can vitamin D3 be obtained

Answer 16

• diet
• 7-dehydrocholestrol synthesised in the skin

Question 17

What is cholecalciferol

Answer 17

Vitamin D3 essential for the deposition of calcium in the bones and formed by the action of sunlight on the de hydro Cholestrol in the skin

Question 18

What happens to cholecalciferol in the kidney

Answer 18

Cholecalciferol converted into calcitrol in the kidney, this is regulated by PTH

Question 19

What effect does calcitrol have on the intestine

Answer 19

Increased calcium absorption

Question 20

What effect does calcitrol have on the kidney

Answer 20

Ca retention and PO4 retention of the kidney

Question 21

What effect does calcitrol have on bone

Answer 21

Ca release and PO4 release

Question 22

What overall effect does calcitrol have on the body

Answer 22

Increased levels of calcium and phosphate in the plama

Question 23

Name some hormones that increase bone formation and bone mass

Answer 23

• calcitonin
• growth hormone
• insulin
• IGF-1
• Oestrogen
• Testosterone

Question 24

Name some hormones that increase bone reabsorption and decrease bone mass

Answer 24

• cortisol
• parathyroid hormone
• thyroid hormones

Question 25

Where do osteoclasts lie in the bone

Answer 25

Lie in depressions known as howships lacunae

Question 26

What is hypercalcaemia

Answer 26

Raised calcium levels

Question 27

What is hypocalcemia

Answer 27

Reduced calcium levels

Question 28

What is hypocalcemia caused by

Answer 28

- decreased calcium intake - excessive calcium loss - alkalosis (low Ca2+) A panic attack could cause this, excessive blowing off of CO2, rebreathing air from a bag can solve this

Question 29

What are the effects of low calcium concentration

Answer 29

Increased nerve excitabity - pins and needles, muscle spasms - trousseaus sign, chvosteks sign

Question 30

What can hyperparathyrodism cause

Answer 30

Osteitis fibrosa - areas of demineralisation in the skull and legs

Question 31

What can hyperparathyroidism cause in the teeth

Answer 31

Defective mineralisation of teeth due to low blood calcium levels due to undersecretion of PTH

Question 32

What can vitamin D deficiency cause

Answer 32

Rickets (children) Osteomalacia (adults)

Question 33

What is osteoporosis

Answer 33

Decreased bone mass and density, fractures are common, more common in elderly

Question 34

What is osteopetrosis

Answer 34

Increased bone mass and density Results in - Reduced blood supply, fracture, chronic inflammation

Question 35

What can osteopetrosis cause in terms of dentistry

Answer 35

Difficult tooth extraction

Question 36

What is the term used to describe low calcium levels in the body

Answer 36

Alkalosis