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
  Muscle: excitation-contraction coupling
  Gland secretion
  Non-steroid hormone action
• Co-factor in metabolic pathways
• Blood clotting

Question 2

what are the components involved in calcium homeostasis?

Answer 2

• parathyroid hormone
• calcitonin
• vitamin D

Question 3

where is the parathyroid hormone secreted from?

Answer 3

parathyroid glands

Question 4

what is the action which triggers the secretion of the parathyroid hormone?

Answer 4

low plasma Ca2+

Question 5

what does the parathyroid to in response to low plasma Ca2+?

Answer 5

• increases reabsorption of bone (osteoclasts)
• increases calcium ion reabsorption in kidney
• increases uptake of calcium ions from the intestines (assisted by vit D)

Question 6

what is a very important element in calcium turnover?

Answer 6

exchangeable bone

Question 7

what is meant by exchangeable bone?

Question 8

where is calcitonin secreted from?

Answer 8

the thyroid glands

Question 9

what triggers the release of calcitonin by the thyroid glands?

Answer 9

high plasma Ca2+

Question 10

how does calcitonin act in response to an increase in plasma Ca2+?

Answer 10

• increases formation of bone (osteoblasts)
• decreased calcium ion reabsorption in the kidney

Question 11

vitamin D

Question 12

which hormones increase both bone formation and bone mass?

Answer 12

• calcitonin
• growth hormone
• IGF-1
• insulin
• oestrogen
• testosterone

Question 13

which hormones increase bone resorption and decrease bone mass?

Answer 13

• cortisol
• parathyroid hormone
• thyroid hormones

Question 14

bone remodelling

Question 15

what is hypercalcaemia?

Answer 15

raised Ca2+

Question 16

what is hypocalcaemia?

Answer 16

reduced Ca2+

Question 17

what is hypocalcaemic tetany?

Answer 17

a condition surrounding decreased Ca2+ due to:
- decreased intake
- excessive loss
- alkalosis (low Ca2+)
leads to increased nerve excitability:
- pins and needles
- muscles spasms
- trousseaus sign
- chvosteks sign

Question 18

what is hyperventilation an example of?

Answer 18

hypocalcaemia
- panic attack can cause alkalosis by blowing off CO2
- treated by rebreathing expired air from bag

Question 19

what is osteitis fibrosa cystica?

Answer 19

• results from hyperparathyroidism
• areas of demineralisation in skull and leg bones

Question 20

what can result from hypoparathyroidism?

Answer 20

• defective mineralisation of teeth

Question 21

what are the consequences of a vitamin D deficiency?

Answer 21

• decreased Ca uptake from GI tract
• unmineralised bone
• bone lacks rigidity
• rickets/osteomalacia

Question 22

what is a condition in children associated with a vit D deficiency?

Answer 22

rickets

Question 23

what is a condition in adults associated with a vit D deficiency?

Answer 23

osteomalacia

Question 24

what are the effects of varying levels of calcitonin?

Answer 24

no obvious clinical consequences

Question 25

what is osteoporosis?

Answer 25

decreased bone mass and density - fractures common - common in elderly - more common in women

Question 26

what is osteopetrosis?

Answer 26

increased bone mass and density - reduced blood supply - prone to fracture - prone to chronic infection - difficult extractions