Calcium Physiology

Question 1

what are the main functions of calcium

Answer 1

bone and tooth structure
mineral store
action potentials
membrane excitability
second messengers
co factor in metabolic pathways
blood clotting

Question 2

describe the second messenger action of calcium

Answer 2

acts in:
muscle for excitation contraction coupling
gland secretion
non steroid hormone action

Question 3

describe the concentration of ionised calcium

Answer 3

1.2mmol/litre

Question 4

what is the concentration of calcium bound to citrate

Answer 4

0.2mmol/litre

Question 5

what are the forms of diffusible calcium

Answer 5

ionised calcium and bound to citrate

Question 6

what are the forms of non diffisuble calcium

Answer 6

bound to protein

Question 7

what is the concentration of calcium bound to protein

Answer 7

1.2mmol/litre

Question 8

what is the total calcium concentration

Answer 8

2.6 mmol/litre

Question 9

which molecules are involved in calcium homeostasis

Answer 9

parathyroid hormone
calcitonin
vitamin D

Question 10

describe parathyroid hormone secretion

Answer 10

produced from the parathyroid gland in resopnse to low plasma calcium concentration

Question 11

how does parathyroid hormone increase plasma calcium

Answer 11

• increase resorption of bone through osteoclast activity
• increase calcium resorption in the kidneys with a decrease in phosphate resorption
• increased uptake of calcium from the intestines, with the assistance of vitamin D

Question 12

what happens in the kidneys to increase plasma calcium concentration

Answer 12

increased formation of calcitriol (active vitamin D)
increased calcium resorption
increased phosphate excretion

Question 13

what is 1.25 hydroxyvitamin D

Answer 13

this is the most active form of vitamin D known as calcitriol

Question 14

describe calcitonin secretion

Answer 14

produced from thyroid glands in resopnse to high plasma calcium concentration

Question 15

how does calcitonin act

Answer 15

lowers plasma calcium by increases the formation of bone through osteoblastogenesis and a decrease in calcium resorption in the kidney

Question 16

does calcitonin play a role in calcium homeostasis

Answer 16

not a major one

Question 17

what is the form of vitamin D formed in the skin from UV

Answer 17

7-dehydrocholesterol

Question 18

what is vitamin D3

Answer 18

cholecalciferol, formed from dietary vitamin D and 7-dehydrocholesterol

Question 19

describe vitamin D production

Answer 19

• diet and skin provide two forms
• 7-hydrocholesterol in the skin
• come together to form vitamin D3
• this goes to liver and is acted upon by 25-hydroxylase
• to form 25 hydroxy cholecalferol
• this is acted upon in the kidney by 1alpha hydrolyase
• this forms calcitriol

Question 20

describe the destination of calcitriol

Answer 20

intestines for calcium absorption
kidney for calcium retentin and phosphate retention
bone for calcium and phosphate release

Question 21

which hormones increase bone formation and bone mass

Answer 21

calcitonin
growth hormone
IGF
insulin
oestrogen
testosterone

Question 22

which hormones decrease bone mass through increasing bone resorption

Answer 22

cortisol
parathyroid homrone
thyroid hormones

Question 23

what do osteoblasts do

Answer 23

they synthesis and secrete collagen fibres forming a matrix later mineralised by calcium salts

Question 24

what are osteocytes

Answer 24

these are trapped osteoblasts in the bone matrix
they lie within bony lacunae and contact other cells via long cytoplasmic processes

Question 25

what are osteoclasts

Answer 25

large, multinucleated cells derived from macrophages, that resorb bone

Question 26

where do osteoclasts lie in bone

Answer 26

howships lacunae

Question 27

desribe hypocalcaemic tetany

Answer 27

this is a decrease in calcium concentration due to decreased intake, excessive loss, or alkalosis leads to low nerve excitability, causing muscle spasms, pinks and needles and trousseaus sign

Question 28

what is alkalosis

Answer 28

low calcium concentration

Question 29

what is hypocalcaemia

Answer 29

this is caused from hyperventilation, as in panic attacks which can cause alkalosis happens due to blowing off carbon dioxide

Question 30

what is osteitis fibrosa cystica

Answer 30

areas of demineralisation in the skull and leg bones

Question 31

what can hypoparathyroidism do to the teeth

Answer 31

lead to defective mineralisation of teeth due to low blood calcium levels due to undersecretion of parathyroid hormone

Question 32

what can cause vtiamin D deficiency

Answer 32

dietary deficiency, or a failure to synthesise in the body

Question 33

what does vitamin D deficiency do to the body

Answer 33

decreases calcium uptake from the gastrointestinal tract leads to undermineralised bone leads to unmineralised bone lacking rigidity

Question 34

what does vitamin D deficiency cause in children

Answer 34

rickets

Question 35

what does vitamin D deficiency cause in adults

Answer 35

osteomalacia

Question 36

what is osteoporosis

Answer 36

decreased bone mass and density

Question 37

what is osteopetrosis

Answer 37

increased bone mass and density

Question 38

describe osteoporosis in patients

Answer 38

reduced bone dentistry due to a loss of matric and mineral leads to fractures common in the elderly, particularly women

Question 39

what are the causes of osteoporosis

Answer 39

nutritional deficiency and corticosteroids

Question 40

describe osteopetrosis in patients

Answer 40

increased bone density leads to reduced blood supply bones are prone to fracture and chronic infection makes extractions difficult mandible is larger than maxilla