calcium homeostasis

Question 1

how much calcium is ionised in the body

Answer 1

60%

Question 2

how much calcium in body

Answer 2

1kg

99 % in bone

Question 3

how much calcium intracellular

Answer 3

100nM basal

Question 4

what is calcium involved in

Answer 4

intracellular signalling

Question 5

where is calcium stored in cells

Answer 5

ER or ribosomes

Question 6

calcium in response to electrical signal

Answer 6

in muscles

calcium’s released from the sarcoplasmic reticulum to lead to muscle contraction via tin and myosin

Question 7

symptoms if calcium is not balanced

Answer 7

reduced blood flow
neuromuscular irritability
hypocalceamia causes Na influx
tetanic contraction

Question 8

recommended calcium intake

Answer 8

700mg per day

children more due to laying down of bone

Question 9

uptake oc calcium routes

Answer 9

transcellular

paracellular

Question 10

transcellular uptake

Answer 10

low intake
active transport
required binding of proteins, use of aTP to transport small amounts of Ca2+

Question 11

paracellular

Answer 11

high intake
passive
i.e. high intake from gut into cells

Question 12

homeostasis

Answer 12

• high calcium levels may lead to excretion via the kidney, most calcium is reabsorbed though
• bone is a major reservoir for calcium
• needs to be net mineralisation for bone growth to occur

Question 13

what has an influence on calcium

Answer 13

parathyroid and thyroid

Vit D

Question 14

what do parathyroid and thyroid do

Answer 14

regulate homeostatic calcium elvesl
paththyroud secretes parathyroid hormone
thryoid releases calcitonin

Question 15

parathyroid hormone

Answer 15

medium size peptide chain (84aa peptide)

• Ca2+ inhibits release
• low levels the hormone is released, causing breakdown of bone (osteolytic osteolysis) by osteoclasts
• causes increased synthesis of Vit D formation in kidney

Question 16

calcitonin released by

Answer 16

parafollicular cells

Question 17

calcitonin

Answer 17

• 32 aa peptide
• released when calcium levels are too high
• inhibits bone resorption
• stops calcium being removed from bone into the plasma
• may not really have a role in normal homeostasis, unknown

Question 18

Vit D

Answer 18

Allows SL absorption

• has to be hydroxylated 2 sides to make it an active hormone (1 AND 25 SIDE)
• upregulates carriers
• changes junctions (makes them more permeable to calcium)

Question 19

how can we synthesise Vit D

Answer 19

• can be formed from cholesterol
• therefore Vit D might not be considered a vitamin
• the receptor is a transcription factor, therefore can cause the activation and down regulation of other genes
• UV light allows us to synthesise vit D

Question 20

what does Vit D affect development and how

Answer 20

receptors present in developing bone

insufficient calcium prevents sufficient mineralisation of the bone

Question 21

Vit D and teeth

Answer 21

insufficient Vit D
enamel hypoplasia
enlarged pulp horns
elayed eruption
caries risk

prevention
- vit D and fluoride)

Question 22

how does Vit D affect burn turonver

Answer 22

Vit D able to ascite osteocalsts
increase plasma calcium levels
Vit D act indirectly with osteoblasts
osteoblasts release RANK ligand

Question 23

non skeletal roles of calcium

Answer 23

• cancer
• autoimmune disease
• hypertension and CVS disease
• diabetes
• muscle strength
• schizophrenia and depression

Question 24

osteomalacia and consequnces

Answer 24

lack of remineralisation

• pathological amount of callus matrix
• pseudo fractures
• bone pain
• muscle weakness
• periodontitis

Question 25

osteoporisis

Answer 25

low bone density in adults

Question 26

what is used to assess bone density

Answer 26

T score
0 is normal
lower the score lower the density

Question 27

pathogenesis of osteoporiris

Answer 27

reduced uptake of dietary calcium
imbalance of bone turnover
reduced bone density

Question 28

oestrogen in signalling (osteoporosis)

Answer 28

reduced inhibiton of osteoclasts

therefore bone broken down more

Question 29

prevention/treatment of osteoporosis

Answer 29

calcium and vit D tablets
alendrotnic acid can be prescribed (blocks osteoclast acvitivty)
weight bearing activity

Question 30

Vit D supplement amount

Answer 30

1000 IU/day