Calcium Physiology Flashcards

1
Q

what are the main functions of calcium

A

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

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2
Q

describe the second messenger action of calcium

A

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

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3
Q

describe the concentration of ionised calcium

A

1.2mmol/litre

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4
Q

what is the concentration of calcium bound to citrate

A

0.2mmol/litre

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5
Q

what are the forms of diffusible calcium

A

ionised calcium and bound to citrate

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6
Q

what are the forms of non diffisuble calcium

A

bound to protein

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7
Q

what is the concentration of calcium bound to protein

A

1.2mmol/litre

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8
Q

what is the total calcium concentration

A

2.6 mmol/litre

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9
Q

which molecules are involved in calcium homeostasis

A

parathyroid hormone
calcitonin
vitamin D

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10
Q

describe parathyroid hormone secretion

A

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

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11
Q

how does parathyroid hormone increase plasma calcium

A
  • 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
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12
Q

what happens in the kidneys to increase plasma calcium concentration

A

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

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13
Q

what is 1.25 hydroxyvitamin D

A

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

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14
Q

describe calcitonin secretion

A

produced from thyroid glands in resopnse to high plasma calcium concentration

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15
Q

how does calcitonin act

A

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

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16
Q

does calcitonin play a role in calcium homeostasis

A

not a major one

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17
Q

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

A

7-dehydrocholesterol

18
Q

what is vitamin D3

A

cholecalciferol, formed from dietary vitamin D and 7-dehydrocholesterol

19
Q

describe vitamin D production

A
  • 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
20
Q

describe the destination of calcitriol

A

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

21
Q

which hormones increase bone formation and bone mass

A

calcitonin
growth hormone
IGF
insulin
oestrogen
testosterone

22
Q

which hormones decrease bone mass through increasing bone resorption

A

cortisol
parathyroid homrone
thyroid hormones

23
Q

what do osteoblasts do

A

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

24
Q

what are osteocytes

A

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

25
Q

what are osteoclasts

A

large, multinucleated cells derived from macrophages, that resorb bone

26
Q

where do osteoclasts lie in bone

A

howships lacunae

27
Q

desribe hypocalcaemic tetany

A

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

28
Q

what is alkalosis

A

low calcium concentration

29
Q

what is hypocalcaemia

A

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

30
Q

what is osteitis fibrosa cystica

A

areas of demineralisation in the skull and leg bones

31
Q

what can hypoparathyroidism do to the teeth

A

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

32
Q

what can cause vtiamin D deficiency

A

dietary deficiency, or a failure to synthesise in the body

33
Q

what does vitamin D deficiency do to the body

A

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

34
Q

what does vitamin D deficiency cause in children

A

rickets

35
Q

what does vitamin D deficiency cause in adults

A

osteomalacia

36
Q

what is osteoporosis

A

decreased bone mass and density

37
Q

what is osteopetrosis

A

increased bone mass and density

38
Q

describe osteoporosis in patients

A

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

39
Q

what are the causes of osteoporosis

A

nutritional deficiency and corticosteroids

40
Q

describe osteopetrosis in patients

A

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