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calcium disorders Flashcards

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Biology 101 flashcards
1
Q

is calcium the most abundant mineral in the body

A

yes

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2
Q

what is the dietary calcium intake

A

25mmol/day

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3
Q

how much dietary calcium is lost and via what

A

20mmol/day in faeces

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4
Q

how much calcium does bones have

A

25,000mmol

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5
Q

how much calcium does extracellular fluid have

A

23mmol

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6
Q

how much calcium does plasma have

A

9mmol

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7
Q

how much calcium is taken in by kidneys and reabsorbed back into plasma

A

240mmol/day taken into kidney and 235mmol/day reabsorbed back. therefore, 5mmol/day of calcium is lost via renal loss

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8
Q

functions of calcium

A
  • strength- bones, teeth
  • nervous system- they release neurotransmitters
  • muscles- they initiate muscle contractions
  • cell adhesion- cadherins help cells attach to eachother
  • hormonal- they are the intracellular second messenger
  • enzymatic function- they are the coenzymes for coagulation factors
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9
Q

how is calcium needed in muscle contraction

A
  • action potential arrives at junction which causes the release of acetylcholine (neurotransmitter)
  • they bind to receptors causing an action potential to occur and then calcium being released from sarcoplasmic reticulum
  • for muscle contraction to occur the myosin head and actin need to interact
  • the calcium binds to troponin causing a change (unblocks binding sites)
  • therefore, actin and myosin heads interact causing contraction
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10
Q

how does muscle relaxation occur

A
  • the calcium detaches from the troponin and enters back into sarcoplasmic reticulum (via ATP)
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11
Q

what type of systems is calcium needed for

A
  • first phase of embryonic development
    (fertilisation)
  • nervous system
  • for insulin secretion
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12
Q

what are the different forms of calcium

A
  • free ionised calcium (47%)
  • protein bound (46%)
  • complexed calcium (7%)
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13
Q

describe free ionised calcium

A
  • its physiologically active
  • its regulated by homeostatic mechanisms
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14
Q

what is the normal calcium reference range

A
  • total calcium- 2.20-2.60 mmol/L
  • free ionised calcium- 1.20-1.37 mmol/L
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15
Q

what are the factors affecting calcium concentration

A
  • changes in albumin (plasma protein) concentration
  • changes in anion concentration
  • changes in acid-base (pH)
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16
Q

what type of calcium changes when there are changes in albumin

A

total calcium (2.20-2.60mmol/L)

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17
Q

what type of calcium changes when there are changes in anion conc and acid base abnormalities

A

free ionised calcium (1.20-1.37mmol/L)

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18
Q

describe what happens when there are changes in plasma proteins (albumin)

A
  • when there is decreased albumin there is less total calcium but the free ionised calcium doesn’t change.
  • this could be due to liver disease, malnutrition, nephrotic syndrome
  • when there is increased albumin the total calcium increases but the free ionised calcium doesn’t change
  • this is due to severe dehydration, infections
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19
Q

what is the equation for correction factor

A
  • if the albumin is less than 40 then:
    total calcium measured + (0.02 x (40-albumin))
  • if the albumin is more than 40 then:
    total calcium measured - (0.02 x (albumin-45))
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20
Q

describe changes in anion concentration

A
  • when anion (phosphate) concentration decreases (hypophosphatemia) then the free ionised calcium concentration increases
  • this is due to vitamin d deficiency and diuretic therapy
  • when anion concentration (phosphate) increases (hyperphosphatemia) then free ionised concentration decreases
  • this is due to vitamin d intoxication, renal failure and hypoparathyroidism
21
Q

describe changes in pH- acid base imbalance

A
  • when there is acidosis (low pH and high H+ ions) there is high free ionised calcium but the total calcium stays the same
  • when there is alkalosis (high pH and low H+ ions) there is low free ionised calcium but the total calcium stays the same
22
Q

what are the hormones that regulate calcium homeostasis

A
  • parathyroid hormone
  • calcitonin
  • calcitrol
23
Q

how is the parathyroid hormone synthesised

A
  • there is pre-pro-PTH which has 115 amino acids which then undergoes synthesis in the rough endoplasmic reticulum to for pro-PTH (90 amino acids)
  • pro-PTH then is processed in the golgi apparatus to form PTH (84 amino acids)
  • PTH is then packaged into parathyroid granules and released when calcium levels are low
24
Q

what fragment is on the PTH

A
  • N-terminal which is biologically active
  • c-terminal
25
Q

what is needed for the secretion of PTH from the granules

A

magnesium

26
Q

describe the synthesis of calcitriol

A
  • our skin has 7-dyhydrolcholesterol (provitamin D) and when sunlight hits our skin it converts it into previtamin D3
  • this converts into cholecalciferol (vitamin D3)
  • cholecalciferol (vitamin D3) then goes into the liver where an enzyme called 25 hydroxylase helps convert it into 25-hydroxylcholecalciferol
  • a dietary intake of vitamin D3 (fish) and vitamin D2 (supplements) goes into the liver
  • 25-hydroxylcholecalciferol then goes into the kidney where another enzyme called 1 hydroxylase convert it into 1,25-dihydroxycholecalciferol (calcitriol)
  • PTH also helps in the kidneys to convert into calcitriol
27
Q

what are the functions of calcitrol

A
  • increases calcium and phosphate absorption in the gut
  • increases renal tubular reabsorption of calcium
  • increases bone reabsorption (osteoclasts)
  • inhibits calcitonin
28
Q

when calcitriol binds to the calcitrol binding receptors in the small intestine what happens

A

it increases calcium binding protein and calcium transport into blood

29
Q

what inhibits calcitonin

A

calcitriol

30
Q

what will happen to the calcium regulation if there is no magnesium to secrete PTH

A

calcium regulation will be disrupted as magnesium is needed to release PTH

31
Q

what is the function of PTH in the body

A
  • bone: it increases osteoclast (breakdown bone) activity which therefore releases calcium into the plasma
  • kidney: increases calcium reabsorption and the production of 1,25-dihydroxycholecalciferol (calcitriol). decreases phosphate and bicarbonate reabsorption
  • intestines: increases calcium absorption. this is because it stimulates the production of calcitriol which binds to the intestine
32
Q

what is the function of 1,25-dihydroxycholecalciferol (calcitriol)

A
  • goes into gastrointestinal tract (GIT) and increases the absorption of calcium
  • helps calcium being released from the bones
  • also calcium reabsorption in the kidneys
33
Q

what is calcitriol (1,25-dihydroxycholecalciferol) derived from

A

from vitamin D

34
Q

what makes the synthesis of 1,25-DHCC become activated

A
  • increased PTH
  • decreased phosphate
  • decreased calcium
35
Q

what happens to 25-hydroxycholecalciferol when there are normal or high concentrations of calcium in the plasma

A

the enzyme 24-hydroxylase acts upon 25-hydroxycholecalciferol which leads to the formation of 24,25-dihydroxycholecalciferol which is an inactive form of calcitriol

36
Q

where is calcitonin synthesized

A

in the c cells of the thyroid gland

37
Q

what is calcitonin composed of

A

32 amino acid peptides

38
Q

what causes calcitonin to be released

A

when there is an increase in calcium

39
Q

what inhibits calcitonin from being released

A

when there is a decrease in calcium

40
Q

what is the function of calcitonin

A

opposite to PTH
- stops calcium from being released from the bone
- stops calcium from being reabsorbed in the kidneys
- decreases calcium absorption in the gut

41
Q

what type of conditions can people have for calcitonin to be prescribed

A
  • hypercalcaemia
  • osteoporosis
42
Q

what is the disorder called when you have low plasma calcium concentration

A

hypocalcaemia

43
Q

what is the disorder called when you have high plasma calcium concentration

A

hypercalcaemia

44
Q

describe what happens to different organs in body when there’s hypercalcaemia

A
  • increased absorption of calcium in the GIT
  • decreased renal extraction of calcium (absorb more calcium)
  • increased bone loss (osteoclats) so more calcium will be absorbed
45
Q

what are the causes of increased GIT absorption of calcium

A
  • excessive vitamin D intake
  • tuberculosis
  • acromegaly (1-hydroxylase activity in kidneys)
    these increase the calcitriol levels in the body
46
Q

what causes a decrease in renal excretion of calcium

A
  • thiazide diuretics (increased calcium reabsorption)
  • milk-alkali syndrome
47
Q

what causes an increase in bone loss (osteoclasts which leads to increased calcium reabsorption)

A
  • malignancy
  • primary hyperparathyroidism (overactive parathyroid gland = increased PTH released)
  • hyperthyroidism (increased osteoclast activity = increased bone reabsorption)
48
Q

what are the causes of hypocalcaemia

A

blood science (7 decks)

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