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GERR Physiology > Calcium > Flashcards

Calcium Flashcards

1
Q

What maintains calcium homeostasis

A
  • regulated ion transport by GIT , bone and kidneys
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2
Q

How is calcium in the body , where is it absorbed and where is it excreted

A

1- intake from diet
2- absorbed in small intestine
3- excreted in kidneys

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3
Q

What is the main site of calcium storage

A
  • bone
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4
Q

What is the purpose of the exchangeable calcium pool on bone surface

A
  • buffers acute changes in calcium load depravation
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5
Q

Does ICF or ECF have a higher calcium concentration

A
  • ECF

- even though there is more calcium in body cells than in ECF , ICF of one cell has a lower calcium concentration

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6
Q

What is free calcium

A
  • metabolically active calcium
  • calcium that causes physiological effect
  • diffusible
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7
Q

Other than free calcium what are the other forms of calcium

A

1- diffusible bound to ions

2- non-diffusable bound to albumin or globulin

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8
Q

What are the two important variables to measure with calcium serum levels

A

1- Albumin concentration : increase = increase of calcium

2- PH : change equilibrium of albumin calcium complex

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9
Q

What happens to calcium when albumin concentration is low

A
  • higher percentage of total serum calcium will be free and metabolically active
  • so patient might not show signs of hypocalcaemia
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10
Q

What happens to albumin and calcium when PH decreases

A
  • H ions increase , displacing Ca from albumin molecule

- increased amount of free calcium

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11
Q

What are the physiological functions of calcium ( 9 )

A
  • bone and teeth
  • glycogen metabolism
  • protein metabolism
  • plasma membrane integrity
  • coagulation
  • nerve and cardiac excitability
  • muscle contraction
  • gene regulation
  • cell differentiation
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12
Q

How is Ca2+ homeostasis controlled

A

1- vitamin D :
2- parathyroid hormone : parathormone
3- calcitonin
- all acting on bones , gut and kidneys

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13
Q

What are the two names of active vitamin D

A
  • 1,25-dihydroxycholecalciferol

- calcitriol

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14
Q

Are the parathyroids in the thyroid gland

A
  • no they are separated by a capsule tissue
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15
Q

How many functional parathyroid glands are essential

A
  • at least half of one parathyroid gland is needed for body to function
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16
Q

Explain the manufacturing and release of parathyroid hormone

A
  • when calcium levels are low , calcium sensing receptors on chief cells will detect low levels
  • stimulate parathyroid hormone secretion
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17
Q

What are the regulators of Parathyroid hormone

A

1- low Calcium
2- high phosphate
3- low magnesium

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18
Q

Explain the actions of the Parathyroid hormone ( PTH )

A

Bone :
1- short term rapid exchange from bone pool to ECF
2- long term resorption through osteoclasts
Kidney :
1- reabsorption of calcium
2- excretion of phosphate
3- formation of 1,25-dihydroxycholecalciferol
Intestine :
1- calcium absorption

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19
Q

Describe the relationship between serum calcium concentration ( ionized ) and PTH secretion

A
  • low ionized calcium = high PTH levels
  • this will cause ionized calcium levels to increase until a point where PTH becomes reduced due to calcium levels becoming normal
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20
Q

What is the relationship between calcium and phosphate and why

A
  • reciprocal relationship
  • as one increases the other decreases
  • product of calcium and phosphate is insoluble so to prevent that from happening it’s reciprocal
21
Q

Sources of vitamin D in diet

A
  • animal derived sources

- ex: eggs, milk , cheese , tuna

22
Q

How is vitamin D synthesized

A
  • 7-dehydrocholesterol ( precursor molecule ) will interact with UV light to form vitamin D3 in skin
  • converted to active 1,25-dihydroxycholecalciferol form in kidneys
  • parathyroid hormone activates vitamin D in kidneys in PCT through enzyme 1 alphahydroxylase
23
Q

What are the actions of Vitamin D activation ( 5 )

A

1- Works on intestinal epithelium :
- upregulates calcium binding protein channel production
- increases calcium stimulated ATPase production
- increase alkaline intestinal phosphatase levels
2- calcium reabsorption in kidney
3- calcification and mineralization in bone
Overall effect : increases plasma calcium concentration
4- Immune response , reproduction , cell differentiation

24
Q

What regulates the production of Vitamin D

A

1- PTH

2- low phosphate levels

25
Q

What mediates the actions of Vitamin D

A
  • Vitamin D receptor that’s in the nucleus and membrane of cell
26
Q

Explain Rickets and Osteomalacia and the causes

A

Deficiency of Vitamin D
1- lack of dietary vitamin D or sunlight
2- malabsorption of fats ( vitamin D is fat soluble )
3- failure to form calcitriol ( chronic renal failure )
4- mutation of 1alpha-hydroxylase
5- mutations in VDR

27
Q

What is the difference between Rickets and Osteomalacia

A
  • rickets is in children while osteomalacia is in adults
28
Q

Effects of Rickets disease

A

1- Bowing outworks bones in legs
- lack of VD = lack of bone calcification and mineralization
-bones will be soft since calcium is what makes bones hard
- bones won’t be able to handle weight of torso
2- Teeth cavities
- due to teeth being soft

29
Q

What is the difference between osteoporosis and osteomalacia

A
  • in osteoporosis, bone material itself is normal but there is just too little of it
  • in osteomalacia, the bone material is abnormal since it hasn’t been mineralized properly so it’s soft
30
Q

People at risk of Vitamin D deficiency

A

1- Elderly
2- housebound people ( nursing homes or extended hospital stays )
3- people with darker skin since they require more sun exposure to make Vitamin D

31
Q

How is calcitonin produced

A
  • produced in thyroid glands by c-cells ( parafolicular cells)
  • increase in calcium levels = increase calcitonin secretion = inhibits osteoclastic activity = reducing bone resorption = decrease blood climb levels
32
Q

What regulates calcitonin levels

A
  • high calcium levels
33
Q

Is calcitonin important

A
  • not very important in humans
34
Q

How oestrogen and testosterone influence bone

A
  • decrease bone resorption
  • increase synthesis of protective substance preventing osteoclasts
  • increase 1alpha-hydroxylase
35
Q

How GTH influence bone

A
  • stimulate bone synthesis
36
Q

How TH influence bone

A
  • increase bone turnover

- excess can lead to osteoporosis

37
Q

How prolactin influence bone

A
  • increase renal Ca reabsorption and 1alpha-hydroxylase
38
Q

How Glucocorticoids influence bone

A
  • increase bone resorption and decrease bone synthesis
39
Q

How inflammatory cytokines influence bone

A
  • increase bone resorption
40
Q

When is peak bone mass attained and when is it lost

A
  • 20s and maintained until 40s

- bone is lost after 50 at 1% per year and even faster in women

41
Q

What is the abnormal calcium levels

A

greater than 3.5 or less than 1.9

42
Q

Explain what Hypocalcaemia is and its causes

A
  • low serum calcium

- causes : hyperparathyroidism, pseudohypoparathyroidism, vitamin D deficiency

43
Q

What is pseudohypoparathyroidism and hyperparathyroidism

A
  • hyperparathyroidism: usually due to removal while undergoing thyroidectomy
  • pseudohypoparathyroidism: receptor problem causes body resistance to PTH
44
Q

How is Hypocalcaemia diagnosed ( explain two methods in detail )

A
  • Chvostek’s sign to diagnose neuromuscular excitability followed by tetany : low Ca makes it easier for Na to enter cells = easy depolarization
  • Trousseau’s sign which is done by inflating sphygmomanometer above SBP which results to muscle contraction and flection of wrist and metacarpal joints
45
Q

Explain what Hyperparathyroidism is and its causes

A
  • increase in PTH levels

- causes : primary hyperparathyroidism , secondary hyperparathyroidism , tertiary hyperparathyroidism

46
Q

What causes primary , secondary and tertiary hyperparathyroidism

A
  • primary : problem with parathyroid , cancer
  • secondary : low calcium level due to kidney failure
  • tertiary : chronic secondary hyperparathyroidism where parathyroid glands keep secreting PTH
47
Q

What are the clinical signs of Hyperparathyroidism

A

1- bone pain
2- kidney stones
3- GI disruption
4- CNS disturbances

48
Q

What is a big diagnostic sign to distinguish between Hypercalcaemia and Hypocalaemia

A
  • Hyper : short QT interval

- Hypo : long QT interval

GERR Physiology (18 decks)

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