GERR Physiology > Calcium > Flashcards

Calcium Flashcards

(48 cards)

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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

Study These Flashcards
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

Study These Flashcards
A
  • animal derived sources

- ex: eggs, milk , cheese , tuna

22
Q

How is vitamin D synthesized

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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 )

Study These Flashcards
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

Study These Flashcards
A

1- PTH

2- low phosphate levels

25
What mediates the actions of Vitamin D
- Vitamin D receptor that's in the nucleus and membrane of cell
26
Explain Rickets and Osteomalacia and the causes
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
What is the difference between Rickets and Osteomalacia
- rickets is in children while osteomalacia is in adults
28
Effects of Rickets disease
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
What is the difference between osteoporosis and osteomalacia
- 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
People at risk of Vitamin D deficiency
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
How is calcitonin produced
- 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
What regulates calcitonin levels
- high calcium levels
33
Is calcitonin important
- not very important in humans
34
How oestrogen and testosterone influence bone
- decrease bone resorption - increase synthesis of protective substance preventing osteoclasts - increase 1alpha-hydroxylase
35
How GTH influence bone
- stimulate bone synthesis
36
How TH influence bone
- increase bone turnover | - excess can lead to osteoporosis
37
How prolactin influence bone
- increase renal Ca reabsorption and 1alpha-hydroxylase
38
How Glucocorticoids influence bone
- increase bone resorption and decrease bone synthesis
39
How inflammatory cytokines influence bone
- increase bone resorption
40
When is peak bone mass attained and when is it lost
- 20s and maintained until 40s | - bone is lost after 50 at 1% per year and even faster in women
41
What is the abnormal calcium levels
greater than 3.5 or less than 1.9
42
Explain what Hypocalcaemia is and its causes
- low serum calcium | - causes : hyperparathyroidism, pseudohypoparathyroidism, vitamin D deficiency
43
What is pseudohypoparathyroidism and hyperparathyroidism
- hyperparathyroidism: usually due to removal while undergoing thyroidectomy - pseudohypoparathyroidism: receptor problem causes body resistance to PTH
44
How is Hypocalcaemia diagnosed ( explain two methods in detail )
- 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
Explain what Hyperparathyroidism is and its causes
- increase in PTH levels | - causes : primary hyperparathyroidism , secondary hyperparathyroidism , tertiary hyperparathyroidism
46
What causes primary , secondary and tertiary hyperparathyroidism
- primary : problem with parathyroid , cancer - secondary : low calcium level due to kidney failure - tertiary : chronic secondary hyperparathyroidism where parathyroid glands keep secreting PTH
47
What are the clinical signs of Hyperparathyroidism
1- bone pain 2- kidney stones 3- GI disruption 4- CNS disturbances
48
What is a big diagnostic sign to distinguish between Hypercalcaemia and Hypocalaemia
- Hyper : short QT interval | - Hypo : long QT interval
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