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Endocrine Physiology > Calcium Homeostasis > Flashcards

Calcium Homeostasis Flashcards

1
Q

Calcium functions

A
  1. Signalling
  2. Blood clotting
  3. Apoptosis
  4. Skeletal strength
  5. Membrane excitability - decreases Na permeability
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2
Q

Hypocalcaemia

A
  • Increased neuronal Na permeability
  • Hyperexcitation of neurons
  • Tetany, asphyxiation
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3
Q

Hypercalcaemia

A
  • Decreased neuronal Na permeability
  • Reduce excitation
  • Cardiac arrhythmias
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4
Q

Calcium distribution

A
  • Calcified extracellular matrix of bone (99%)
  • Intracellular
  • Extracellular (free or bound to plasma proteins)
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5
Q

Alkalosis effect on free plasma calcium concentration

A

Increased pH, increased protein bound Ca, decreases free [Ca]

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6
Q

Acidosis effect on free plasma calcium concentration

A

Decreased pH, decreased protein bound Ca, increases free [Ca]

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7
Q

Total body calcium =

A

Calcium in (diet) - calcium out (kidneys/faeces)

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8
Q

Turnover of bone

A
  • Osteoblasts: build bone (lay down matrix and calcify)
  • Osteocytes: regulate osteoblasts/clasts
  • Osteoclasts: mobilise bone (H+ dissolve Ca)
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9
Q

Two hormones that increase [Ca2+] plasma

A
  1. PTH

2. Calcitriol

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10
Q

PTH mechanisms of action

A
  1. Stimulate osteoclasts
  2. Inhibit osteoblasts
  3. Increased Ca2+ reabsorption by kidney
  4. Increased phosphate excretion by kidney
  5. Increased calcitriol production by kidney (increases Ca2+ absorption)
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11
Q

Calcitriol production

A
  • Diet, UV, prolactin stimulates production of vitamin D from cholesterol derivatives
  • Liver and kidney produce calcitriol
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12
Q

Calcitriol mechanisms of action

A

Increased absorption of Ca2+: gut, renal, bone.

- Note: -ve feedback on PTH

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13
Q

Hormone that decreases [Ca2+] plasma

A

Calcitonin (from parafollicular/C cells of thyroid)

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14
Q

Calcitonin: structure, secretion and mechanism of action

A
  • Peptide hormone
  • Increased [Ca2+] plasma
  • Decrease osteoclast behaviour and increase renal secretion
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15
Q

Cortisol effect on calcium/bones

A
  • Inhibits osteoblasts
  • Increase renal excretion
  • Decreased SI absorption
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16
Q

Insulin effect on bones

A
  • Antagonises cortisol

- Increases bone formation

17
Q

Oestrogen effect on bones

A
  • Increases bone formation
18
Q

GH effect on bones

A
  • Increases bone formation
19
Q

Prolactin effect on calcium

A

Increases Ca absorption from gut by stimulating calcitriol synthesis

20
Q

Vit D deficiency

A
  • <20ng/ml
  • decreased sunlight, gut absorption
  • PTH maintains plasma [Ca2+] by bone resorption
  • Bones become soft -> rickets, osteomalacia

Endocrine Physiology (8 decks)

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