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5 bone biology > calcium homeostasis > Flashcards

calcium homeostasis Flashcards

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1
Q

what is the principal hormone for the regulation of plasma sodium and potassium ion concentrations

A

aldosterone

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2
Q

how does calcium influence enrves

A

Calcium can signal neurotransmitters from nerve terminals

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3
Q

how does calcium influence muscles

A

a reduced level of calcium then there will be decreased neuromuscular activity leading to muscle spasms

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4
Q

what can cause muscle spasms

A

hypocalcaemia

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5
Q

why can hypocalcaemia cause muscle spasms

A

As there are more calcium ions inside compared to outside there is an increase in

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6
Q

explain the mechanisms of action of the effect of calcium in muscle contraction

A

AP increase calcium permeability
entry of calcium into cardiac and smooth muscle cells triggers contractile mechanism

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7
Q

how will an increase in cytosolic calcium influence muscle

A

cause contraction

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8
Q

how will an increase in extracellular fluid calcium influence muscle

A

decrease likelihood of contraction due to decreased neuromuscular excitability

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9
Q

is plasma [Ca2+] regulated in a wide or narrow range

A

very carefully regulated in a narrow rage (2.2-2.6 mol/L)

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10
Q

what is phosphate crucial in

A

the activation and deactivation of enzymes (kinases and phosphates)

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11
Q

what enzymes is phosphate crucial in activating and deactivating

A

kinases and phosphates

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12
Q

what are the principle components of hydroxyapatite crystals in bone

A

calcium and phosphate

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13
Q

what 3 hormones regulate calcium and phosphate

A

parathyroid hormone
1,25- dihydroxyvitamin D
calcitonin (less)

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14
Q

what systems are influenced by parathyroid hormone
1,25- dihydroxyvitamin D
calcitonin

A

bone kidneys and GI

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15
Q

if parathyroid hormone , 1,25- dihydroxyvitamin D or calcitonin lowered calcium what would you expect its influence on phosphate to be

A

could either raise or lower it - the actions can be opposite for calcium and phosphate

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16
Q

what is a decrease is plasma calcium ion concentration known as

A

hypocalcemia

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17
Q

what is the main regulator of PTH

A

plasma calcium ion concentration

18
Q

what would decrease in plasma calcium ion concentration do to PTH

A

stimulate secretion

19
Q

how many parathyroid glands do humans have

A

4

20
Q

where are parathyroid glands located

A

either side of thyroid gland

21
Q

what cells synthesise and secrete PTH

A

chief cells

22
Q

where are chief cells located

A

parathyroid gland

23
Q

what is the effect of PTH modifying trans-epithelial transport

A

stimulates renal Ca2+ reabsorption and inhibits renal phosphate reabsorption

24
Q

what are the actions of 1,25-dihydroxyvitamin

A

enhance renal Ca reabsorption
enhance Ca absorption by small intestine
modulate movement of Ca and phosphate in and out of the bone

25
Q

how can PTH influence bone on a cellular level

A

can promote resorption (osteoclasts) or deposition (osteoblasts)

26
Q

what are the two forms that vit D exists in the body

A

D3 and D2

27
Q

why can vit D be considered a hormone

A

it is endogenously synthesised

28
Q

what version of vit D has a role in calcium balance

A

activated form of vit D

29
Q

what is the action of activated vit D

A

raise plasma concentrations of both calcium and phosphate

30
Q

what is the biological action of 1,25- dihydroxyvitamin D

A

acts on small intestine and kidney to raise plasma calcium ion concentration

31
Q

does PTH or 1,25- dihydroxyvitamin D have a more dramatic effect on the kidney

A

PTH

32
Q

where is vit D obtained from

A

diet and sunlight

33
Q

when vit D is absorbed what is its effect on calcium and phosphate levels

A

promotes intestinal absorption of Ca2+ and PO43-

34
Q

what is vit D deficiency in children

A

rickets

35
Q

what is vit D deficiency in adults

A

osteomalacia

36
Q

how does vit D deficiency lead to weekend bones

A

leads to impaired intestinal absorption of Ca2+ , hypocalemia increased PTH secretion, PTH leads to increased bone resorption

37
Q

what triggers release of calcitonin

A

hypercalcemia

38
Q

what is the action of calcitonin

A

lower plasma calcium ion concentration

39
Q

what does PTH act on and what’s the effect

A

acts on kidney and bone to increase plasma calcium ion concentration and lower plasma phosphate concentration

40
Q

what does 1,25- dihydroxyvitamin D act on and what’s the effect

A

acts on small intestine and kidney to increase plasma calcium concentration and increase plasma phosphate concentration

41
Q

is calcitonins role significant or minimal

A

minimal

42
Q

what does calcitonin act on and what’s its effect

A

acts on kidney and bone to lower plasma calcium concentration

5 bone biology (3 decks)

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