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LSM3214 > Calcium > Flashcards

Calcium Flashcards

1
Q

What is the relationship between Ca2+ and Phosphate?

A

Negative!

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2
Q

What are the 3 forms in which calcium can exist in the body?

A

Free (ionised), complexed (bound to Phosphate), bound to protein

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3
Q

What are bones composed of?

A

Osteoids and hydroxyapatite crystals (Ca3(PO4)2)

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4
Q

What is bone remodelling?

A

A balance between bone deposition (formation) and resorption (removal)

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5
Q

What are osteoids?

A

Organic extracellular matrix

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6
Q

What is the function of osteoclasts?

A

Secretes HCl to dissolve the hydroxyapatite crystals, releasing Ca2+ and phosphate back to the ECF
(bone resorption)

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7
Q

What is the function of osteoblasts?

A

Secrete organic matrix (osteoids), within which the hydroxyapatite crystals precipitate (bone deposition)

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8
Q

What is the function of osteocytes?

A

Transfers Ca2+ to the ECF without destroying the bone structure

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9
Q

Why is Ca2+ important for neuromuscular membrane excitation?

A

Ca2+ is required for closure of Na+ channels
- low Ca2+ = Na+ channels open = diffusion of Na+ = more depolarisation = repeated transmission of impulse = high contraction

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10
Q

Why is Ca2+ important for cardiac and smooth muscle contraction?

A

Ca2+ is needed for to initiate and regulate cardiac muscle contraction

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11
Q

Why is Ca2+ important for blood clotting?

A

Ca2+ is needed for the activation of clotting enzymes

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12
Q

Under what circumstances is PTH secreted and what is its function?

A

PTH secretion is stimulated by low ECF Ca2+ levels and functions to increase plasma Ca2+ levels.

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13
Q

What secretes PTH?

A

PTH is secreted by parathyroid glands

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14
Q

How does PTH increase plasma Ca2+ levels?

A

Increased bone resorption
Increased kidney reabsorption of Ca2+
Increased intestinal absorption of Ca2+

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15
Q

What is the effect of PTH on plasma phosphate levels?

A

Increased Phosphate uptake into plasma
Decreased kidney reabsorption of phosphate

[To increase phosphate excretion –> to avoid crystalisation of phosphate and calcium, which will override the increased calcium levels]

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16
Q

What secretes calcitonin?

A

Parafollicular cells of the thyroid gland

17
Q

Under what circumstances is calcitonin secreted and what is its function?

A

Calcitonin is secreted in response to high ECF Ca2+ levels and functions to decrease ECF Ca2+ levels.

18
Q

How does calcitonin decrease plasma Ca2+ levels?

A

Decreased bone resorption
Decreased kidney reabsorption of Ca2+

19
Q

Does calcitonin have any effects on the intestines?

A

Up to now, no

20
Q

What is the effect of calcitonin on plasma phosphate levels?

A

Decreased phosphate reabsorption in kidneys to increase phosphate urinary excretion

21
Q

Which form of Vitamin D is active?

A

D3

22
Q

Where is vitamin D obtained from?

A

Diet or skin

23
Q

What is the biosynthesis of vitamin D3?

A

D3 (inactive) is converted to 25-OH-VitD3 by liver enzymes that add OH

25-OH-VitD3 is stored in hepatocytes until needed, then released into the blood

1alpha-hydroxylase in the kidney hydrolyses it into 1,25-OH-VitD3 (active!)

24
Q

What is the function of Vit D3?

A

Stimulates intestinal absorption of Ca2+!

25
Q

What is hypercalcemia?

A

Excess calcium

26
Q

What are causes of hypercalcemia?

A

Excess PTH secretion or hyper-parathyroidism

27
Q

What are symptoms of hypercalcemia?

A

Moans
Bones (bone pain)
Stones (pain in flank areas)
Groans (abdominal pain)

28
Q

What is hypocalcemia?

A

Low Ca2+ levels

29
Q

What are causes of hypocalcemia?

A

Decreased PTH secretion or hypo-parathyroidism

30
Q

What are treatments for hypocalcemia?

A

Treatment with synthetic PTH (uavailable)
Provision of vitamin D
Increased Ca2+ diet/supplements

31
Q

What is the trousseau’s sign to identify hypocalcemia?

A

During blood pressure measurement, absence of blood flow causes spasms of hand and forearm. muscles.

32
Q

What is the chvostek sign to identify hypocalcemia?

A

Tapping of facial nerve around cheek leads to twitching of lips to spasm of all facial muscles.

LSM3214 (5 decks)

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