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2 MEH > 21 Calcium Metabolism > Flashcards

21 Calcium Metabolism Flashcards

1
Q

Name some cellular processes which require calcium?

A

Hormone secretion, muscle contraction, nerve conduction, exocytosis, intracellular metabolism

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2
Q

Between what range does the body carefully regulate calcium ion concentration?

A

1.0-1.3 mmol/L

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3
Q

Why is phosphate so important?

A
  • Part of ATP molecule
  • Has role in activating/deactivating enzymes
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4
Q

How do phosphate plasma levels differ from calcium plasma levels?

A

Phosphate levels- not strictly controlled. Levels fluctuate throughout the day.

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5
Q

How is the homeostasis of calcium and the homeostasis of phosphate linked? (2)

A
  1. Both=priniciple components of hydroxyapatite crystals (mineral of bone)
  2. Both regulated by PTH and calcitriol (+calcitonin)

Calcitrol=active Vitamin D

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6
Q

Which 3 organ systems do PTH, calcitrol and calcitonin act on to regulate calcium and phosphate levels?

A
  1. Bone
  2. Kidneys
  3. GI tract
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7
Q

What is shown in the following diagram?

A

Calcium distribution and balance values for a 70kg human

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8
Q

Where is most of the calcium found in the body located?

A

Bone (approx. 1kg)

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9
Q

What’s the total amount of calcium in the extracellular pool (approximately)?

A

1g

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10
Q

What is the typical dietary intake of calcium?

A

800-1200mg

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11
Q

The intestines both absorb and secrete calcium for removal from the body.

What is the approximate net intestinal uptake of calcium per day?

A

175mg/day

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12
Q

How much calcium does the bone deposit and reabsorb per day?

A

280mg

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13
Q

What is the approximate calcium excretion in urine per day?

A

175mg

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14
Q

How much calcium do the kidneys filter daily?

A

About 10,000 mg

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15
Q

What are the 3 forms in which calcium exists in the body?

A
  1. Free ionised species (45%) Physiologically active
  2. Bound to anionic sites on serum proteins (eg albumin)(45%)
  3. Complexed with low-molecular-weight organic anions (eg citrate/oxalate)(10%)
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16
Q

What is the total concentration (of all 3 forms of calcium found in plasma) of plasma calcium?

A

2.7mmol/L

17
Q

What happens if plasma levels alter (outside normal plasma ?

A

Hypocalcaemia:

  • Hyperexitability of nervous system
  • Paresthesia- tetany (intermittent muscular spasms)- paralysis-convulsions

Hypercalcaemia:

  • Kidney stone formation
  • Constipation
  • Dehydration
  • Kidney damage
  • Tiredness
  • Depression
18
Q

If PTH and Calcitrol are released, what wil happen to serum calcium concentrations?

A

Raise serum calcium concentration

19
Q

Which hormone (PTH or calcitrol) is involved in the short term regulation of serum calcium and which is involved in the long term regulation of serum calcium?

A

PTH= short term

Calcitrol= long term

20
Q

What are the 2 types Vitamin D prohormones?

A
  • vitamin D2: ergocalciferol
  • vitamin D3: cholecalciferol
21
Q

Where can we obtain vitamin D?

A
  • Sun exposure
  • Food
  • Supplements
22
Q

Why must Vitamin D which has been obtained undergo 2 hydroxylation reactions?

A

Because it is biologically inert- must be activated in body

23
Q

What is the Parathyroid related peptide and what does it do?

A

PTHrP= produced by tumour- may lead to hypercalcaemia

Causes:

  • increased calcium release from bone
  • reduced renal calcium excretion
  • reduced renal phosphate reabsorption

(HHM= Hypercalcaemia of malignancy)

Tumour often=

  • Breast
  • Prostate
  • Myeloma
24
Q

How do the actions of PTHrP and PTH differ?

A

PTH increases calcitrol concentration, PTHrP does not.

25
Q

Why is calcium important in the blood clotting cascade?

A

It is factor IV in the clotting cascade

26
Q

What is EDTA?

A

Calcium chelator (binds calcium in selective way)

27
Q

Fill in the missing labels:

A
28
Q

What organs does PTH target?

A
  1. Bone
  2. Intestines
  3. Kidney
29
Q

What are the symptoms of chronic hypercalcaemia?

A
  • Renal calculi
  • Kidney damage
  • Constipation
  • Dehydration
  • Tiredness
  • Depression

(Stone, moans, groans, bones)

30
Q

What are the symptoms of hypocalcaemia?

A
  • Hyperexcitability of neuromuscular junction
    • Lower serum calcium
    • Increased Na+ entry into neurones
    • Depolarisation-increased liklihood of AP
  • Pins and needles
  • Tetany (muscle spasms)
  • Paralysis
  • Convulsions

2 MEH (18 decks)

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