Session 11 - Calcium Metabolism Flashcards Preview

Semester 1 - Metabolism > Session 11 - Calcium Metabolism > Flashcards

Flashcards in Session 11 - Calcium Metabolism Deck (20):
1

What is the normal range for calcium?

2.2 - 2.5 mM/l

2

What is calcium used for?

Nerve transmissions (release of synaptic vesicles)
Builds and maintains bone (prevents osteoporosis)
Regulates heart rhythm
Assists blood clotting (released by platelets and aids carboxylation of glutamine)
Muscle contraction (released from sarcoplasmic reticulum and binds with TnC)
Kidney function

3

Give three hormones involved in control of calciu levels in serum

Parathyroid Hormone
Vitamin D (calcitriol)
Calcitonin

4

What does PTH do?

raises serum calcium.N.B. parathyroid glands located on the posterior wall of the thyroid gland.

5

What does vitamin D do?

produces calcitriol which raises serum calcium

6

What does calcitonin do?

produced by the thyroid gland and lowers serum calcium, however, seems inactive in humans

7

What are three places PTH and Calcitriol have an effect?

Bone, kidney, gut

8

What effects does PTH have in bone?

Induces osteoblasts to synthesise and secrete cytokines on cells surface
Cytokines stimulate differentiation and activity of osteoclasts and protects them from apoptosis
PTH decreases osteoblast activity – bony surface now exposed to osteoclasts
– clasts secrete acid which breaks down bone
Ca2+ and Pi released into extracellular fluid

9

What effect does PTH have in kidney?

Prevents kidney stones
PTH increases Ca2+ reabsorption and reduces its excretion
Pi removed from circulation

10

What effect does PTH have in gut?

PTH stimulates conversion of vitamin D, in kidney, to its active form Calcitriolwhich increases uptake of Ca2+ from the gut

11

What effect does calcitriol have on bone?

Induces osteoblasts to synthesise and secrete cytokines on cells surface
Cytokines stimulate differentiation and activity of osteoclasts and protects them from apoptosis
PTH decreases osteoblast activity – bony surface now exposed to osteoclasts
– clasts secrete acid which breaks down bone
Ca2+ and Pi released into extracellular fluid

12

Wjat effect does calcitriol have on kidney?

Decreases urinary loss of Ca2+ by stimulating reabsorption

13

What effect does calcitriol have on gut?

1.Active uptake of Ca2+ on brushborder of small intestine (greatest in the duodenum and jejunum)
2.Transcellular transport with CaBP carrier
3.Endocytosis and exocytosis of Ca2+ and CaBP comples

14

How does PTH interact with vitamin D, and what does this enable?

PTH stimulates the conversion of vitamin D to its active form (calcitriol) by stimulating renal C-1 hydroxylase activity. Enables calcitriol to oversee the absorption of Ca2+ in the gut.

15

Explain regulation of PTH and vitamin D

Changes in [Ca2+] alter PTH and vitamin D activity via negative feedback

Chief cells (parathyroid) has unique calcium protein receptors on the cell surface; calcium binds; reduced camp; reduced PTH release

16

What is the significance of renal function on calcium metabolism

Prevents the occurrence of kidney stones mainly by the action of PTH

Kidneys are able reabsorb Ca2+ which has been filtered

17

What are the causes of hypercalcaemia?

Malignancy: tumours produce PTHrP which activates osteoclasts but NOT renal C-1 hydroxylase

18

What are the symptoms of hypercalcaemia?

Kidney stones
Constipation
Dehydration (increased urine output due to high ion concentration)
Kidney damage
Tiredness (neurologic)
Depression (neurologic)

19

What are the causes of hypocalcaemia?

Hypoparathyroidism (uncommon)
Accidental surgical removal of parathyroid gland

20

What are the symptoms of hypocalcaemi?

Rickets/osteomalacia – pliable bones
Hyper-excitability in the nervous system
Hyper-excitability in the neuromuscular junction – paraesthesia (burning and prickling sensation in the extremities)
Tetany – paralysis – convulsions