Calcium homeostasis Flashcards
What intracellular reactions is calcium important for?
- muscle contraction
- nerve cell activity
- activation of enzymes
- release of hormones through exocytosis
- blood coagulation
- cell membrane stability
What are the 3 pools of calcium?
1 - Bone
2 - Intracellular calcium
3 - Extracellular fluid
What is the importance of the GI tract in regulating calcium levels?
- source of calcium for the body
- absorption of across mucosa both passive diffusion and active transport pump
- pump becomes more active when dietary calcium is low
What is the importance of the kidneys in regulating calcium levels?
- route of calcium excretion
- most calcium reabsorbed only 2% lost
- distal tubules under hormonal control-sites of calcium regulation in kidney
What is the difference between the role of osteoblasts and osteoclasts
- osteoBlasts Build bone
- osteoClasts Consume bone
What is the parathyroid gland?
- the main organ involved in calcium and phosphate homeostasis
- secretes parathyroid hormone, PTH
What is the effect of PTH?
increase calcium and phosphate concentrations in the extracellular fluid
What is the effect of calcitonin?
decreases movement of calcium from bone, decreases extracellular fluid calcium
What is the effect of increased calcium on calcitonin?
increases release of calcitonin
What is the importance of Vitamin D?
stimulates synthesis of protein in mucosal cells to increase movement of calcium across gut
What are some causes of hypercalcemia? (severe >14/dl)
- malignancy
- hyperparathyroidism
- fungal disease
- osteoporosis
- chronic renal disease
- hypervitaminosis D
What are some causes of hypocalcaemia?
- post-thyroidectomy hypoparathyroidism
- chronic and acute renal failure
- ethylene glycol intoxication
What are the main target organs that regulate calcium homeostasis?
gut, kidney and bone
