Calcium Homeostasis Flashcards
What are the diverse roles of Calcium?
1) Signalling
2) Blood clotting
3) Apoptosis
4) Skeletal strength
5) Membrane excitability
What is the importance of regulating Calcium concentration?
Regulating calcium concentration is critical in order to ensure normal cellular activity:
- A decrease in calcium blood concentration will result in increased Na permeability, leading to hyperexcitation of neurons.
- An increase in calcium blood concentration will result in decreased Na+ permeability and lead to decreased levels of neuronal activity and depress neuromuscular activity.
What is the overall effect of PTH on plasma Ca2+ and phosphate concentrations?
1) PTH acts to increase Ca2+ concentrations in the plasma by stimulating osteoclasts to release Ca2+ and phosphate in bone.
2) PTH also acts to inhibit osteoblasts from depositing Ca2+ in bone.
3) PTH also ensures that Ca2+ is not excreted by the kidneys.
What effects does PTH have on renal formation of 1a, 25-dihydroxycholecalciferol?
PTH stimulates the kidneys to form 1a, 25-dihydroxycholecalciferol, which itself is formed from dietary vitamin D.
What is the effect of 1a, 25-dihydroxycholecalciferol on Ca2+ absorption from the gut?
1a, 25-dihydroxycholecalciferol promotes calcium absorption from the gut.
What is the effect of 1a, 25-dihydroxycholecalciferol on Parathyroid gland function?
Increased levels of 1a, 25-dihydroxycholecalciferol would result in reduced parathyroid gland function
What is the nature and function of calcitonin?
1) Calcitonin is a peptide hormone produced by the thyroid gland, and its secretion is controlled by increased Ca2+ plasma concentrations.
2) Its function is to reduce Ca2+ plasma concentrations, and It does this by binding to osteoclasts in order to prevent resorption of Ca2+ from bone and it also increases renal excretion of Ca2+ so preventing a further spike in Ca2+ levels.
