Calcium Flashcards
What is the normal range for calcium?
2.2 - 2.5 mM/l
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
Give three hormones involved in control of calciu levels in serum
Parathyroid HormoneVitamin D (calcitriol)Calcitonin
What does PTH do?
raises serum calcium.N.B. parathyroid glands located on the posterior wall of the thyroid gland.
What does vitamin D do?
produces calcitriol which raises serum calcium
What does calcitonin do?
produced by the thyroid gland and lowers serum calcium, however, seems inactive in humans
What are three places PTH and Calcitriol have an effect?
Bone, kidney, gut
What effects does PTH have in bone?
Induces osteoblasts to synthesise and secrete cytokines on cells surfaceCytokines stimulate differentiation and activity of osteoclasts and protects them from apoptosisPTH decreases osteoblast activity – bony surface now exposed to osteoclasts– clasts secrete acid which breaks down bone Ca2+ and Pi released into extracellular fluid
What effect does PTH have in kidney?
Prevents kidney stonesPTH increases Ca2+ reabsorption and reduces its excretionPi removed from circulation
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
What effect does calcitriol have on bone?
Induces osteoblasts to synthesise and secrete cytokines on cells surfaceCytokines stimulate differentiation and activity of osteoclasts and protects them from apoptosisPTH decreases osteoblast activity – bony surface now exposed to osteoclasts– clasts secrete acid which breaks down bone Ca2+ and Pi released into extracellular fluid
Wjat effect does calcitriol have on kidney?
Decreases urinary loss of Ca2+ by stimulating reabsorption
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 carrier3.Endocytosis and exocytosis of Ca2+ and CaBP comples
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.
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
