Calcium Physiology Flashcards
what are the main functions of calcium
bone and tooth structure
mineral store
action potentials
membrane excitability
second messengers
co factor in metabolic pathways
blood clotting
describe the second messenger action of calcium
acts in:
muscle for excitation contraction coupling
gland secretion
non steroid hormone action
describe the concentration of ionised calcium
1.2mmol/litre
what is the concentration of calcium bound to citrate
0.2mmol/litre
what are the forms of diffusible calcium
ionised calcium and bound to citrate
what are the forms of non diffisuble calcium
bound to protein
what is the concentration of calcium bound to protein
1.2mmol/litre
what is the total calcium concentration
2.6 mmol/litre
which molecules are involved in calcium homeostasis
parathyroid hormone
calcitonin
vitamin D
describe parathyroid hormone secretion
produced from the parathyroid gland in resopnse to low plasma calcium concentration
how does parathyroid hormone increase plasma calcium
- increase resorption of bone through osteoclast activity
- increase calcium resorption in the kidneys with a decrease in phosphate resorption
- increased uptake of calcium from the intestines, with the assistance of vitamin D
what happens in the kidneys to increase plasma calcium concentration
increased formation of calcitriol (active vitamin D)
increased calcium resorption
increased phosphate excretion
what is 1.25 hydroxyvitamin D
this is the most active form of vitamin D known as calcitriol
describe calcitonin secretion
produced from thyroid glands in resopnse to high plasma calcium concentration
how does calcitonin act
lowers plasma calcium by increases the formation of bone through osteoblastogenesis and a decrease in calcium resorption in the kidney
does calcitonin play a role in calcium homeostasis
not a major one