Week 8: Ca2+, Mg2+, and PO4- handling Flashcards
(57 cards)
Functions of intracellular [Ca2+]
- second messenger
- Muscle contractility
- Cell motility
Extracellular Ca2+ functions
- Excitation-contraction coupling in muscle
- Synaptic transmission
- Platelet function & coagulation
- Primary regulator of PTH secretion
Why are Ca2+ levels so tightly regulated
because it can effect the potentials of excitable cells
issue with Hypocalcemia and excitable cells
Spontaneous depolarization
Issue with hypercalcemia on excitable cells
Depolarization hurdle
Where is most of the Ca2+ in the body
99% of total body Ca2+ and 85% Phosphate contained within the skeleton (hydroxyapatite)
How does Ca2+ circulate
46% bound to albumin
6% bound to small anions (citrate, phosphate, lactate)
48% biologically free active Ca2+ in feedback loops
How is rapid release of Ca2+/Pi mediated
mediated by PTH and Vitamin D acting directly on osteoblasts and indirectly on osteoclasts to resorb the bone
Describe Ca2+ flux between body compartments
Describe the effect of pH, plasma protein & citrate on total & free Ca2+
corrected or adjusted total Ca2+
Describe the bone remodeling process
What happens when too much bone is resorbed?
Ca2+/Pi maintenance
Where are the PT glands located?
Transfusions and Ca2+
preservative is citrate and adding a lot of citrate to someone can soak up a person’s Ca2+
Overview of Ca/P maintenance
Describe PTH synthesis and Secretion
Describe how Ca2+ is sensed by the PT glands
Describe other factors regarding PTH secretion
How is PTH gene transcription regulated?
Calcitriol inhibits PTH gene transcription
Low plasma Mg2+ effects on PTH
stimulates secretion of PTH
High plasma Mg2+ effects on PTH
Inhibits secretion of PTH
Mg2+ depletion effects on PTH
Paralyzes secretion
(Mg2+ second messenger in relay from CaSR to PTH secretion ( ie hypocalcemia in neonates with diarrheal disease)
