Card Set Information
What are the 3 main compartments in which Ca2+ is found?
bone (99%), soft tissues, extracellular fluid
2 functions of calcium.
structural (skeleton-hydroxyapatite), non-structural (regulatory ion)
Some of the non-structural functions of calcium. (5)
muscle contraction, hormone secretion, cell membrane stability, neuromuscular excitability, blood coagulation
3 portions of total Ca2+ in plasma.
protein-bound, ionized (active), complexed to anions (lactate, bicarb, Ph)
In acidosis, there is ________ binding of Ca2+ to proteins; in alkalosis, binding is __________.
decreased (increased plasma Ca2+); increased (decreased plasma Ca2+)
A decrease in plasma protein results in ________ total calcium; iCa2+ is __________.
Most Ca2+ absorption takes place in the __________, which can be... (2)
small intestine; paracellular (passive) or transcellular (active)
__________ absorption of Ca2+ is passive and conc-dependent; ___________ is active and conc-independent.
What are the 3steps to transcellular absorption?
1. apical entry- epithelial Ca2+ channel
2. cytoplasmic diffusion- calbindin
3. basolateral extrusion- Ca2+ATPase pump, Ca2+Na+ exchanger
Calcium excretion occurs through... (5)
fecal, renal, sweat, fetal, milk
Most Ca2+ is reabsorbed in the _________ by a _________ route; a small amount is reabsorbed in the _________ by a __________ route.
proximal tubule; paracellular; distal tubule; transcellular
3 hormones that control Ca2+ regulation.
(most important), calcitonin, Vit D
A fourth hormone involved in Ca2+ regulation that is induced in cancer patients.
What are the main, active cells of the parathyroid gland?
Chief cells produce ________ in response to ________.
What kind of receptor does PTH bind to?
7 transmembrane domain receptors (same as for Epi)
Describe the function of the calcium-sensing receptor with regard to PTH.
stimulation by Ca2+ inhibits PTH secretion
High Vitamin D inhibits __________ and decreases ___________.
PTH mRNA transcription; parathyroid cell proliferation
_______phosphatemia stimulates PTH secretion.
_______ concentrations facilitate calcium homeostasis.
PTH function in the kidney. (3)
increase reabsorption of Ca2+, increase Vit D synthesis, increase renal phosphate excretion
PTH function in bone.
induce resorption by binding to
, which secrete factors to activate osteoclasts
In the proximal tubule, PTH inhibits the _________ and causes __________.
Na+Ph co-transporter; Ph excretion
In the LoH, PTH increases the ___________.
paracellular transport of Ca2+ and Mg2+
In tubular cells, PTH increases _________ to activate __________.
1α-hydroxylase activity; Vit D
The receptor in bone for PTH is in ___________.
osteoblasts (activate osteoclasts to lyse/reabsorb bone)
The receptor in bone for calcitonin is in __________.
Calcitonin is produced in the _________ in response to __________.
thyroid gland; hypercalcemia
Describe the function of calcium-sensing receptor with regard to calcitonin.
stimulation by Ca2+ increases calcitonin secretion
Gut hormone that is a strong stimulation of calcitonin release.
Function of calcitonin. (1)
decreases osteoclast function/bone resorption
What is the receptor for calcitonin.
7 transmembrane domain receptor
In lactation, __________ is required for Ca2+ excretion/contribution to the milk; therefore, _________ is blocked.
bone resorption; calcitonin
_______ is required from bone and teeth formation.
Required for intestinal absorption and renal resorption of Ca2+ and Ph.
Vit D deficiency in growing animals is ________; it adults, it is ________.
What is the active hormone form of Vit D?
In circulation, Vit D is bound to _________.
vitamin D binding protein
Regulated enzyme in the kidney, which is require to activate vitamin D.
1-α hydroxylase (regulated by PTH, Ph, Ca2+, Vit D)
__________ binds to the same receptor as PTH.
Under normal conditions, PTHrP functions include... (3)
placental calcium transport, cartilage and dental development, mammary gland formatino
Excessive PTHrP secretion in cancer results in...
increased osteoclast function--> bone loss; increased renal Ca2+ reabsorption;