12/1 Calcium Homeostatis Flashcards
what are the roles that Ca plays in the body
Muscle contraction (sarcoplamic reticulum); Synaptic transmission; Second messanger in signaling; Bone/teeth structure; Ation potentials (heart); blood clotting
why vitamin K in infants?
vitamin K allows the reaction of the clotting protiens to bind to calcium and to then function
what is the most basic role (simple animals have it) of calcium?
signalling molecule
what would the body protect most if calcium becomes limited?
it would protect the signalling function of calcium and it would sacrifice the structural roles of calcium
what organs balance Ca with the blood
balance with the bone, kidney and intestines.
What is the biggest res. of ca in the body?
bone
what is the normal blood level of Ca
1.2 mM free Ca
what functions of intestines with Ca
intake from diet and secrete out of the stool
what functions of the bone with ca.
big resvior, and constant bone remodeling
what are the hormones the control Ca
parathyroid Hormone (PTH). Vitamin D. Calcitonin (not really in humans).
What is the role of kidney in calcium control?
Provide vitamin D and excrete and reabsorb Ca
where is the parathyroid gland?
at the back of the thyroid gland in the neck, by the pharynx.
what would high calcium do to chief cells in the parathyroid gland
Calcium would bind to G-protien receptors and protein kinase A and Protien kinase C and this would lead to inhibition of PTH secretion by having an accumulation of PTH containing vesicles
what if low Calcium in the blood around the parathyroid
the chief cells would not be binding Ca at g-protien coupled receptor and this will allow PTH vesicles to be released
what type of hormone is PTH?
peptide
what type of control is active on PTH?
humoral control (blood control)
what other hormones besides PTH are humoral control?
Insulin/glucagon (sense blood glucose)
what type of hormones are not humoral that we have talked about?
Thyroxine (T4) thyroid hormone; Angiotenson; progesterone, estrogen, testosterone, corticol etc.
the body has just released a lot of PTH what will happen?
it will lead to osteoclasts releasing more Ca from bone. stimulates reabsorbtion of Ca in the Kidney.
why would PTH lead to kidney excretion of phosphate?
phosphate binds to Ca in the blood so if there is less phosphate there is more free Ca
I can’t absorb but 10% of Ca in intestines, what signal is missing?
Calcitriol
We have just diagnosed a parathyroid tumor, what symptoms will need to be controlled
increased PTH will lead to low calcium in bone and this could lead to osteoporosis and all of the bad things from high Ca in the blood.
I have just identified a patient as having hypoparathyroidism…what would the Ca and PTH levels look like for them?
they would have low Ca and low PTH
I have just identified a patient as having primary hyperparathyroidism…what would the Ca and PTH levels look like for them?
they would have high PTH and high Ca; high hormone means high Ca
I have just identified a patient as having PTH-independent hypercalcemia…what would the Ca and PTH levels look like for them?
they would have high Ca and low PTH; this means that there is high Ca without PTH causing it!
I have just identified a patient as having secondary hyperparathyroidism…what would the Ca and PTH levels look like for them?
they would have low Ca and high PTH. this could be from a low vitamin D and low Ca environment…PTH is trying but Ca is not being released!
I have stayed inside and played warcraft and eat only crappy food! why do I have a problem with Ca levels?
Vitamin D lack!
what role does vitamin D play for Calcium
Mainly for the absorption of calcium in the intestines and mino in the absorb from the bones and kidney
what is the construction of vitamin D
it has three hydorxl groups (OH) that come from cholesterol, then from renal hydroxylation, and then in a second step from liver hydroxylation
how would PTH lead to creation of vitamin D
it leads to the first hydroxylation of vitamin D in the renal system.
how do we deactivate calcitriol (vitamin D)
by hydroxilating it again and then we pee it out! (4 OH is death to Vit. D)
what does Vitamin D do in the body?
it interacts with a nuclear hormone receptor to lead to expression of genes that increase the absorbtion of calcium (mainly in the intestines)
the three step dance of PTH
- activate osteoclasts; 2. Increase reabsorption in kidney tubules; 3. Promote vitamin D production in kidney to lead to absoption in the intestines.
what is the loss of ca in bones lead to in children?
rickets
what is the loss of bone density due to loss of Ca due to loss of vitamin D in adults ?
it is osteomalacia (adult version of rickets)
why do we need sun to get V. D?
the Pre-Vit. D needs UV exposure to form the double bonds needed to make the vit. D structure that will then get hydroxylated by the renal and the liver!
what is the difference in osteoporosis and osteomalacia?
Perosis: weakening of previously constructed bone. Malacia: defect in bone building process!
why would low vit. D lead to hyperparathyroidism?
it would lead to a lack of Ca absorb in the intestines which would lead to a low serum Ca which would lead to more PTH release/
