12/1 Calcium Homeostatis

Question 1

what are the roles that Ca plays in the body

Answer 1

Muscle contraction (sarcoplamic reticulum); Synaptic transmission; Second messanger in signaling; Bone/teeth structure; Ation potentials (heart); blood clotting

Question 2

why vitamin K in infants?

Answer 2

vitamin K allows the reaction of the clotting protiens to bind to calcium and to then function

Question 3

what is the most basic role (simple animals have it) of calcium?

Answer 3

signalling molecule

Question 4

what would the body protect most if calcium becomes limited?

Answer 4

it would protect the signalling function of calcium and it would sacrifice the structural roles of calcium

Question 5

what organs balance Ca with the blood

Answer 5

balance with the bone, kidney and intestines.

Question 6

What is the biggest res. of ca in the body?

Answer 6

bone

Question 7

what is the normal blood level of Ca

Answer 7

1.2 mM free Ca

Question 8

what functions of intestines with Ca

Answer 8

intake from diet and secrete out of the stool

Question 9

what functions of the bone with ca.

Answer 9

big resvior, and constant bone remodeling

Question 10

what are the hormones the control Ca

Answer 10

parathyroid Hormone (PTH). Vitamin D. Calcitonin (not really in humans).

Question 11

What is the role of kidney in calcium control?

Answer 11

Provide vitamin D and excrete and reabsorb Ca

Question 12

where is the parathyroid gland?

Answer 12

at the back of the thyroid gland in the neck, by the pharynx.

Question 13

what would high calcium do to chief cells in the parathyroid gland

Answer 13

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

Question 14

what if low Calcium in the blood around the parathyroid

Answer 14

the chief cells would not be binding Ca at g-protien coupled receptor and this will allow PTH vesicles to be released

Question 15

what type of hormone is PTH?

Answer 15

peptide

Question 16

what type of control is active on PTH?

Answer 16

humoral control (blood control)

Question 17

what other hormones besides PTH are humoral control?

Answer 17

Insulin/glucagon (sense blood glucose)

Question 18

what type of hormones are not humoral that we have talked about?

Answer 18

Thyroxine (T4) thyroid hormone; Angiotenson; progesterone, estrogen, testosterone, corticol etc.

Question 19

the body has just released a lot of PTH what will happen?

Answer 19

it will lead to osteoclasts releasing more Ca from bone. stimulates reabsorbtion of Ca in the Kidney.

Question 20

why would PTH lead to kidney excretion of phosphate?

Answer 20

phosphate binds to Ca in the blood so if there is less phosphate there is more free Ca

Question 21

I can’t absorb but 10% of Ca in intestines, what signal is missing?

Answer 21

Calcitriol

Question 22

We have just diagnosed a parathyroid tumor, what symptoms will need to be controlled

Answer 22

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.

Question 23

I have just identified a patient as having hypoparathyroidism…what would the Ca and PTH levels look like for them?

Answer 23

they would have low Ca and low PTH

Question 24

I have just identified a patient as having primary hyperparathyroidism…what would the Ca and PTH levels look like for them?

Answer 24

they would have high PTH and high Ca; high hormone means high Ca

Question 25

I have just identified a patient as having PTH-independent hypercalcemia...what would the Ca and PTH levels look like for them?

Answer 25

they would have high Ca and low PTH; this means that there is high Ca without PTH causing it!

Question 26

I have just identified a patient as having secondary hyperparathyroidism...what would the Ca and PTH levels look like for them?

Answer 26

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!

Question 27

I have stayed inside and played warcraft and eat only crappy food! why do I have a problem with Ca levels?

Answer 27

Vitamin D lack!

Question 28

what role does vitamin D play for Calcium

Answer 28

Mainly for the absorption of calcium in the intestines and mino in the absorb from the bones and kidney

Question 29

what is the construction of vitamin D

Answer 29

it has three hydorxl groups (OH) that come from cholesterol, then from renal hydroxylation, and then in a second step from liver hydroxylation

Question 30

how would PTH lead to creation of vitamin D

Answer 30

it leads to the first hydroxylation of vitamin D in the renal system.

Question 31

how do we deactivate calcitriol (vitamin D)

Answer 31

by hydroxilating it again and then we pee it out! (4 OH is death to Vit. D)

Question 32

what does Vitamin D do in the body?

Answer 32

it interacts with a nuclear hormone receptor to lead to expression of genes that increase the absorbtion of calcium (mainly in the intestines)

Question 33

the three step dance of PTH

Answer 33

1. activate osteoclasts; 2. Increase reabsorption in kidney tubules; 3. Promote vitamin D production in kidney to lead to absoption in the intestines.

Question 34

what is the loss of ca in bones lead to in children?

Answer 34

rickets

Question 35

what is the loss of bone density due to loss of Ca due to loss of vitamin D in adults ?

Answer 35

it is osteomalacia (adult version of rickets)

Question 36

why do we need sun to get V. D?

Answer 36

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!

Question 37

what is the difference in osteoporosis and osteomalacia?

Answer 37

Perosis: weakening of previously constructed bone. Malacia: defect in bone building process!

Question 38

why would low vit. D lead to hyperparathyroidism?

Answer 38

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/