Calcium Homeostasis

Front 1

Calcium is essential for the normal function of a number of biochemical processes

Back 1

1) Blood Coagulation
2) Enzymes activity
3) Apoptosis
4) Membrane/action potential
5) Exocytosis
6) Necrosis

Front 2

What kind of control is Calcium homeostasis primarily under?

Back 2

Hormonal

Front 3

Phosphorus is closely associated to calcium. You will find it in bones and also in the blood stream in a different form.

Back 3

Ionic phosphate in the blood (Pi instead of P)

Front 4

What affect does Vitamin D have on plasma Calcium and Phosphate?

Back 4

Increase Calcium
Increase Plasma

Front 5

What affect does Parathyroid Hormone have on plasma Calcium and Phosphate?

Back 5

Found on osteoblasts,
Increase Calcium
Decrease Plasma

Front 6

What affect does Calcitonin have on plasma calcium and phosphate?

Back 6

Decrease both

Front 7

Where are the PTH glands located? How many are there? What is the primary secreting cell?

Back 7

Posterior surface of the thyroid.

4

Chief

Front 8

What does Vitamin D do to PTH secretion?

Back 8

It inhibits Directly and Indirectly.

Directly: represesses the prepro-PTH gene

Indirectly: Negative feedback mechanism through plasma Ca regulation

Front 9

The PTH receptor is a ___ receptor

Back 9

G protein linked receptor

Front 10

When activated, the PTH receptor alters what?

Back 10

Increases cAMP
Increases Gq/11
Increases Phospholipase C

Front 11

Where is PTH released from

Back 11

1) Bone - Osteoblasts
2) Kidney - Proximal and Distal Tubules

Front 12

Vitamin D is classified as a steroid. What is its active form called

Back 12

Calcitrol

Front 13

Vitamin D is similar to PTH in that it has an effect on the kidneys and bones. But what else does it affect that PTH doesn't affect?

Back 13

Intestine

Front 14

What affect does Vitamin D have on plasma Calcium and Phosphate?

Back 14

Increase Calcium
Increase Plasma

Front 15

What affect does Parathyroid Hormone have on plasma Calcium and Phosphate?

Back 15

Found on osteoblasts,
Increase Calcium
Decrease Plasma

Front 16

What affect does Calcitonin have on plasma calcium and phosphate?

Back 16

Decrease both

Front 17

Where are the PTH glands located? How many are there? What is the primary secreting cell?

Back 17

Posterior surface of the thyroid.

4

Chief

Front 18

What does Vitamin D do to PTH secretion?

Back 18

It inhibits Directly and Indirectly.

Directly: represesses the prepro-PTH gene

Indirectly: Negative feedback mechanism through plasma Ca regulation

Front 19

The PTH receptor is a ___ receptor

Back 19

G protein linked receptor

Front 20

When activated, the PTH receptor alters what?

Back 20

Increases cAMP
Increases Gq/11
Increases Phospholipase C

Front 21

Where is PTH released from

Back 21

1) Bone - Osteoblasts
2) Kidney - Proximal and Distal Tubules

Front 22

Vitamin D is classified as a steroid. What is its active form called

Back 22

Calcitrol

Front 23

Vitamin D is similar to PTH in that it has an effect on the kidneys and bones. But what else does it affect that PTH doesn't affect?

Back 23

Intestine

Front 24

Where is Vitamind D synthesized

Back 24

Liver

Front 25

The major step in vitamin D production requires activation by ____ and also needs ____.

Back 25

Parathyroid Hormone

UV

Front 26

What conditions will stimulate Vitamin D production?

Back 26

PTH
Low ECF [Ca2+]
Low ECF [Pi]

Front 27

What will inhibit Vitamin D production?

Back 27

Vitamin D - self regulation negative feedback

High ECF [Ca2+]

Front 28

T/F: Does vitamin D regulate processes involved with bone resorption and deposition?

Back 28

True

Front 29

Which parts of the small intestine is Calcium absorbed in?

Back 29

duodenum and jejunem

Front 30

How does Vitamin D increase plasma calcium?

Back 30

It increases absorption at the small intestine. It does the same for ionic phosphate.

Front 31

Does PTH have an effect on plasma calcium and phosphate?

Back 31

Not really. It does INDIRECTLY by stimulating synthesis of vitamin D.

Front 32

Calcium absorption in the intestine depends on what?

Back 32

Na, K, and ATPase

The enterocyte extrudes Ca2+ across the basolateral membrane via a Ca2+ pump and an Na+/Ca2+ exchanger

Front 33

When the Ca2+ is inside the lumen of the enterocyte, is it in its free ionic form?

Back 33

No, it is attached to a calcium binding protein called, Calbindin. This will keep cytosolic calcium low so that the steep gradient for calcium influx is maintained.

Front 34

How is phosphate absorbed through the intestine?

Back 34

Na/Pi cotransporter on the apical membrane

Front 35

What are the THREE major distinct actions of PTH in the kidney?

Back 35

1) Increases Ca2+ reabsorption from the distal tubule

2) Decreases Pi reabsorption from the proximal tubule

3) Stimulates Vitamin D synthesis

Front 36

Vitamin D can control Ca2+ and Pi reabsorption in the kidney as well, how does it differ from PTH control?

Back 36

1) Regulation is weak
2) Pi Reabsorption is an indirect effect.
3) Ca2+ reabsorption is a direct effect

Front 37

Pi reabsorption is reduced by

Back 37

1) PTH
2) Plasma Volume Contraction
3) Alkalosis
4) Glucocorticoids

Front 38

Hydroxyapatite precipitates in an active or passive process?

Back 38

Passive

Front 39

Is the ratio of Ca/Pi greater than or less than 1?

Back 39

less than 1

Front 40

What are the salt components of bone?

Back 40

Ca2+, Mg, K, carbonates

Front 41

Ca2+ is exchanged between bone and ECF by two mechanisms.

What is the main regulator?

Back 41

1) Rapid response - bone fluid exchange with soluble bone salts
2) Slow response - bone remodeling

Main regulator being [Ca]

Front 42

Whats special about the osteoblast-osteoclast interaction?

Back 42

Osteoblats release factors that induce the osteoclasts to:
1) differentiate
2) activation (by RANKYL)

Front 43

How does an osteoclast resorb bone?

Back 43

1) Forms villus like projection
2) Release proteolytic enzymes and acids from villi dig out a cavity called the resorption pit.

Front 44

When osteoblasts are activated at the surface of bone, what does it secrete?

Back 44

1) alkaline phosphatase
2) Osteocalcin

Front 45

We can use urine sample to determine whats going on with bone activity. What kinds of things can we see?

Back 45

1) Increase in hydroxyproline and hydroxylysine indicate bone resorption (these are waste products from osteoclast activity)

2) Alkaline phosphatase and osteocalcin are indicators of bone formation.

Front 46

Alkaline Phosphatase and Osteocalcin in the blood indicates what?

Back 46

Bone formation

Front 47

What are the two Ca2+ mobilization processes that are biphasic?

Back 47

1) rapid - osteoCYTIC osteolysis
2) Slow - osteoCLASTIC

Front 48

Vitamin D action in bone causes:

Back 48

Indirect: Calcification (synthesis)

Direct: Via VDR receptor on osteoblasts

Front 49

How does calcitonin decrease blood plasma calcium and phosphate?

Back 49

It inhibits osteoclast activity

Decreases formation of new osteoclasts

Front 50

Ca2+ homeostasis in Low Ca2+ conditions have two responses as well. What are they?

Back 50

1) Rapid response - Through PTH, inhibit Ca2+ excretion. Stimulate osteolysis.

2) Slow response: PTH activates vitamin D synthesis in the kidney.

Front 51

Excessive Thyroid hormone will cause ...

Back 51

too much bone resorption and increases serum [Ca2+]

Front 52

Low Thyroid Hormone will cause..

Back 52

Delayed ossification of cartilaginous bone

Front 53

How do GC effect skeletal growth?

Back 53

Direct: GCs inhibit osteoblast bone-forming functions

indirectly: GCs reduce plasma Ca concentration and promote PTh-induced resorption of bone

Front 54

Hypocalcemia causes

Back 54

Neuromuscular diseases (depolarization of neurons) and tetany

Front 55

What is rickets?

Back 55

Failure of osteoid to calcify (soft bones)

Only seen in growing person. In the adult, it is called Osteomalacia. These people usually have chronic renal failure.