Exam 5: Calcium Metabolism

Question 1

What is the calcium distribution?

Answer 1

99% bones/teeth
1% intracellular
0.1% extracellular fluid/plasma

Question 2

What are the different types calcium in extracellular fluid/plasma?

Answer 2

Protein-bound (30-40%)
Ionized (50-60%; unbound)
Complexed

Question 3

Describe ionized calcium

Answer 3

Biologically active

Fraction dependent on pH

Question 4

Where is complexed calcium found?

Answer 4

Citrate
Lactate
Bicarbonate
Phosphate

Question 5

What are the functions of calcium?

Answer 5

Nerve impulses
Muscle contraction
Coagualtion

Question 6

What does calcium do for nerve impusles

Answer 6

Membrane stabilization

Question 7

What does calcium do for muscle contraction?

Answer 7

Release of AcCh at NMU
Skeletal
Smooth
Cardiac (ionotropic and chronotropic)

Question 8

99% of filtered calcium is normally reabsorbed by the renal tubules. 90% of that is reabsorbed in proximal tubules, loops of Henle, and early distal tubules. The remaining 10% is reabsorbed. What is different about this reabsorption?

Answer 8

It is very selective

Question 9

What are the target tissues of parathyroid hormone?

Answer 9

Bone
Kidney
Small intestine

Question 10

What does PTH do to bone?

Answer 10

Resorption (release of Ca, P from bone)

Effect on blood levels (increase Ca, increase P)

Question 11

What does PTH do to kidney?

Answer 11

Reabsorption of Ca (increase Ca)

Excretion of P (decrease P)

Question 12

What does PTH do to small intestine?

Answer 12

Increase vitamin D3

Increase Ca and P

Question 13

Where is P excreted from in the kidneys?

Answer 13

Proximal tubules

Question 14

What is the net effect of PTH on the kidneys?

Answer 14

Increase serum Ca

Decrease serum P

Question 15

What are the target tissues of calcitriol?

Answer 15

Small intestine
Bone
Parathyroid

Question 16

What does calcitriol do to small intestine?

Answer 16

Increase Ca

Increase P

Question 17

What does calcitriol do to parathyroid?

Answer 17

Decrease PTH

Question 18

What does calcitriol do to bone in large quantities?

Answer 18

Stimulates bone resorption
Increase Ca in blood
Increase P in blood

Question 19

What does PTH regulation involve?

Answer 19

Feedback inhibition

Question 20

What is PTH secretion decreased by?

Answer 20

Hypercalcemia

Calcitriol

Question 21

What is PTH secretion increased by?

Answer 21

Hypocalcemia

Hyperphoshatemia

Question 22

What does vitamin D cause?

Answer 22

Renal activation

Question 23

What is the most important site of vitamin D regulation?

Answer 23

Renal activation

Question 24

What enzyme is involved in renal activation?

Answer 24

1α-hydroxylase

Question 25

What does calcitriol increase in response to in renal activation?

Answer 25

Increased PTH | Decreased P

Question 26

What does calcitriol decrease in response to in renal activation?

Answer 26

Increased P

Question 27

In regulation, what does PTH increase in response to?

Answer 27

Decreased Ca | Increased P

Question 28

In regulation, what does PTH decrease in response to?

Answer 28

Increase Ca | Increase calcitriol

Question 29

What is the effect of PTH on the kidney?

Answer 29

Resorption, increase Ca | Excretion, decrease P

Question 30

What is the effect of PTH on the small intestine?

Answer 30

Increase calcitriol, which increases Ca and P

Question 31

What is the effect of PTH on bone?

Answer 31

Resorption, which increases Ca and P

Question 32

What secretes calcitonin?

Answer 32

Parafollicular cells (C cells) of thyroid

Question 33

What does calcitonin do?

Answer 33

Decrease Ca concentrations

Question 34

What are the effects of PTH on bone?

Answer 34

Decrease osteocytic membrane activity | Decrease osteoclast formation