Regulation Of Ca And PO4 Metabolism

Question 1

Calcium distribution in the body 
ECF
Plasma
ICF
Bones and teeth

Answer 1

.1% ECF
.5% plasma
1% ICF
99% bones and teeth

Question 2

In the plasma, Ca exists in _____ form complexed to anions or ____ form bound to plasma proteins

Answer 2

Non-ionized form complexed to anions

Ionized form bound to plasma proteins

Question 3

Ways to alter the concentration of Ca in the plasma

Answer 3

1. Alter total Ca - changes in plasma protein concentration alter total C concentration
2. Alter anion concentration
3. Alter Ca fraction bound to proteins

Question 4

What plasma protein binds Ca in the serum

Answer 4

Albumin

Question 5

In acedimia, albumin preferentially binds _____, thereby increasing ionized _____ in the serum

Answer 5

Albumin will bind H+ so more Ca is ionized

Question 6

In alkalemia, albumin prefferentially binds _____, thereby decreasing the concentration of ionized _____ in the serum

Answer 6

Preferentially binds Ca so will decrease the concentration of ionized Ca

Question 7

______calcemia increases neuromuscular excitability leading to tetany/spasticity

Answer 7

Hypocalcemia

Question 8

_____calcemia depresses neuromuscular excitability by what mechanism

Answer 8

Hypercalcemia shifts the threshold away from membrane potention

Question 9

Regulators of plasma calcium concentration

Answer 9

PTH
Calcitonin
Calcitriol

Question 10

Causes of low serum calcium

Answer 10

Hypoparathyrroidism
Renal disease
Vitamin d deficiency

Question 11

Organs invovled in the regulation of Ca

Answer 11

Bone
Kidney
Intestines

With three hormones
PTH
Calcitriol
Calcitonin

Question 12

Extracellular concentration is _______ correlated to that of Ca
EC concentration of Pi is regulated by the same hormones as Ca

Answer 12

Inversely correlated to Ca 2+

Question 13

Regulators of phosphate metabolism

Answer 13

Diet
Calcitriol increases plasma
PTH increases plasma []
Renal tubular resorption

Question 14

FGF23 is derived from

Answer 14

Bone

Question 15

Factors that regulate fgf23

Answer 15

Phosphate and VitD

Question 16

Effects of FGF-23

Answer 16

Directly downregulates NaPi transporters in kidney

Stimulates PTH to downregulate NaPi transporters in kidney

Decreases calcitriol production in the kidney

Question 17

FGF23 is secreted from the bone in response to

Answer 17

PTH
Calcitriol
Hyperphosphatemia

Question 18

FGF23 has what effect on Pi

Answer 18

Increases Pi excretion

Slows down resorption

Question 19

Potent regulator of Pi and Ca homeostasis synthesized and secreted from chief cells of what gland

Answer 19

Parathyroid hormone

Secreted from chief cells of parathyroid glands

Question 20

PTH secretion is stimulated by what factors

Answer 20

Low plasma (ionized) [Ca2+]

Question 21

How can the [Ca2+] in the plasma be sensed?

Answer 21

CaSR
Calcium sensing receptor

If a low [Ca] is senses, PTH secretion is induced by the receptor through Gq protein signaling

If high [Ca] os sensed, PTH secretion is inhibited by Gi protein

Question 22

Vitamin D has what effect on the expression of PTH and CaSR

Answer 22

Vitamin D inhibits both these factors

Question 23

Chronic hypercalcemia has what effect on synthesis/storage of PTH

Answer 23

Decreases synthesis/storage of PTH

Breaks down any stored PTH, releases inactive PTH fragments into circulation

Question 24

Chronic hypocalcemia has what effect on synthesis/storage of PTH

Answer 24

Increases synthesis/storage

Results in hyperplasia of parathyroid glands

Question 25

In severe hypomagnesia, what occurs to PTH

Answer 25

Inhibits PTH synthesis, storage, secretion

Question 26

PTH receptor is what type of receptor, using what signaling cascade

Answer 26

GPCR A cAMP cascade An IP3/Ca2_ cascade

Question 27

Low plasma [Ca] increases secretion of what hormone

Answer 27

PTH

Question 28

Effects of PTH on bone, kidney, intestine

Answer 28

PTH increases bone resorption Increases Ca and Pi in blood Kidney - decreased Pi reabsorption, increased Ca reabsorption, increased urinary cAMP Intestine - increased Ca absorption (PTH stimulated kidney cells to make and release calcitriol, which acts on intestine) All increase plasma [Ca] to normal

Question 29

Functions of vitamin D

Answer 29

Promotes mineralization of new bone by increasing Ca and PO plasma concentrations Has opposing effects on Pi levels va action on kidney and intestine Increases Ca and Po44 products to promote mineralization of new bone

Question 30

Order of organs for vitD synthesis

Answer 30

Skin Liver Kidney

Question 31

Liver enzyme of vitD synthesis

Answer 31

25-hydroxylase

Question 32

Kidney enzyme of vitD sytnthesis

Answer 32

1alpha-hydroxylase CYP1a Forms active form of vitD

Question 33

1alpha hydroxylase is stimulated by what factors

Answer 33

Decreased [Ca] Increased PTH Decreased PO4