Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ENRE > Regulation of Calcium and Phosphate Metabolism > Flashcards

Regulation of Calcium and Phosphate Metabolism Flashcards

1
Q

Where is calcium distributed in the body?

What is the active form of calcium?

A

99% in bones and teeth

more in ICF than ECF

free, ionized Ca = active

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What percentage of total Ca is free ionized?

A

50%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the the normal calcium level for adults?

How does it differ in children?

A

in the 9s = btw 9 and 10 mg/dl

higher in teens/puberty age

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are indicators of hypocalcemia?

A

numbness and tingling, spontaneous twitching

chvostek sign = twitching of facial ms from tapping on facial nerve

trousseau sign = carpopedal spasm upon inflation of bp cuff

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What occurs to membrane potentials in hypocalcemia?

A

reduces threshold for na channels –> easier APs

can get hypocalcemic tetany

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What occurs to membrane potentials in hypercalcemia?

A

harder to get APs –> nervous sys depressed and reflex responses slowed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does plasma protein concentration affect Ca levels?

A

alter total Ca concentration in same direction (more protein, more total Ca)

no change in ionized Ca

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do changes in anion concetration affect Ca concentration?

A

changes fraction of Ca complexed w/ anions

if Pi increases, ionized Ca decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does acid base affect ionized Ca?

A

acidemia –> H+ take up spots on albumin –> more free calcium

alkalemia –> decreased free Ca

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

To maintain Ca balance, what occurs?

A

kidneys must excrete the same amount of Ca that is absorbed by the GI tract

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the relationship btw Ca and phosphate?

A

inversely related

extracellular concentration of Pi is regulated by same hormones that regulate Ca

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Where is Pi distributed?

A

85% in bone

84% of plasma is ionized

more in ICF than ECF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Where is PTH synthesized and secreted?

A

from chief cells of the parathyroid gland

main stimulus is decreased plasma Ca

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What type of hormone is PTH?

How is it synthesized?

A

peptide hormone

preproPTH(115 aa) –> proPTH (90 aa) –> PTH in golgi –> packaged in secretory granules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does Vit D do to PTH signaling?

A

down regulates PTH gene

stimulates CaSR gene –> PTH can more sensitively respond to Ca

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How does increased Ca influence PTH?

A

inhibits PTH synthesis and secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How do chronic hyper and hypocalcemia affect PTH?

A

chronic hyper –> decreased synthesis and storage of PTH, increased breakdown and relase of inactive fragments

chronic hypo –> increased synthesis and storage, hyperplasia of parathyroid glands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How does magnesium affect PTH?

A

parallel to Ca, but less significant effects

severe hypomagnesemia (seen in alcoholism) –> inhibition of PTH synthesis, storage and secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What type of receptor does PTH work on?

A

Gs GPCR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the actions of PTH on bone, kidney, and intestine?

A

Bone: increases bone resorption

kidney: decreased Pi reabsorption, increased ca reabsorption, increased urinary cAMP
intestine: increased Ca absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What type of hormone is Vit D?

A

steroid hormone

25 OH cholecalciferol = inactive circulating

1, 25 OH cholecalciferol = active

24,25 OH cholecalciferol = inactive

22
Q

How is Vit D activated?

A

via 1 alpha-hydroxylase in proximal tubule of kidney

23
Q

Where are PTH receptors located in bone?

What are its short and long-term actions?

A

on osteoblasts

short-term = bone formation

long-term = bone resorption indirectly via cytokines from osteoblast –> osteoclasts

24
Q

How does Vit D act on bone?

A

synergistically w/ PTH –> stim osteoclast activity and bone resorption

25
Q

What two important signals act on osteoclasts to promote bone resorption?

A

IL-6

Rank ligand

26
Q

What is M-CSF?

A

growth factor

induces stem cells –> differentiate into osteoclast precursors –> mononuclear osteoclasts –> mature multinucleated osteoclasts

27
Q

What are RANK and RANKL?

A

RANK = cell surface protein on osteoclasts and osteoclasts precursors

RANKL = cell surface protein produced by osteoblasts, bone lining cells, and apoptotic ostocytes

they bind –> osteoclasts form –> bone resorption

28
Q

What is OPG?

A

soluble protein made by osteoblasts

decoy receptor for RANKL –> inhibits RANKL/RANK and inhibits formation of osteoclasts and therefore resorption

29
Q

How does PTH act on the kidney to affect Pi?

A

In the Proximal tubule

PTH –> Gs receptor –> AC –> cAMP –> pKA –> inhibits Na-Pi symporter

Pi cannot be reabsorbed –> complements Ca increase from bone resorption

30
Q

How does Vit D Act on the intestines?

A

acts to stimulate calbindin synthesis –> helps Ca get reabsorbed

31
Q

How does PTH affect the kidney in general?

A

stimulates 1alpha-hydroxylase activity –> activates Vit D

stim Ca reabsorption by TAL and distal tubule

inhibits Pi reabsorption by proximal nephrons (represses NPT2a)

32
Q

How does PTH affect the small intestine?

A

no direct action

(indirectly increases Ca absorption via activating Vit D)

33
Q

How does Vit D act on the kidney?

A

stimulates NPT2a expression –> promotes Pi reabsorption by proximal nephrons

minimal actions of Ca

34
Q

How does Vit D act on bone?

A

sensitizes osteoblasts to PTH

regulates osteoid production and calcification

35
Q

What does calcitonin do?

A

receptors on osteoclasts –> decreases activity and number of osteoclasts –> decreases blood Ca and Pi (inihibits resorption)

reduces Ca uptake in kidneys

no role in min to min regulation of plasma Ca

36
Q

How does estrogen affect intestines and kidneys?

A

estradiol 17beta –> stimulates intestinal Ca absorption and renal tubular Ca reabsorption

37
Q

How does estrogen affect the bones?

A

estradiol 17-beta promotes survival of osteoblasts and death of osteoclasts = favors bone formation

women after menopause –> bone loss

38
Q

How do glucocorticoids affect Ca?

A

promote bone resorption (favor RANKL over OPG)

renal Ca wasting

inhibit intestinal Ca absorption

39
Q

What do you see in the urine of ppl w/ primary hyperpara?

A

excessive Pi, cAMP, and Ca

40
Q

What are the main symptoms of primary hyperpara?

A

stones, bones, and groans

hypercalcuria - stones

increase bone resorption

constipation

(increased PTH, Ca, and Vit D, low Pi)

41
Q

What occurs in secondary hyperparathyroidism?

A

low Ca –> increase in PTH secondary to this

caused by renal failure or Vit D deficiency

42
Q

What are the labs you would see in secondary hyperparathyroidism from renal failure or Vit D deficiency?

A

in both: high PTH, low Ca and Vit D

in renal failure: high Pi bc can’t excrete it

in Vit D def: low Pi

43
Q

What are common symptoms of hypopara?

A

most associated w/ low ca: muscle spasm or cramping, numbness and tingling

44
Q

What labs do you see in hypoparathyroidism?

A

low: pth, ca, vit d
high: Pi

45
Q

What is Albright hereditary osteodystrophy?

A

pseudohypopara type 1a

inherited AD

Gs for PTH in bone and kidney is defective –> low calcium and high Pi; increased PTH

46
Q

What are the labs and physical features you would see in Albright hereditary osteodystrophy?

A

high PTH and Pi

low Ca and Vit D

short stature, neck, obese, subcutaneous calcification, shortened metatarsals and metacarpals

admin of PTH –> no phosphaturia or increase in urinary cAMP

47
Q

What occurs in humoral hypercalcemia of malignancy?

A

tumors create PTHrP –> acts like PTH and stimulates the receptor

in urine: high Ca, Pi, and cAMP

in blood: high Ca, low blood Pi

low PTH and vit D (in cancer Vit D levels are normally suppressed)

48
Q

What is Familial hypocalciuric hypercalcemia?

A

AD disorder

inactive CaSR in parathyroid glands and ascending LOH –> decreased urinary Ca excretion and increased serum Ca

basically body can’t tell when your calcium is raised

normal to high PTH

49
Q

What are the congenital forms of rickets?

A

pseudoVit D-deficient rickets or Vit D dependent type I = decreased 1alpha-hydroxylase

type II = decreased Vit D receptor

either can’t make active Vit D or cells can’t use it

50
Q

What labs do you see in Vit D deficiency?

A

high: PTH, urine Pi and cAMP, bone resorption
low: Ca, Pi, and Vit D

51
Q

What can RANKL inhibitors be used to treat?

A

osteoporosis

52
Q

What is the cyp1a gene?

How is it regulated?

A

The gene for 1alpha-hydroxylase that activates Vit D in the kidney

PTH promotes scrip via Gs

Ca inhibits via Gi

ENRE (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions