Brainscape's Knowledge GenomeTM

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


See full index

Renal System > Calcium, Phosphate, Magnesium > Flashcards

Calcium, Phosphate, Magnesium Flashcards

1
Q

Role of Phosphate in the body

A
  1. Constituent of bone

2. Urinary buffer for H+

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

T or F all plasma phosphate is filtered across the gomerulus?

A

FALSE

-only phosphate that is not bound to protein (90%) gets filtered through

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

How and where in the nephron is phosphate reabsorbed?

A

In the Proximal tubule only via an Na+-Phosphate cotransporter

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

Is there a limit to how much phosphate can be reabsorbed?

A

YES

  • reabsorption is saturable (similar to glucose)
  • once it reaches its saturation limit, the rest will be excreted
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Parathyroid hormone (PTH) effect on reabsorption of phosphate?

A

Inhibits reabsorption (promotes excretion) of Phosphate?

  • inhibits the Na-Phosphate cotransporter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

MOA of Parathyroid hormone (PTH) on reabsorption of phosphate

A

PTH binds basolateral receptor in proximal tubule cell, which is couple to Adenylyl cyclase via a Gs protein

  • AD converts ATP to cAMP which utimately leads to phosphorylation and inhibition of the Na-Phosphate cotransporter.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What in the urine would indicate that PTH is functioning?

A
  1. Increased Phosphate levels
  2. Urinary cAMP
    - cAMP is excreted through a luminal membrane transporter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Inherited disorder caused by a defect in the PTH receptor, it’s Gs protein, or adenylyl cyclase causes and inherited disorder called?

A

Pseudohypoparathyroidism

  • renal cells are resistant it PTH action despite elevated levels
  • Leads to phosphate and cAMP wasting
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where is calcium found in the body?

A

99% within the bone

  • rest in the ICF and ECF
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What regulates the amount of Calcium in the plasma?

A

PTH

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

Compare the reabsorption of calcium to that of sodium

A

Pattern of reabsorption is similar:

  • about 99% reabsorbed
  • Na and Ca reabsorption coupled in the PT and LOH
  • NOT couple in the DT!
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the filtration of calcium

A

Only the calcium that is not bound to plasma proteins may get filtered

  • 60% of plasma calcium not bound and can get filtered
  • filtered load = GFRxP[Ca]x.60
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What happens to calcium when Na+ reabsorption is inhibited in the proximal tubule?

A

Calcium is also inhibited

- they are coupled in the PT

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

How is calcium reabsorbed in the Thick AL of the LOH?

A

Paracellular reabsorption driven by the lumen-positive potential difference generated by the Na/K/2Cl - cotransporter

  • important for loop-diuretic action
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Effect of loop-diuretic on calcium reabsorption?

A

Inhibit Ca reabsorption to the same extent as sodium reabsorption
- via blocking the Na/K/2Cl - cotransporter

  • loop diuretics also helpful in tx of hypercalcemia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

3 special features of Ca reabsorption in the DISTAL tubule?

A
  1. DT is the only nephron segment where Na and Ca are NOT coupled
  2. Ca reabsorption is regulated by PTH
  3. Thiazide diuretics have opposite effect as the other classes of diuretics in regards to Ca reabsorption
17
Q

Effect of PTH on calcium reabsorption? Where does this occur?

A

PTH increases reabsorption in DT

- via a basolateral receptor called TRPV5

18
Q

The effect of PTH on the nephron?

A
  1. Decreases Phosphate reabsorption (PT)

2. Increases Calcium reabsorption (DT)

19
Q

Thiazide diuretics effects on calcium reabsorption?

A

Increase Ca+ reabsorption

  • decreases excretion through urine and thus the likelihood of Ca2+ stone formation
20
Q

Once reabsorbed, how does calcium get across the basolateral membrane?

A
  1. Na+/Ca2+ exchanger (NCX1), 2. Plasma membrane ATPase (PMCA1b
21
Q

Effect of Klotho protein on calcium in the nephron?

A
  1. Enhances TRPV5 receptor (Luminal)

2. Klotho enhances Na+/K+-ATPase surface expression that in turn activates NCX1-mediated Ca2+ efflux.

22
Q

Kidneys role in Vitamin D metabolism?

A

Calcidiol is metabolized to calcitriol (1,25(OH)2D) by the 1α-hydroxylase (CYP27B1) enzyme in the kidney.

23
Q

Effect of Calcitrol (1,25(OH)2D) on PTH?

A

Calcitrol inhibits transcription of PTH in parathyroid tissue

24
Q

How is the 1α-hydroxylase (CYP27B1) enzyme in the kidney regulated?

A
  • Inhibited by:
    1. Calcitrol (via VDR)
    2. FGF23
  • activated by PTH!
25
Q

What stimulates parathyroid hormone?

A
  1. Decreased Plasma Calcium (via CaSR)
  2. Increased plasma Phosphate
  3. FGF23
26
Q

The total effects of PTH

A
  1. Increases Ca reabsorption
  2. Decreases phosphorus reabsorption
  3. Increases Calcitrol (1,25(OH)2D) production
  4. Increase bone calcium resorption
27
Q

Function of FGF23?

A
  1. Decreases phosphate reabsorption (phosphaturic)

2. Suppressor of 1-alpha hydroxylase in the kidney

Renal System (19 decks)

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