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Renal Physiology > Sodium, Potassium, Phosphate, Calcium, Magnesium Balance - Bishop's Notes > Flashcards

Sodium, Potassium, Phosphate, Calcium, Magnesium Balance - Bishop's Notes Flashcards

1
Q

The thin descending limb…

A
  • permeable to water and small solutes - water out, solutes in
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2
Q

The thin ascending limb…

A
  • permeable to small solutes but NOT to water - solutes move out, water does NOT move
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3
Q

At the PCT, ______ of Na+ is reabsorbed

A

67%

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4
Q

At the thick ascending limb, ______ of Na+ is reabsorbed

A

25%

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5
Q

At the DCT, _______ of Na+ is reabsorbed

A

5%, then 3% at collecting duct

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6
Q

The early proximal tubule has a lumen charge of _____ and a blood charge of _____

A

-4 mV; 0 mV

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7
Q

What is absorbed/secreted at the early proximal tubule? It’s a real mess. (1)

A
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8
Q

What is absorbed/secreted at the late proximal tubule? This is where 67% Na+ has been reabsorbed. (2)

A
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9
Q

The thick ascending limb is… (3 things)

A
  • Electrogenic
  • Load dependent
  • Impermeable to water
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10
Q

Why is the thick ascending limb electrogenic?

A

K+ leaks back into the lumen.

Since it is electrogenic, it helps drive other solutes via the paracellular route (Ca, Mg, etc.)

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11
Q

What does the water impermeability of the thick ascending limb contribute?

A
  • Separation of water and solutes
  • Establish corticopapillary osmotic gradient
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12
Q

What is reabsorbed/secreted in the thick ascending limb? (3)

A
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13
Q

What is absorbed/secreted at the early distal tubule? (4)

A
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14
Q

The early distal tubule is… (2 things)

A
  • Load dependent
  • Impermeable to water (“cortical diluting segment”)
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15
Q

What is absorbed/secreted at the late distal tubule and collecting duct, for a principal cell? (5)

A
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16
Q

Water permeability at the late distal tubule and collecting duct is controlled by:

A

ADH (vasopressin)

17
Q

What is spironolactone?

A

Aldosterone antagonist; K+ sparing diuretic

18
Q

Aldosterone causes the distal tubule and collecting duct to…

A

Reabsort Na+ and secrete K+ (alters transcription and translation in principal cells)

19
Q

What is furosemide?

A

A powerful diuretic; inhibits the Na-K-2Cl symporter in the thick ascending limb

20
Q

What factors keep K+ constant?

A
  • Epinephrine
  • Insulin
  • Aldosterone
21
Q

What factors displace plasma K+?

A
  • Acid-base balance
  • Plasma osmolality
  • Cell lysis
  • Exercise
22
Q

____ K+ reabsorbed in PCT

____ K+ reabsorbed in thick ascending limb

____ K+ reabsorbed in laste distal tubule and collecting duct

A

67%; 20%; (only reabsorbed in low K+ diet)

There is variable secretion of K+ into the collecting duct as well.

23
Q

What is absorbed/secreted at the late distal tubule and collecting duct, for an alpha-intercalated? (5)

A

Aldosterone causes H+ secretion here (pee out acid)

24
Q

What are some causes of increased K+ secretion by the principal cells?

A
  • High K+ diet
  • Hyperaldosteronism
  • Alkalosis
  • Thiazide diuretics
  • Loop diuretics
  • Luminal anions
  • High tubular flow
  • High Na+ diet
25
Q

____ phosphate is excreted in the PCT

____ phosphate is excreted in the late proximal tubule

____ phosphate is excreted in the urine (buffer for urinary H+)

A

70%; 15%; around 15%

26
Q

Parathyroid hormone (PTH) inhibits…

A

Proximal tubule cotransporter, increasing PO4 excretion

27
Q

Hyperparathyroidism causes…

A

Phosphaturia, along with cAMP

28
Q

Ca2+ reabsorption parallels Na+, except for…

A

the distal tubule

29
Q

The thick ascending limb drives paracellular transport of Ca2+ by…

A

+ luminal potential

30
Q

Loop diuretics inhibit the Na+/K+/Cl- cotransporter (like spironolactone), which…

A

Disrupts the + potential

31
Q

What does PTH do?

A
  • Increase Ca2+ reabsorption in distal tubule
  • Decrease Ca2+ reabsorption in proximal tubule, along with PO4

The net effect is reabsorption

32
Q

____ Ca2+ is reabsorbed in the PCT

____ Ca2+ is reabsorbed in the thick ascending limb (decreased by furosemide)

____ Ca2+ is reabsorbed in the distal tubule/collecting duct (increased by PTH, thiazide diuretics)

A

67%; 25%; 8%

<1% excreted

33
Q

____ Mg2+ is reabsorbed in the PCT

____ Mg2+ is reabsorbed in the thick ascending limb (decreaed by furosemide)

____ Mg2+ is reabsorbed in the distal tubule and collecting duct

A

30%; 60%; 5%

about 5% excreted

34
Q

Loop diuretics inhibit Mg2+ reabsorption by ________ (in the thick ascending limb)

A

inhibiting the Na+/K+/Cl- transporter

Renal Physiology (3 decks)

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