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Physiology- Renal > Renal 5: Tubular Functions Along Nephron > Flashcards

Renal 5: Tubular Functions Along Nephron Flashcards

1
Q

In the proximal nephron, there is high/low volume, high/low gradient pumping of solutes and water.

A

high, low

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2
Q

How much of a filtered load is typically reabsorbed in the proximal nephron?

A

2/3

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3
Q

What is the primary mechanism for reabsorption int he proximal tubule

A

Na+, K+, ATPase in basolateral membrane

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4
Q

What transporters exist in the apical membrane in the first half of the proximal tubule?

A

Na+/H+ antiporter : couples entry of Na+ with extrusion of H+ (H+ secretion also leads to sodium bicarb reabsorption)
Na+/Glucose symporter (SGLT2)

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5
Q

What transporters exist in the basolateral membrane in the first half of the proximal tubule?

A

Na+/K+ ATPase.
HCO3- transporter,
Glucose transporter (GLUT2)

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6
Q

How is Na+ mainly reabsorbed in the second half of the proximal tubule?

A

With Cl- both transcellular and paracellularly

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7
Q

What transporters exist in the apical membrane in the second half of the proximal tubule?

A

Parallel
Na+/H+ Antiporters
Cl-/anion antiporters
SGLT1 Na/glucose symporter (difference is 2Na per 1 glucose)

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8
Q

What happens to the H+ and anion in the tubular fluid of the second half of the proximal tubule?

A

Combine and reenter the cell

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9
Q

What transporters exist in the basolateral membrane in the second half of the proximal tubule?

A

Na+/K+ ATPase- Na+leaves cell and enters blood
K+/Cl- symporter- Cl- leaves cell and enters blood
GLUT1 glucose transporter

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10
Q

In what part of the proximal tubule is the Na/K ATPase located?

A

basolateral membrane, both halves

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11
Q

In what part of the proximal tubule is the SGLT2 located?

A

apical membrane, first half

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12
Q

In what part of the proximal tubule is the GLUT1 located?

A

basolateral membrane, 2nd half

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13
Q

In what part of the proximal tubule is the Na/H antiporter located?

A

apical membrane, both halves

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14
Q

In what part of the proximal tubule is the anion/Cl- antiporter located?

A

apical membrane, 2nd half

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15
Q

In what part of the proximal tubule is the K+/Cl- symporter located?

A

basolateral membrane, 2nd half

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16
Q

In what part of the proximal tubule is the SGLT2 symporter located?

A

apical membrane, 1st half

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17
Q

In what part of the proximal tubule is the GLUT2 transporter located?

A

basolateral membrane, 1st half

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18
Q

In what part of the proximal tubule is the HCO3- transporter located?

A

basolateral membrane, 1st half

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19
Q

Isosmotic Reabsorption

A

water reabsorption occurs in equal proportion wiht reabsorbed solutes

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20
Q

How is the driving force for osmotic reabsorption of water across the proximal tubule established?

A

Via transport of solutes into lateral interceullar space, causing the osmolality of this compartment to increase

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21
Q

How does the movement of solutes across the proximal tubule membranes affect osmosis?

A

It increases osmolarity on the basolateral side, favoring water transport to that side.

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22
Q

What is an important consequence of osmotic water flow in the proximal tubule regarding potassium and calcium ions?

A

They are entrained in the reabsorbed fluid and thereby reabsorbed by the process of solvent drag.

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23
Q

How much of filtered protein is reabsorbed in the proximal tubule?

24
Q

What are the 2 causes of complete protein reabsorption in the proximal tubule?

A

enzymatic degradation of proteins to amino acids

encapsulation of proteins by pinocytic processes

25
Q

What causes proteinuria?

A

saturation of the transport process results in protein appearing in the urine.

26
Q

What happens to organic cations and anions in the proximal tubule?

A

actively secreted.

27
Q

What effect does cimetidine have on procainamide plasma concentration?

A

Increases (vice versa as well)

28
Q

Why is drug toxicity a danger for the cations of cimetidine and procainamide?

A

They elevate the plasma concentration of each other

29
Q

In the distal nephron, the kind of pumping that occurs is low/high volume and low/high gradient.

30
Q

What fraction of filtered loads is typically reabsorbed in the distal nephron?

31
Q

What conditions indicate the urine/plasma osmolality ration in the distal nephron being < 1

A

low ADH, dilute pale urine

32
Q

What conditions indicate the urine/plasma osmolality ratio in the distal nephron being >1

A

high ADH, concentrated dark urine

33
Q

Is the tubular lumen potential in the distal nephron strong or weak? What does this mean in regards to tight junctions there?

A

strong(-40 mV), tight junctions don’t leak

34
Q

What is reabsorbed in the thin descending limb of the loop of Henle?

35
Q

What is reabsorbed in the thin ascending limb of the loop of Henle?

A

Na+ and Cl-

36
Q

What is not reabsorbed in the thin descending limb of the loop of Henle?

A

Na+ and Cl-

37
Q

What is not reabsorbed in the thin ascending limb of the loop of Henle?

38
Q

What is the prime mover in the loop of Henle?

A

Na+/K+ ATPase

39
Q

What channels are on the apical membrane in the thick ascending loop of henle?

A

K+ channel (ROMK)
1Na+-1K+-2Cl- Symporter (NKCC2)
Na+/H+ Antiport

40
Q

What channels are on the basolateral membrane in the thick ascending loop of henle?

A

Cl- Channel (C1CNKB)
Na/K ATPase
K+/Cl- Symporter

41
Q

What is Bartter’s syndrome caused by?

A

mutation in channels of ascending loop of henle?

42
Q

What channels are located in the early segment of the distal tubule?

A

apical: Na/Cl symporter
basolateral: Na/K ATPase, Cl channel

43
Q

what channels are located in principle cells of the distal tubule?

A

Apical: Na channels inward, K channels outward
Basolateral: Na/K ATPase, K channel outward

44
Q

What channels are located in intercalated cells of the distal tubule?

A

apical: H+ ATP pump, H/K ATPase
Basolateral: Cl-/ HCO3- channel (out)

45
Q

What happens to salt and water reabsorption and the RAA system when extracellular volume decreases?

A

v ECV –> ^RAA system –> ^AT-II –> ^H2O, Na+, H+, Cl- reabsorption in proxmal tubule

46
Q

What happens to salt and water reabsorption and the RAA system when extracellular volume increases?

A

^ ECV –> v RAA system –> v AT-II –> v H2O, Na+, H+, Cl- reabsorption

47
Q

How does aldosterone regulate salt and water reabsorption

A

^ AT-II or ^ plasma K+ => ^ Aldosterone => ^ reabsorption of Na+ and Cl- in thick ascending loop of Henle, distal tubule, and collecting duct

48
Q 
What is the effect of atrial natriuretic peptide on the following?
natriuresis
total peripheral resistance
Na+ reabsorption
ADH
A

increase
decrease
decrease
decrease

49
Q

How does ANP and Urodilatin regulate salt and water reabsorption

A

^ ECFV or ^ Blood Volume => atrial stretch => ^ ANP => ^ natriuresis => v total peripheral resistance and v reabsorption of Na+, Cl- and v ADH

50
Q

What happens to sympathetic nervous activity and Na+ reabsorption with decreased ECV?

A

v ECV => ^ symp. activity => ^ NE and E => ^ Na+ and Cl- reabsorption in proximal and distal nephron

51
Q

What happens to Na+ reabsorption with increased dopamine?

52
Q

What happens to dopamine activity and Na+ reabsorption with increased ECV?

A

^ ECV => ^ dopamine => v Na+ and Cl- reabsorption in PT

53
Q

How does increased GFR affect Na+ reabsorption?

A

^ GFR => ^ filtered load of glucose and AAs => ^ H2O and Na+ reabsorption in PT

54
Q

What happens to Na+ reabsorption with increased antidiuretic hormone?

A

Nothing. Reabsorbs water in collecting duct with no effect on Na+/Cl- excertion

55
Q

What happens to peritubular cap reabsorption when glomerular cap filtration increases?

56
Q

What is meant by glomerulotubular balance?

A

Despite variations in GFR, a constant fraction of Na+ and H2O are still reabsorbed from the proximal tubule.

57
Q

What are the 3 routes of water transport across the proximal tubule?

A
  1. solutes and water reabsorbed across apical membrane
    And then 2 paths:
  2. solute and water cross the lateral cell membrane.
  3. remainder enters interstitial space and flows into capillary.

Physiology- Renal (8 decks)

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