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Physiology Block 7 > Transport Along The Nephron > Flashcards

Transport Along The Nephron Flashcards

1
Q

Tube,are Rena, epithelial cells exhibit what

A

Membrane polarity

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2
Q

What side of the renal epithelial cells face the urine

A

Apical/tubular

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3
Q

What side of the renal epithelial cells faces the interstitial and peritubular caps

A

Basal/basolateral

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4
Q

How do the two side of renal epithelial cells differ

A
  • different transporters/channels
  • maintains a cxn gradient for movement of solutes
  • inside of cell maintains a low cxn of everything
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5
Q

What are the two ways solutes move in the kidneys

A

Paracellular or transcellular

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6
Q

Paracellular

A

Solutes move between the cells (filtration in normal caps)

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7
Q

Transcellular

A

Solutes move across the cell (transport protein or cx gradient)

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8
Q

Active transport

A

Against gradient

Uses ATP

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9
Q

Passive transport

A

With gradient and no atp

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10
Q

Simple diffusion

A

Due to gradient, also bulk flow (ultrafiltration)

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11
Q

Carrier mediated diffusion

A

Needs a carrier protein. Has a Tm

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12
Q

How much plasma does the kidney filter every day

A

180L

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13
Q

What is the minimum excretion of urine a day

A

0.5L a day

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14
Q

How much of what is filtered gets reabsorbeD?

A

Nearly everything. 99%

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15
Q

Ability to adjust reabsorption rate to match the filtered load

A

Glomerulotubular balance

If you eat too much salt, after a couple days your kidney will adjust to secrete more sodium

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16
Q

What happens when the pressure drops from glomerular to peritubular capillaries

A

Osmotic pressure rises

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17
Q

Net filtration from tubule INTO peritubular capillary

A

Starling forces

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18
Q

Where are the sealing forces relevant

A

PCT

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19
Q

Transport of OTHER solutes from tubule into caps will osmotically pull water along with it (water follows salt)

A

Osmosis

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20
Q

What happens to the osmotic pressure of caps if the RBF increases

A

Will not increase as much.

GFR increases, but reabsorption drops

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21
Q

Reabsorption of water (via paracellular filtration) will pull solutes along with it (Ca2+ and K+)

A

Solvent drag

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22
Q

Most Na+ movement is __________

A

Transcellular (active transport)

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23
Q

Reabsorption of Na and its cotransported solutes causes

A

Osmotic gradient. Reabsorbs water

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24
Q

What is the osmotic gradient created by reabsorption of Na and its cotransporters important for

A

-DM. Glucose has to be transports in with Na. Lose glucose in urine and increase osmotic pressure and pull out water

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25
Q

Something that isn’t supposed to be there keeping water in the tubules

A

Osmotic diuresis

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26
Q

What kind of transport on the baslateral membrane

A

Active transport

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27
Q

What is responsible for the active transport on the basolateral membrane

A

ATPase (3 Na out, 2 K in)

  • makes cell have neg charge relative to tubular fluid
  • osmotic gradient to pull water
  • forms a Na gradient bc apical side has no Na channels (impermeable)
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28
Q

What is the established gradient from the active transport at the basolateral membrane used for

A

Secondary active transport

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29
Q

What is Na reabsorbed wit h

A

Bicarbonate

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30
Q

What is required for the reabsorption of bicarbonate

A

Carbonic anhydrase

  • takes H+ and HCO3- and makes water and CO2. Takes the negative HCO3- which cant get across the membrane and turns it to CO2 and H20 so it can get it across
  • usually reabsorbed 100% HCO3
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31
Q

What is Na cotransported with

A

Glucose, amino acids, phosphates, lactate

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32
Q

Late PCT reabsorption of Na

A

No more glucose/ amino acids

-Na now gets cotransported with Cl- through the paracellular route as well as transcellular

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33
Q

What else other than CL- does Na get reabsorbed with in the late PCT?

A

When anions are secreted/exchanged for Cl-

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34
Q

What are some anions that are secreted/exchanged for Cl- in late PCT reabsorption

A

OH-, formate, oxalate, HCO3-

-binds H+ and neutralizes charge

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35
Q

Lack of filtered bicarbonate leads to what

A

Hyperchormia

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36
Q

What happpens to the lumen as CL- is removed and H+ neutralizes the OA_?

A

Becomes positive

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37
Q

Which of the following could explain why untreated diabetic patients have increases urine flow

A

Increases tubular fluid osmotic pressure

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38
Q

What effect would a carbonic anhydrase inhibitor have on urine volume and osmolarity

A

Increase volume, decrease osmolarity

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39
Q

Reabsorption of cations vs reabsorption of anions in the PCT

A

About equal

-we reabsorb a lot of Pi- and HCO3- at the expense of Cl-

40
Q

Movement of water vs the movement of sodium in the PCT

A

Matched

  • osmolality doesn’t change
  • PCT is isomotic bc of high water permeability
41
Q

What helps drive the paracellular reabsorption of cations late in PCT

A

Slight positive change in tubular fluid

42
Q

What does PCT secrete

A

Organic anions (-)

  • low specificity, high rate
  • 100% cleared in one pass
43
Q

What does PCT reabsorbs to excrete organic anions (PAH, penicillin)

A

A-ketoglutarate

44
Q

Are transporters selective or non selective

A

Non selective.

  • fast and low specificity
  • too much of one organic anion can affect the transport of others
  • PAH and penicillin (good)
  • some other drug interactions can be fatal
45
Q

Why is low dose penicillin coupled with PAH good

A

Competing for transporters

46
Q

Where does PCT secrete organic cations

A

Into the tubular fluid

  • creatinine, dopamine, epi/NE
  • morphine, atropine, etc

Trades for H+

47
Q

Transport maximum

A

Any transport process that utilizes a transport protein can become saturated

48
Q

What can cause transporter maximum

A

Too much solute, not enough transporters

49
Q

What is the Tm of the PCT

A

325mg/min

Excretion=FL-Tm

50
Q

Where does renal threshold occur

A

As you are approaching the maximum

  • some glucose gets missed as you approach Tm
  • play area is where the lines are not linear
51
Q

If plasma glucose is 400mg/dl and GFR is 125ml/min. How much glucose is secreted. Tm for glucose is 325mg/min

A

Excretion=FL-Tm
FL=XaGFR
FL=4mg/ml125=5001

500-325=175mg/min

52
Q

What can be used as a readout of kidney health

A

Tm

53
Q

What is the thin descending loop of henle permeabel to

A

Only water

54
Q

Where does the DTL passes through

A

Hyperosmotic interstitium (300-1200mOsm)

55
Q

How is water reabsorbed in the DTL

A

Due to osmotic forces

  • volume of tubular fluid decreases
  • solutes remain
  • osmolarity increases
56
Q

What is another name for the DTL

A

Tue concentrating segment

57
Q

The ATL and water

A

It is impermeable to water, no water movement and no volume change

58
Q

What is reabsorbed in the ATL

A

Some solutes passively, due to slight electrical forces

59
Q

Transport in the ATL

A

Lost of transport

-active, passive, paracellular, and transcellular

60
Q

What is another name for the ATL

A

The diluting segment

61
Q

What helps generate hyperosmotic gradient in tissue

A

ATL

62
Q

Where is the Na-Cl-K symporter found

A

ATL

63
Q

What does Lasix block

A

The Na-Cl-K symporter in the ATL

64
Q

How does the macula densa sense Na+ to adjust GFR

A

Na-Cl-K symporter in the ATL

65
Q

K+ transport is _______ in response to voltage difference in the ATL at the Na-Cl-K symporter

A

Paracellular

-along with other positively charged ions

66
Q

Where is the site of the macula densa and juxtaglomerular apparatus

A

ATL

  • between the ascending loop and the distal tubule
  • sense tubular sodium load by measuring transport rate, adjusts GFR accordingly
67
Q

What does the early distal tubule do

A

Keep dilating tubular fluid
IMPERMEABLE TO WATER
-lots of transport )active, passive, para and trans)

68
Q

Where is the Na-Cl symporter located

A

Early distal tube

69
Q

What do thiazides block

A

Na-Cl symporter in the early distal tubule

70
Q

Other than the Na-Cl sympoter, what else is found in the early distal tubules?

A

Some Na-Cl-K symporters, not a ton

71
Q

Late distal and cortical collecting duct and water

A

Variable permeable to water

  • responds to ADH
  • tubular fluid is negative due to ammonium secretion
72
Q

Where is the tubular fluid negative due to ammonium secretion

A

Late distal and cortical collecting ducts

73
Q

What responds to ADH

A

Late distal and cortical collecting duct

74
Q

What does the late distal and cortical collecting duct reabsorb?

A

NaCl and some water isoosmotically

75
Q

What does the late distal and cortical collecting duct secrete?

A

K= and acid or bicarbonate if needed

76
Q

What is the major site of aldosterone function

A

Late distal and cortical collecting duct

77
Q

What are the two kinds of cells in the late distal and cortical collecting duct

A

Principle cells and intercalated cells

78
Q

What are the principle cells of the late distal and cortical collecting duct important for

A

In the regulation of Na+, Cl-, K+, and water

  • lots of active transport
  • apical Na+ and K+ channels are present
  • Cl- follows Na+
79
Q

What is very sensitive to Na levels in the principle cells of the late distal and cortical collecting duct

A

Na-K pump

80
Q

What does aldosterone do the principle cells of the late distal and cortical collecting duct

A

Increases Na-K pump activity

  • also opens more apical Na+ channels
  • lose K+ to save Na+ and water
81
Q

What blocks aldosterone from binding the principle cells of the late distal and cortical collecting duct

A

Spironolactone

82
Q

What do the intercalated cells of the late distal and cortical collecting duct do

A
  • regulate H+ and HCO3- secretion/reabsorption
  • can affect K_ levels (moves opposite H+)
  • cellular function is dependent on presence of H+ in cells
  • must have carbonic anhydrase function
83
Q

What do acidotic tubular cells in the late distal and cortical collecting duct do

A

Pump acid into the urine, bicarbonate into the blood

84
Q

What are the types of intercalated cells in the late distal and cortical collecting duct

A

Acidotic and alkolotic

85
Q

What do alkalotic cells in the distal and cortical collecting ducts do

A

Put acid back in blood, pump base (HCO3-) into urine

86
Q

What secretes acid to correct acidosis

A

Intercalated type A cells (acidotic cells)

87
Q

What secretes base to correct alkalosis?

A

Intercalated type B cells (Alkalotic cells)

88
Q

What is the final and more critical site of water balance in urine

A

Medullary collecting ducts

89
Q

Medullary collecting ducts response to ADH

A
  • ADH binds V2 receptors (vospressin 2)
  • ADH adds aquaporins 2 (AQP2) to the apical membrane
  • allows water to LEAVE tubule in response to osmotic gradient established by loop of henle of juxtamedullary nephrons
  • makes concentrated urine
90
Q

If there are no ADH in the medullary collecting ducts

A

They are impermeable to water, make dilute urine

91
Q

PCT reabsorops ____ of Na and H2O

A

65%

-all metabolic substances reabsorbs

92
Q

DTL reabsorbs

A

20% H2O

93
Q

TLA reabsorbs

A

25% Na

-lots of Cl-, K+, Ca2+, bicarbonate, Mg2+ as well

94
Q

Early DTL reabsorbs

A

5% Na_

95
Q

Late DTL and CD reabsorbs

A

Less than 10% of Na+ and H2P

-variable with ADH

Physiology Block 7 (10 decks)

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