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Renal > Quiz 2 > Flashcards

Quiz 2 Flashcards

0
Q

Two ways substances can be transported?

A

Tubular reabsorption: Lumen–>peritubular capillary

Tubular secretion: Peritubular capillary–>lumen

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1
Q

Amount excreted equation

A

(amount filtered) - amount reabsorbed(+ amount secreted)

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2
Q

What is Transcellular transport across the renal epithelial cells?

A

Transport through the cell across TWO membranes (luminal and basolateral

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3
Q

What is Paracellular transport across the renal epithelial cells?

A

Transport b/w cells (across tight junctions by simple diffusion)

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4
Q

Most renal tubular transport occurs via what route?

A

the transcellular route

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5
Q

Three types of trans-membrane transport systems

A

1) channel-mediated diffusion
2) carrier-mediated diffusion
3) carrier mediated “active transport”

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6
Q

Channel-mediated diffusion requires what?

A

Electrochemical gradient since its “passive”

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7
Q

Carrier-mediated diffusion has what types of transport?

A

Uniport, symport, antiport

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8
Q

Carrier-mediated “active transport” needs what?

A

energy to transport against the electrochemical gradient

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9
Q

Where is there absolute dependence on Na+/K+ ATPase?

A

ONLY on the basolateral membrane to maintain LOW intracellular Na+ concentration

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10
Q

In the Cortical Collecting Tubule, Na+ enters the cell via…

A

luminal membrane Na+ selective channels

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11
Q

The proximal tubule has what type of transporter?

A

luminal membrane Na+ glucose co-transporter

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12
Q

In the proximal tubule, the “downhill” movement of Na+ across the luminal membrane into the cell facilitates what?

A

The “uphill” movement of glucose

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13
Q

What does the glucose uniporter transport do?

A

transports glucose out of the cell across the basolateral membrane

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14
Q

Two co-transporters for glucose? What is their capacity and affinity for each?

A

SGLT-2: high capacity-low affinity

SGLT-1: low capacity-high affinity

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15
Q

What type of inhibitors are used for type-2 diabetics?

A

SGLT-2 inhibitors

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16
Q

How are proteins absorbed?

A

Receptor mediated endocytosis

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17
Q

Endocytised proteins are degraded to what? And how are they released?

A

amino acids

basolaterally

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18
Q

Approximately how much of the glomerular filtrate is reabsorbed in the proximal tubule?

A

2/3

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19
Q

Many solutes are completely absorbed proximally except what?

A

Cl- which is reabsorbed (passively) in the later proximal tubule

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20
Q

In the proximal tubule, what is the net fluid movement?

A

Isosmotic fluid reabsorption b/c 2/3 of filtered water and 2/3 of the filtered solute is reabsorbed

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21
Q

In the proximal tubule, complete reabsorption of the isotonic fluid is a two-step process. What are the two steps?

A

1) Movement from lumen–>interstitium

2) Movement from interstitium–>peritubular capillaries

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22
Q

What promotes peritubular capillary (PC) fluid uptake?

A

Low Ppc (downstream of afferent / efferent resistance points)

High PIEpc (filtration creates high PC plasma protein concentration

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23
Q

The proximal tubule reabsorbs a CONSTANT percentage of the filtered load. What is this percentage?
What is this called?

A

~67%

Glomerulotubular (GT) balance

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24
Q

Glomerulotubular (GT) balance helps to do what?

A

maintain a relatively constant delivery of fluid to the distal nephron

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25
Q

What cant be assessed using In Vivo Micropuncture to analyze renal tubular function? Why?

A

Cant assess collecting tubule function by micropunction, or transport in the juxtamedullary nephrons

B/c neither are accessible from the surface of the kidney

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26
Q

Transport capacity of essentially any sub-segment of the nephron can be assessed by what method?

A

microperfusion

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27
Q

What does “Splay” represent?

A

The slight variance in Tm b/w individual nephrons

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28
Q

Where is the primary site of secretion for organic anions and cations?

A

proximal tubule

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29
Q

Cortical / juxtamedullary nephron ratio correlates with what?

A

the capacity to concentrate urine

increase percent juxtamedullary = increase concentrating ability

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30
Q

Transport characteristics of the thin descending limb of Henle’s loop?

A

Reabsorbs H20

Does NOT reabsorb NaCl (or other solutes)

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31
Q

In the thin descending limb (TDL) of henle’s loop, tubular fluid osmolarity __increases or decreases__ as it flows toward the papilla. This is due to what?

A

increases

water reabsorption

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32
Q

TDL system is capable of reabsorbing how much H2O/day?

A

~30-40 L H2O/day

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33
Q

Characteristics of the ascending limb of Henle’s loop?

A

Avidly reabsorbs NaCl

Does NOT reabsorb H2O

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34
Q

In the ascending limb of Henle’s loop, what percent of the filtered load of NaCl gets reabsorbed?

A

20-25%

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35
Q

The ascending limb of Henle’s loop generates what type of tubular fluid? Whats the nickname for this segment?

A

hypotonic

its considered the “diluting segment” of the nephron

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36
Q

The thick ascending limb of Henle’s look is dependent on what? Where are they located?

A

Na+-K+-ATPase located on the basolateral membrane

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37
Q

In the thick ascending limb, the reflux of K+ entering into the tubular lumen via a selective channel generates what type of potential? This provides the driving force for what?

A

lumen-positive

paracellular transport of multiple cations (Na+,K+,Ca2+,Mg2+)
AND
ensures adequate supply of cotransporters

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38
Q

What are furosemide and bumetanide?

A

Drugs that inhibit Na+-K+-2Cl- cotransporters in the thick ascending limb

They are “loop diuretics” (allow salt to be passed and excreted in the urine)…prescribed for hypertension, edema, etc.

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39
Q

What occurs as a result of adrenal insufficiency?

A

decrease urine diluting and concentrating ability

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40
Q

Transport in the thick ascending limb (TAL) is increased by what?

A

antidiuretic hormone
insulin
glucagon
isoproterenol

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41
Q

Transport in the thick ascending limb (TAL) is inhibited by what?

A

atrial natriuretic peptide
adenosine
dopamine
bradykinin

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42
Q

Distal nephron consists of…

A 
distal convoluted tubule
collecting tubule (cortical-->papillary)
43
Q

In the distal nephron, distal delivery is __% of the filtered load of H2O and ___% of the filtered load of NaCl (and KCl)

A

both 10%

44
Q

What regulates distal nephron transport of H2O?

A

Antidiuretic hormone (ADH)

45
Q

Distal nephron transport of NaCl is regulated by what?

A

Aldosterone

46
Q

What does ADH do to the collecting tubule?

A

makes it permeable to water which promotes water reabsorption and generates a smaller volume of concentrated (hypertonic) urine

i.e ANTIDIURESIS

47
Q

In the absence of ADH, is the collecting tubule permeable to water?

A

NO

48
Q

Reabsorption of water by the collecting tubule system is dependent on the presence of what in the luminal membrane?

A

water channels called aquaporins

49
Q

ADH stimulates insertion of what?

A

pre-existing AQP-2 channels into the luminal membrane

50
Q

Increase in cyclic AMP ultimately results in what?

A

increase water permeability

51
Q

AQP-3 channels are constitutively expressed in the _____

A

basolateral membrane

52
Q

What explains the water impermeability of the ascending limb?

A

lack of luminal aquaporins

53
Q

Whats being reabsorbed and whats being secreted in the cortical collecting tubule?

A

Na+ is reabsorbed

K+ secreted

54
Q

How does aldosterone control reabsorption?

A

Increase number of luminal membrane Na+ channels

Increase sodium-potassium-ATPase (de novo synthesis of pumps)

Increase Krebs cycle enzyme synthesis
(thus more ATP)->increaseATPase activity

55
Q

Aldosterone and cortisol have similar affinity for what type of receptor?

A

mineralocorticoid

56
Q

Parathyroid Hormone (PTH) stimulates what?

A

Increases Ca2+ reabsorption in the DISTAL TUBULE

57
Q

Plasma ADH levels control ____ and ____

A

medullary interstitial urea
medullary osmolarity

Decrease in ADH->decrease urea reabsorption->decrease med.int.urea–> decrease med. osmolarity

58
Q

If ADH levels increase, what happens to medullary osmolarity?

A

increases

59
Q

Medullary blood supply is essential for what?

A

Nutrient supply

Removal of reabsorbed H2O and NaCl

60
Q

Countercurrent exchange in the vasa recta capillaries preserves what?

A

The hypertonic gradient in the medullary interstitium

61
Q

In the countercurrent exchange, plasma flowing out of the medulla has a higher or lower osmolality than that entering?
What about exiting plasma flow rate?

A

higher

higher

62
Q

Important function of the vasa recta?

A

remove ALL water reabsorbed by the descending limbs and medullary collecting tubules, and MOST of the NaCl reabsorbed by the ascending limb

63
Q

What is the only output that can be precisely controlled?

A

urine output

64
Q

Maximum DIURESIS

Urine Volume:?
Urine Osmolality:?

A

20-25 L/day

50-75 mOsm/kg

65
Q

Maximum ANTIDIURESIS

Urine Volume:?
Urine Osmolality:?

A

0.5 L/day

1200-1400 mOsm/kg

66
Q

Where is ADH synthesized?

A

In the neural cell bodies located in the supraoptic and paraventricular nucleii of the hypothalamus

67
Q

Where is ADH stored?

A

In nerve terminals in the posterior pituitary

68
Q

ADH is regulated by what receptors?

A

hypothalamic osmoreceptors

volume receptors

69
Q

Which receptors are more sensitive for ADH secretion:
Osmoreceptor system or baroreceptor system?
What does this mean?

A

osmoreceptor system

Small changes in plasma osmolality can elicit large changes in ADH secretion

70
Q

Small changes in ADH can elicit large changes in _____

A

urine osmolality

increase osmolality–> decrease in urine VOLUME

71
Q

Causes of Syndrome of Inappropriate ADH secretion (SIADH)?

A

head trauma, encephalitis, meningitis
ADH secreting tumors (lung, pancreas)
Drug-induced (nicotine, morphine, chemotherapeutic agents)

72
Q

Effects of Syndrome of Inappropriate ADH secretion (SIADH)?

A

increase ADH->increase H2O reabsorption-> HYPONATREMIA

decrease serum Na->dec. plasm osm->inflush of H2O into brain cells—>leads to coma

73
Q

Causes of Diabetes Insipidus (D.I.)

A

HYPOTHALAMIC (CENTRAL) D.I. (dec. production or release of ADH)

NEPHROGENIC D.I. (renal unresponsiveness to ADH)

74
Q

Effect of Diabetes Insipidus (D.I.)

A

dec. ADH->dec. H2O->HYPERNATREMIA

inc. serum Na–>inc. plasma osm–>efflux of H2O (out of brain cells)——->Coma

75
Q

What does free water clearance provide?

A

a non-invasive assessment of diluting efficiency of the thick ascending limb

76
Q

Kidneys maintain constant ECF volume by adjusting what?

A

NaCl excretion to match NaCl intake

77
Q

What percent of filtered load of sodium is excreted?

A

less than 1%

78
Q

Aldosterone regulates the excretion of what percent of the filtered load of sodium?

A

5%

79
Q

Total body Na+ changes are sensed as changes in what?

A

Effective Circulating Volume (ECV)

80
Q

Extra cellular volume is monitored by what?

A

Baroreceptors

81
Q

What is the rate-limiting step in aldosterone release from adrenal cortex?

A

renin (enzyme) release by kidney

82
Q

Where is renin secreted within the kidneys?

A

granular cells of the afferent arterioles

82
Q

What does angiotensin II do in its rapid-onset effects in response to decreased blood pressure (e.g. hemorrhage)?

What are its longer-onset effects?

A

Helps restore “normal” b.p. despite low ECV (inc. TPR and inc. CO)

Restore normal ECV (dec. NaCl and H2O excretion and increase NaCl and H2O intake)

83
Q

Sustained increase in aldosterone secretion results in what?

A

relatively transient Na+ retention

84
Q

A 15-25mm Hg increase in b.p. results in what?

A

pressure natriuresis and pressure diuresis= Aldosterone Escape

85
Q

Describe how long renal adjustments for changes in H2O take and how long renal adjustments for NaCl intake take?

A

H2O intake are rapid (minutes)

Can take several days

86
Q

Increased ECF causes what?

A

Increase in ATRIAL NATRIURETIC PEPTIDE (ANP)

87
Q

What secretes atrial natriuretic peptide (ANP)?

A

atrial myocytes

88
Q

What does ANP do?

A

Increase NaCl and H2O excretion to decrease b.p.

89
Q

How does ANP increase NaCL and H2O excretion?

A

Vasodilation of afferent arteriole–>increase GFR
inhibit aldosterone secretion
inhibit NaCl reabsorption in proximal tubule and collecting tubule
Antagonized ADH action

90
Q

What is the gene family that express Na+-K+-Cl- cotransporter along the nephron ?

A

Electro Neutral sodium Chloride Co-transporter (ENCC2)

91
Q

Bartter’s Syndrome

A

Mutations in ENCC2 and/or luminal K+ (ROMK) channel in the THICK ascending limb

92
Q

What part of the nephron does bartter’s syndrome effect?

A

THICK ascending limb

93
Q

Physiological impact of bartter’s syndrome?

A

Decrease NaCl reabsorption (inc. NaCl excretion)
Volume depletion b/c water loss
Hyperreninemic hyperaldosteronism
Hypercalciuria (dec. lumen ive potential)
Hypokalemic metabolic alkalosis

94
Q

How many are affected by Polycystic Kidney Disease (PKD) in the U.S?

A

600,000

95
Q

Polycystic Kidney Disease (PKD)

A

Cysts (fluid filled sacs) that develop from renal tubular epithelial cells
Most cases autosomal dominant (ADPKD) (85%)

96
Q

What is Autosomal Dominant Polycystic Kidney Disease (ADPKD) often associated with?

A

hypertension

97
Q

ADPKD can lead to what in 50% of patients?

A

end-stage renal disease

98
Q

Diuretic drugs ultimately do what?

A

increase NaCL water excretion

99
Q

How are diuretics classified?

A

According to site and mechanism of action

100
Q

What is Proximal tubule carbonic anhydrase inhibitors?

e.g. acetazolamide

A

A diuretic drug that targets this specific enzyme to

inhibit Na+HCO3- “reabsorption”

100
Q

What are Collecting tubule “K+-sparing” diuretics?

e.g. amiloride

A

A diuretic drug that specifically inhibits luminal Na+ channels

101
Q

What are thick ascending limb “loop diuretics”

(e.g.furesemide, bumetanide)?

A

Diuretic drug that specifically targets this transport protein and
inhibits Na+-K+-2Cl- transport

102
Q

What are collecting tubule “K+-sparing” diuretics?

e.g. spironolactone

A

Diuretic drug that targets hormone receptors acting as an aldosterone receptor antagonist

103
Q

What are Distal Tubule Luminal Na+-Cl- cotransport inhibitors?
(e.g. thiazides)

A

Diuretic drug that inhibits this cotransport inhibitor

104
Q

what does an increase in osmolality do to urine volume?

A

decreases urine volume (piss less)

Renal (3 decks)

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