Brs Renal Physiology Set

Front 1

The 60-40-20 rule is?

Back 1

Body Weight x
60% is total body water
40% is intracellular fluid
20% is extracellular fluid

Front 2

what happens to osmolarity of ECF if person is infused with isotonic saline solution?

Back 2

stays the same

Front 3

Describe the isotonic water transport at the proximal tubule.

Back 3

- high Lp
- only need small osmotic gradient: Na+ uptake leads to slight decrease in hypo-osmolarity of luminal fluid.
- fluid uptake by peritubular capillaries driven by Starling forces

Front 4

Markers used to measure TBW?

Back 4

tritiated water
D20
antipyrene

Front 5

Clearance equation

Back 5

C = (urinary conc x urinary flow) / plasma conc

Front 6

Why is Na+ delivery to distal tuble more or less constant?

Back 6

- tubuloglomerular feedback mechanism:
constriction of afferent arteriole in response
to high tubular [Na+] sensed by macula densa.

- glomerulotubular balance:
ability of proximal tubule to absorb
more Na+ when GFR is increased

Front 7

What are the three hormones that the kidneys synthesize and secrete?

Back 7

Renin
Erythropoietin
1,25-dihydroxycholecalciferol

Front 8

What happens to the following with isotonic NaCl infusion?

- ECF volume
- ICF volume
- ECF osmolarity
- Hct
- serum [Na+]

Back 8

- ECF volume: up
- ICF volume: no change
- ECF osmolarity: no change
- Hct: down
- serum [Na+]: no change

Because osmolarity is unchanged, there is no water shift between ECF and ICF.

Front 9

major cations/anions of ICF?

Back 9

cations--K+, Mg2+; anions--protein, organic phosphates (eg ATP)

Front 10

Total body water (TBW) is highest in?

Back 10

____ is highest in newborns and adult males.

Front 11

what happens to osmolarity of ECF if person has loss of isotonic fluid? (example)

Back 11

diarrhea
stays the same

Front 12

Where is glucose absorbed in the nephron?

Back 12

proximal tubule (100%)
- early part: apical SGLT2 (Na+/Glu) and basalateral GLUT transporter
- late part: apical SGLT1 and SGLT2 (Na+/Glu) and basalateral GLUT transporter.
- Tmax = 1.9mMol/min

Front 13

Markers used to measure ECF?

Back 13

sulfate
inulin
mannitol

Front 14

How much of the CO is the RBF?

Back 14

20%

Front 15

What % of Na+ is excreted with max aldolsterone?

Back 15

0.1%

Front 16

What is the difference between superficial cortical nephrons and juxtamedullary nephrons?

Back 16

The two types of nephrons are distinguished by the location of their glomeruli.

The superficial cortical nephrons
have their glomeruli in the outer cortex, have relatively short loops of Henle, and descend only into the outer medulla. Juxtamedullary nephrons have their glomeruli near the corticomedullary border.


The glomeruli
are also larger, have higher glomerular filtration rates, have longer loops of Henle that descend deep into the inner medulla and papilla, and are essential for the concentration of urine.

The vasa recta are found following the juxtamedullary nephrons.

Front 17

What happens to the following with diarrhea (isotonic volume loss)?

- ECF volume
- ICF volume
- ECF osmolarity
- Hct
- serum [Na+]

Back 17

- ECF volume: down
- ICF volume: no change
- ECF osmolarity: no change
- Hct: up
- serum [Na+]: unchanged

BP decreases because ECF volume decreases.

Front 18

markers for measuring TBW

Back 18

D2O, tritiated H2O

Front 19

markers for measuring ECF?

Back 19

mannitol, sulfate, inulin

Front 20

Major intracellular fluid (ICF) cations are?

Back 20

__________________ cations are K+ and Mg2+.

Front 21

what happens to osmolarity of ECF if person has high NaCl intake?

Back 21

incresaes

Front 22

What is the Tm and threshold for plasma [glucose]?

What explains the splay?

Back 22

- Tm = 350 mg/dl
- threshold = 250 mg/dl
- difference is called splay which is explained by heterogeneity of nephrons and the relatively low affinity of the Na/Glu transporter.

Front 23

markers used to measure plasma?

Back 23

RISA
evan's blue

Front 24

What are some things that vasodilate the renal arterioles?

Back 24

PGE2
PGI2
Bradykinin
NO
Dopamine

Front 25

What % of Na+ is excreted with no aldolsterone?

Back 25

5%

Front 26

What does the renal artery branch into?

Back 26

Interlobar arteries
Arcuate arteries
Cortical radial arteries

Front 27

What happens to the following with high NaCl intake?

- ECF volume
- ICF volume
- ECF osmolarity
- Hct
- serum [Na+]

Back 27

Hyperosmotic volume expansion
- ECF volume: up
- ICF volume: down
- ECF osmolarity: up
- Hct: down
- serum [Na+]: up

Water shifts from ICF to ECF because of increased ECF osmolarity.

Front 28

markers for measuring plasma?

Back 28

RISA, Evan's blue

Front 29

Major intracellular fluid (ICF) anions are?

Back 29

___________________ anions are protein, and organic phosphates (ATP, ADP, AMP).

Front 30

what happens to ECF osmolarity if person is sweating in the desert?

Back 30

increases (sweat is hyposmotic... more water than salt is lost)

Front 31

What type of diabetes is this?

- glucosuria
- normal plasma [glucose]
- diuresis
- thirst

Back 31

renal diabetes mellitus
- reduced Tmax, reduced threshold, increased splay

Front 32

measuring interstitial fluid?

Back 32

ISF = ECF - plasma

Front 33

Over what range of arterial pressures does autoregulation occur?

Back 33

80-200 mmHg

Front 34

Where is the receptor for aldolsterone located?

Back 34

on the nucleus of principal cells and type A intercalated cells

Front 35

Who has the highest percentage of water? Who has the lowest percentage of water?

Back 35

Thin men have the highest percentage of body weight as water (~70%).
Obese women have the lowest percentage of body weight as water (~50%).

Front 36

What happens to the following when sweat or with fever or diabetes insipidus?

- ECF volume
- ICF volume
- ECF osmolarity
- Hct
- serum [Na+]

Back 36

Hyperosmotic volume contraction
- ECF volume: down
- ICF volume: down
- ECF osmolarity: up
- Hct: no change
- serum [Na+]: up

Because RBC shrink due to high plasma osmolarity, it offsets the volume loss so Hct stays the same.

Front 37

markers for measuring interstitial fluid?

Back 37

indirect: ECF - plasma (mannitol - Evan's blue)

Front 38

Major ECF cation is?

Back 38

__________ cation is Na+.

Front 39

what happens to ECF osmolarity in SIADH?

Back 39

decreases

Front 40

Where is PAH absorbed/secreted?

Back 40

- PAH is secreted in the proximal tubule
- at low [PAH], secretion rate increases
- at high [PAH] above Tmax, scretion rate is constant

Front 41

measuring ICF

Back 41

ICF = TBW - ECF

Front 42

What are the mechanisms for autoregulation of RBF?

Back 42

Myogenic mechanism: afferent arteriole constricts in response to stretch
TGF mechanism: increased flow across the macula densa constricts the afferent arteriole

Front 43

Mechanism of aldolsterone.

Back 43

bind to receptors on nuclear membrane of principal cell and type A intercalated cells.
- stimulate Na+/K+ channels on principal cells
- stimulate H+/K+ channels on type A intercalated cells
- increase oxidative metabolism of taget cells

Front 44

How much water is in the ICF? In the ECF?

Back 44

About two-thirds of total body water is in the ICF. About one-third is in the ECF.

Front 45

What happens to the following with SIADH (excess ADH)?

- ECF volume
- ICF volume
- ECF osmolarity
- Hct
- serum [Na+]

Back 45

Hyposmotic volume expansion
- ECF volume: up
- ICF volume: up
- ECF osmolarity: down
- Hct: no change
- serum [Na+]: down

Hct is expected to decrease, but remains unchanged because water shifts into RBC, increasing their volume and offsetting the diluting effect.

Front 46

markers for measuring ICF?

Back 46

do indirectly: TBW - ECF (D2O - mannitol)

Front 47

Major ECF anions are?

Back 47

_________ anions are Cl- and HCO3-.

Front 48

what happens to ECF osmolarity in adrenocortical insufficiency (NaCl loss)?

Back 48

decreases (lack of aldosterone), kidneys excrete more NaCl than water

Front 49

PAH can be used to measure the size of which fluid compartment?

Back 49

RPF

Front 50

Volume of body compartment calculation

Back 50

Volume = Amt injected - Amt excreted / concentration

Front 51

What substance is used to calculate RPF?

Back 51

PAH, because it is filtered and secreted

Front 52

What some stimulators of aldolsterone?

Back 52

- high plasma [K+]
- angiotensin II

Front 53

What is the 60-40-20 rule?

Back 53

60% of body weight is water, 40% is ICF, 20% is ECF.

Front 54

What happens to the following with adrenal insufficiency (less aldolsterone)?

- ECF volume
- ICF volume
- ECF osmolarity
- Hct
- serum [Na+]

Back 54

Hyposmotic volume contraction - loss of NaCl
- ECF volume: down
- ICF volume: up
- ECF osmolarity: down
- Hct: up
- serum [Na+]: down

BP decreases because of the decrease in ECF volume.

Front 55

What happens if isotonic NaCl is infused?

Back 55

isosmotic volume expansion

Front 56

The dilution method to measure TBW uses?

Back 56

__________ is measured with tritiated water, or D20.

Front 57

what happens to plasma protein [] and hematocrit in infusion of isotonic NaCl?

Back 57

decreases (overall increase in fluid)

Front 58

How to calculate the fraction of H2O reabsorbed using inulin method?

Back 58

1 - 1/(U/P)inulin

Front 59

infusion of isotonic NaCl

aka. iso-osmotic volume expansion

Back 59

- ECF volume increases
- no change in osmolarity
- no change in ICF volume
- plasma protein/ Hct decrease
- arterial BP increases

Front 60

How close is calculated RPF to actual RPF?

Back 60

It underestimates actual RPF by 10%

Front 61

Where is aldolsterone produced?

Back 61

produced and released by zona glomerulosa cells of adrenal cortex.

Front 62

How much of the ECF water is found in the interstitial fluid? In the plasma?

Back 62

About three-fourths of the ECF is found in the interstitial compartment, and the remaining one-fourth is found in the plasma.

Front 63

What is this fluid compartment?

- volume: 3.5L
- [Na+] = 146 mM
- [Cl-] = 105mM
- [K+] = 4.2 mM
- osmolarity = 285

Back 63

Plasma
- can be measured by Evan's Blue

Front 64

What happens to fluid volumes if you have diarrhea?

Back 64

loss of isotonic fluid-->isometric volume contraction

Front 65

The dilution method to measure ECF uses?

Back 65

__________ is measured with mannitol, inulin, or sulfate.

Front 66

what happens to plasma protein [] and hct in diarrhea?

Back 66

increases (from volume contraction)

Front 67

What % filtered K+ remains in the tubular fluid given that U/P(K+) / U/P (inulin) is 0.3?

Back 67

30%

Front 68

diarrhea

aka. isoosmotic volume contraction

Back 68

- ECF volume decreases
- no change in osmolarity
- no change in ICF volume
- plasma protein/Hct increase
- arterial BP decreases

Front 69

What is the formula for RBF?

Back 69

RBF = RPF / (1-hematocrit)

Front 70

Size of ECF volume is determined by ___.

A. Na+
B. HCO3-
C. Glucose
D. K+

Back 70

A.

Front 71

How much of the blood is plasma?

Back 71

On a volume basis, plasma constitutes 55% of blood volume, and blood cells constitute the remaining 45% of blood volume.

Front 72

What is this fluid compartment?

- volume: 10.5L
- [Na+] = 142 mM
- [Cl-] = 107mM
- [K+] = 4 mM
- osmolarity = 283

Back 72

ISF
- ECF - P

Front 73

what happens to fluid volumes if excessive NaCl intake?

Back 73

hyperosmotic vol expansion

Front 74

The dilution method to measure plasma volume uses?

Back 74

____________ is measured with Evans blue, or radiolabled albumin (RISA).

Front 75

what happens to plasma protein [] and hct in high NaCl consumption?

Back 75

decrease (ICF shrinks to accomodate the increased osmolarity in ECF, this dilutes out the plasma protein)

Front 76

Where are Na+ reabsorbed? by what transporters?

Back 76

1) 67% at proximal tubule

- Na+/glu cotransporter
- Na+/H+ exchanger
- Na+/HCO3- cotransporter
- Na+/AA cotransporter
- Na+/phosphate cotransporter
- Na+/lactate cotransporter
- Na+/Cl- cotransporter in late proximal tubule

2) 25% at thick ascending limb of loops of Henle:

- Na+/K+/2Cl- transporter

3) 8% at distal tubule and collecting duct

- early distal tubule: Na+/Cl- transporter
- late distal tuble and collecting duct: Na+/K+ channels which are stimulated by aldolsterone

Front 77

excessive NaCl intake

aka. hyperosmotic volume expansion

Back 77

- ECF osmolarity increases
- volume shifts from ICF to ECF
- ECF volume increases
- ICF volume decreases
- plasma protein/Hct decrease

Front 78

What substances are used to calculate GFR?

Back 78

Inulin or creatinine, because they are filtered but are not secreted or reabsorbed

Front 79

Factors that regulate Na+ balance.

Back 79

1) renin-angiotensin-aldolsterone system:
- low ECF -> renin released from JG cells -> Ang converted to AngI -> AngI converted to AngII(vasoconstriction) by ACE in the lungs -> aldolsterone release -> increased Na+ reabsorption -> normal ECF restored
2) GFR regulation: high ECF -> increased GFR and decreased proximal fluid resorption
3) third factor
- increased venous filling pressure -> ANP release -> decreased sympathetic tone -> decrease Na+ reabsorption
- ourabain-like factor (hypothalamus/adrenal cortex) -> inhibit Na+/K+ pumps of collecting duct

Front 80

What is the average hematocrit? Is it higher in males or in females?

Back 80

The average hematocrit is 0.45 or 45%. It is higher in males (0.48) than in females (0.42).

Front 81

What is this fluid compartment?

- volume: 28L
- 40% body weight
- [Na+] = 10 mM
- [Cl-] = 6mM
- [K+] = 160 mM
- osmolarity = 283

Back 81

ICF
- TBF - ECF

Front 82

what happens to fluid volumes if you get lost in a desert? (dehydration)

Back 82

hyperosmotic vol contractino

Front 83

The TBW of a 70 kg man is?

Back 83

The TBW of a ___ man is 42 L.

Front 84

what happens to plasma protein [] and hct when swaeting in desert?

Back 84

protein increases
hct stays same b/c fluid leaves rbcs to offset fuid loss

Front 85

What is the action of ouabain?

Back 85

block Na+/K+ ATPase that set up the diffusion gradient

Front 86

sweating in a desert - loss of water

aka. hyperosmotic volume contraction

Back 86

- ECF osmolarity increases
- water shifts from ICF to ECF until osmolarity has equilibriated
- ICF volume increases
- plasma protein conc. increases
- Hct remains the same

Front 87

What happens to the BUN/creatinine ratio during azotemia (hypovolemia)?

Back 87

It increases (greater than 20:1)

Front 88

What happens when kidney is unable to maintain normal ECF as in severe blood loss and excessive sweating?

Back 88

>15% volume contraction -> creaving for Na+ -> ingestion of salt -> Na+ balance

Front 89

What is the Gibbs-Donnan effect?

Back 89

The Gibbs-Donnan effect predicts that plasma will have a slightly higher concentration of small cations than interstitial fluid and a slightly lower concentration of small anions.

Front 90

What is this fluid compartment?

- volume: 14L
- 20% body weight
- [Na+] = 144 mM
- [Cl-] = 106mM
- [K+] = 4.3 mM
- osmolarity = 284

Back 90

ECF
- can be measured by inulin

Front 91

what happens to fluid volumes in SIADH?

Back 91

hyposmotic volume expansion

Front 92

How are ECF, ICF, ECF osm, Hct, and [Na+] affected by:
isoosmotic volume expansion?

Back 92

ECF increases
ICF unchanged
ECF osm unchanged
Hct decreases
[Na+] unchanged

Front 93

what happens to plasma protein [ ] and hct in siadh

Back 93

decreases
stays same

Front 94

What is the action of phlorizin?

Back 94

Block SGLT2 (Na+/Glu) in proximal tubule

Front 95

syndrome of inappropriate ADH

aka. hypoosomotic volume expansion

Back 95

- water retention = decreased ECF osmolarity, increased ECF volume
- water shifts from ECF to ICF --> ICF volume increases, osmolarity decreases
- plasma protein decreases
- hct unchanged

Front 96

What happens to GFR as we age?

Back 96

Decreases

Front 97

How does kidney react to volume depletion?

Back 97

volume depletion -> increase AngII and aldolsterone, release of NE -> increase in Na+ reabsorption -> increased osmolarity -> ADH release -> water reabsorption -> volume returns to normal

Front 98

What is special about mannitol? Where is it distributed?

Back 98

Mannitol is a large molecular weight sugar that cannot cross cell membranes. It will be distributed in ECF but not ICF.
Mannitol is a marker for ECF volume.

Front 99

What is this fluid compartment?

- volume: 42L
- 60% body weight

Back 99

TBF
- can be measured by D2O, THO, antipyrine

Front 100

what happens to fluid volumes if adrenocortical insufficiency?

Back 100

hyposmotic volume contraction

Front 101

How are ECF, ICF, ECF osm, Hct, and [Na+] affected by:
isoosmotic volume contraction?

Back 101

ECF decrease
ICF no change
ECF osm no change
Hct increase
[Na+] no change

Front 102

what happens to plasma protein [] and hct in adrenal insuff?

Back 102

plasma protein increases
hct increases (from decreased ECF volume and rbc swelling from water entry)

Front 103

What is the action of acetazolamide?

Back 103

carbonic anhydrase inhibitor
- diuretics that act in proximal tubule by inhibiting reabsorption of HCO3-.

Front 104

adrenocortical insufficiency - loss of NaCl

aka. hypoosmotic volume contraction

Back 104

- osmolarity of ECF decreases
- volume of ECF decreases, shifts to ICF
-ICF osmolarity decreases, volume increases
- plasma protein conc. increases
- Hct increases

Front 105

What is the equation for filtration fraction?

Back 105

FF = GFR / RPF

Front 106

What is the strongest stimulator of aldolsterone release?

Back 106

high [K+] > 5mM

Front 107

What substances are distributed wherever water is found?

Back 107

The markers for total body water include isotopic water (D2O and tritiated water) and antipyrine.

Front 108

Why is [Na+] higher in plasma than in ISF, but [Cl-] lower in plasma than ISF?

Back 108

Donnan effect
- negative charges on plasma proteins attract positively charged ions and repell negatively charged ones.

Front 109

treatment of SIADH?

Back 109

demeclocyclene, water restriction

Front 110

How are ECF, ICF, ECF osm, Hct, and [Na+] affected by:
hyperosmotic volume expansion?

Back 110

ECF increase
ICF no change
ECF osm increase
Hct decrease
[Na+] increase

Front 111

how does vasoconstriction of renal arterioles affect RBF? how is this achieved?

Back 111

decreases RBF
SNS

Front 112

What is the action of furosemide?

Back 112

Loop diuretics
- block Na+/K+/2Cl- cotransporter in the thick ascending limb of the Loop of Henle

Front 113

clearance
- definition (1)
- equation (2)

Back 113

1 = amount of plasma cleared of a substance per unit time
2 - C = UV/P

Front 114

What is the normal value for the filtration fraction?

Back 114

20% (that is, 20% of RPF is filtered)

Front 115

Mechanisms of aldolsterone causing K+ wasting (kaliuretic)

Back 115

- electrical coupling with Na+ influx
- insertion of additional Na+/K+ channels
- intracellular alkalosis

Front 116

What are some markers for plasma volume?

Back 116

Substances that distribute in plasma but not in interstitial fluid, because they are too large to cross capillary walls. These substances include radioactive albumin and Evans blue (dye that binds to albumin).

Front 117

What part of nephron is this?

- apical brush border microvilli
- basal infoldings with lots of mitochondria
- function: absorption of fluid

Back 117

proximal tubule

Front 118

renal blood flow is what % of CO?

Back 118

~25%

Front 119

How are ECF, ICF, ECF osm, Hct, and [Na+] affected by:
hyperosmotic volume contraction?

Back 119

ECF decrease
ICF decrease
ECF osm increase
Hct no change (brs pys p.155)
[Na+] increase

Front 120

how does AII affect renal arterioles

Back 120

preferentially constricts efferent arterioles unless it is a situation where there is a massive hemorrhage. then, so much AII is released that it constricts both efferent and afferent arterioles

Front 121

What stimulates Na+/K+/2Cl- cotransporter in the thick ascending limb of the Loop of Henle? what inhibits it?

Back 121

- ADH stimulates it
- Loop diuretics (furosemide) inhibits it

Front 122

renal blood flow (RBF)
- (1) % of CO
- proportional to pressure diff. between (2) and (3)
- inversely proportional to resistance of (4)

Back 122

1 = 25$
2 = renal artery and renal vein
4 = renal vasculature

Front 123

If the FF is increased, what effect does this have on reabsorption in the proximal tubule? What if it is decreased?

Back 123

Increases and decreases proximal tubule reabsorption, respectively

Front 124

Increase in UFR ___ (stimulates/inhibits) K+ secretion.

Back 124

stimulate
- increase flow rate -> decrease tubular [K+] -> favor secretion
- increase flow rate -> larger Na+ delivery to distal tubule -> increased Na+ absorption and K+ secretion by Na+/K+ transporters

Front 125

How do you calculate ICF volume? Interstitial fluid volume?

Back 125

Since there are no unique markers, ICF volume is calculated as the difference between total body water and ECF volume. Interstitial fluid volume is the difference between ECF volume and plasma volume.

Front 126

What part of nephron is this?

- simple squamous epithelium
- function: selective salt absorption

Back 126

thin part of Loop of Henle (diluting segement)

Front 127

at low [ang II], what effect on renal arterioles?

Back 127

preferential dilation of efferent arteriole--> protects GFR

Front 128

How are ECF, ICF, ECF osm, Hct, and [Na+] affected by:
hypoosmotic volume expansion?

Back 128

ECF increase
ICF increase
ECF osm decrease
Hct no change
[Na+] decrease

Front 129

how does ACE affect renal arterioles

Back 129

preferentially constricts efferent arterioles

Front 130

What is the action of thiazide?

Back 130

diuretics
- block Na+/Cl- cotransporter at the cortical diluting segment (early distal tubule)

Front 131

angiotensin II preferentially constricts (1) arteriole causing an (2) in GFR

Back 131

1 = efferent arteriole
2 = increaes

Front 132

What is the formula for GFR?

Back 132

GFR = Kf [(Pgc - Pbs) - (PIgc - PIbs)]
Note that PIbs is typically 0 because there should be no protein in Bowman's space

Front 133

What type of cell is most active during K+ depletion?

Back 133

type A intercalated cell
- active uptake of K+ by H+/K+ pump

Front 134

What is the ECF volume determined by?

Back 134

The volume of a body fluid compartment depends on the amount of solute it contains. Since the major cation of ECF is Na+ (with accompanying anions Cl- and HCO3-), ECF volume is determined by the amount of NaCl and NaHCO3 (sodium bicarbonate) it contains.

Front 135

What part of nephron is this?

- simple cuboidal epithelium
- basal infoldings with mitochondria
- function: selective salt absorption

Back 135

thick ascending limb of Loop of Henle (diluting segement)

Front 136

over what range of pressures does renal blood flow remain constant (autoregulation)

Back 136

80-200mmHg (thanks to myogenic mech and tubuloglomerular feedback)

Front 137

How are ECF, ICF, ECF osm, Hct, and [Na+] affected by:
hypoosmotic volume contraction?

Back 137

ECF decrease
ICF increase
ECF osm decrease
Hct increase (brs pys p155)
[Na+] decrease

Front 138

what effects does AII have on GFR?

Back 138

increases it

Front 139

What is the action of spironolactone and amiloride?

Back 139

K+ sparing diuretics
- inhibits Na+ transporter in the principle cells of the collecting duct
- inhibit K+ secretion in the principle cells of collecting duct

Front 140

vasodilation of renal arterioles causes an (1) in RBF and is caused by: (2), (3), (4) and (5)

Back 140

1 = increase
2 = PGE2, PGI2
3 = bradykinin
4 = NO
5 = dopamine

Front 141

How does the glomerular barrier contribute to Kf?

Back 141

Kf is the filtration coefficient, and it is maintained by the size barrier and the charge barrier (anionic glycoproteins inhibit the passage of negatively charged plasma proteins)

Front 142

What causes water diuresis?
What causes osmotic diuresis?

Back 142

- water diuresis: absence of ADH
- osmotic diuresis: increased excretion of a solute

Front 143

What is the normal value for osmolarity of the body fluids?

Back 143

290 mOsm/L (~300 mOsm/L for simplicity)

Front 144

What part of nephron is this?

- small apical brush border
- basal infoldings and mitochondria
- function: selective water/salt absorption

Back 144

distal tubule

Front 145

How measure renal plasma flow?

Back 145

use PAH, which is both filtered and secreted by renal tubules (so that~none in renal veins); this is the effective RPF

Front 146

The equation to calculate clearance is?

Back 146

The equation to calculate ______ is = UV/P.

Front 147

what effect do ACE-I have on GFR

Back 147

decreass it by dilating efferent arterioles

Front 148

What are some actions of aldolsterone on distal tubules and collecting duct?

Back 148

1) on principle cells:
- increases Na+ reabsorption
- increase K+ secretion
2) on intercalated cells
- increases H+ secretion

Front 149

autoregulation of RBF

Back 149

maintains a constant range of arterial pressure between 80 -200 mmHg

Front 150

What happens to Kf in glomerular disease?

Back 150

It decreases because the anionic charges on the barrier are lost, resulting in proteinuria

Front 151

Drugs that cause natriuresis.

Back 151

- acetazolamide (weak): inhibition of carbonic anhydrase
- loop diuretics
- thiazide
- K+ sparing diuretics

Front 152

What is the equation to estimate plasma osmolarity?

Back 152

Plasma Osmolarity (mOsm/L) =

2 x Plasma Na + Glucose/18 + BUN/2.8

Front 153

Type A or B intercalated cell of the collecting duct?

- acid secreting

Back 153

type A

Front 154

filtration fraction?

Back 154

GFR/RPF (normal~0.20)

Front 155

Renal blood flow is decreased by?

Back 155

___________ is decreased by sympathetic activation and angiotension II.

Front 156

what does afferent arteriole constriction do to RPF?

Back 156

decreases

Front 157

List some drugs that act directly on Na+ reabsorption.

Back 157

- loop diuretics: block Na+/K+/2Cl- on thick ascending loops of Henle
- thiazide diuretics: block Na+/Cl[ on early distal tubule
- K+ sparing diuretics: block Na+ absorption and K+ secretion on principle cells

Front 158

myogenic mechanism of autoregulation of RBF

Back 158

renal afferent arterioles contract in response to stretch

Front 159

What is the principal determinant of Pbs (hydrostatic pressure of Bowman's space)?

Back 159

Constriction of the ureters

Front 160

Why do loop diuretics cause stronger natriuresis than acetazolamide(carbonic anhydrase inhibitor)?

Back 160

- loop diuretics inhibit tubuloglomerular feedback
- loop diuretics disrupt the corticopapillary gradient

Front 161

Why is the Na+ concentration multiplied by 2 in the equation?

Back 161

Na+ must be balanced by an equal concentration of anions (Cl- and HCO3-).

Front 162

Type A or B intercalated cell of the collecting duct?

- HCO3- secreting

Back 162

type B

Front 163

where does acetozolamide work in kidney?

Back 163

(carbonic anhydrase inhibitor) works in PCT to inhibit resorption of HCO3- (w/o bicarb, don't have H+ needed for Na-H antiport) (N.B. can also tx acute mountain sickness)

Hint 163

None

Front 164

GFR is protected by low doses of?

Back 164

_________ is _______ by low doses of angiotension II (via selective efferent vasoconstriction).

Front 165

what does efferent artiorole constriction do to GFR?

Back 165

increases (by increasing Pgc)

Front 166

ECF volume contraction ___ (increase/decrease) reabsorption in proximal tubules.

Back 166

increase
- volume contraction -> increase peritubular capillary osmolarity and decrease Pcap -> reabsorption

Front 167

tubuloglomerular feedback

Back 167

increased renal arterial pressure leads to increased delivery of fluid to macula densa; macula densa causes constriction of nearby afferent arteriole

Front 168

What happens to the glomerular capillary oncotic pressure as we go along the length of the capillary?

Back 168

It increases because as water is filtered out, the protein concentration is increased

Front 169

How do loop diuretics, thiazide cause K+ wasting?

Back 169

natriuresis -> more Na+ delivered to distal tubule and collecting duct -> stimulation of Na+/K+ exchanger -> more K+ secreted -> hypokalemia

Front 170

What does volume contraction and volume expansion mean?

Back 170

Volume contraction means a DECREASE in ECF volume.

Volume expansion means an INCREASE in ECF volume.

Front 171

Name the two capillary bed in the kidney and what are the main function of each capillary bed?

Back 171

- glomerulus: filtration
- peritubular capillary: absorption

Front 172

middle/late PCT vs. early PCT?

Back 172

early PCT--Na resorb.coupled with glucose, aa, phosphate, etc.; mid/late PCT--Na resorb.w/ Cl-

Front 173

The kidney receives how much CO?

Back 173

25%

Front 174

what does increased plasma protein do to GFR?

Back 174

decreases it by increasing osmotic pressure in GC

Front 175

ECF volume expansion ___ (increase/decrease) reabsorption in proximal tubules.

Back 175

decrease
- volume expansion -> decrease peritubular capillary osmolarity and increase Pcap -> less reabsorption

Front 176

para-aminohippuric acid (PAH) is used to measure (1); PAH is both (2) and (3) by renal tubules

Back 176

1 = effective renal plasma flow
2 = filtered
3 = secreted

Front 177

What is the equation for filtered load?

Back 177

Filtered load = GFR x plasma conc

Front 178

What is a good drug of choice for treating life-threatening edema of the lung and brain?

Back 178

loop diuretics and thiazide
- high ceiling level

also good in treating congestive heart failure and hypertension

Front 179

What does a hyperosmotic disturbance mean?

Back 179

There has been an increase in ECF osmolarity.

Front 180

Equation for filtration pressure Pfil.

Back 180

Pfil = (P(cap) - P(bs)) - (O(cap) - O(bs))

because O(bs) = 0, so
Pfil = (P(cap) - P(bs)) - O(cap)

Front 181

where do K+sparing diuretics work?

Back 181

in CCD

Front 182

Renal arterioles are vasodilated by stimulation with?

Back 182

Renal arterioles are _______ by stimulation with PGE1, PGI2, bradykinin. nitric oxide, and dopamine.

Front 183

what does decreased plasma protein do to GFR?

Back 183

increases it by decreasing osmotic pressure in GC

Front 184

Cell types on late distal and collecting duct and their specialzed transporters.

Back 184

1) principle cells:
- Na+ reabsorption
- K+ secretion
- H2O reabsorption in the presence of ADH
2) Type A intercalated cells
- apical: H+ pump, K+ reabsorption during K+ depletion
- basalateral HCO3-/Cl- exchanger
3) Type B intercalated cells
- apical HCO3-/Cl- exchanger
- basalateral H+ pump

Front 185

Formula for RPF

Back 185

RPF = C pah = U(pah)V(pah) / Ppah

Front 186

What is the equation for excretion rate?

Back 186

Excretion rate = urine flow rate x urine conc

Front 187

What is the compatible blood pH range?

Back 187

7-7.8

Front 188

What does a hyposmotic disturbance mean?

Back 188

There has been a decrease in ECF osmolarity.

Front 189

Equation for GFR using Pfil.

Back 189

GFR = Kfil x Pfil
- Kfil = Lp x A
- Pfil = (P(cap) - P(bs)) - (O(cap)

Front 190

role of alpha intercalated cells?

Back 190

secrete H+ and resorb. K+ if hypokalemic (or acidic?)

Front 191

The myogenic mechanism for renal autoregulation is?

Back 191

changes in renal artery pressure as sensed as changes in stretch, and the afferent arteriole contracts to maintain RBF.

Front 192

what does increased plasma protein do to RBF?

Back 192

nothing

Front 193

What is this disease?

- impaired reabsorption of di-basic AA such as lysine, arginine, ornithine, cystein

Back 193

cysinuria (AR)
- see cystein stones (calculi)

Front 194

Formula for RBF

Back 194

RPF / (1 - Hct)

Front 195

What is the equation for reabsorption rate?

Back 195

Reabsorption rate = filtered load - excretion rate

Front 196

What is the most abundant acid in the body?

Back 196

CO2

Front 197

What are some examples of Isosmotic Volume Contraction?

Back 197

Diarrhea, burn.

Front 198

What are the two mechanism of autoregulation of GFR?

Back 198

1. myogenic: decreased systemic BP -> stretch reflex -> vasoconstriction -> maintain constant renal pressure. RBF remains constant over the range of arterial pressures from 80 to 200.
2. tubuloglomerular response: increased [Na+] sensed by macula densa -> constriction of afferent arteriole -> decrease GFR

Front 199

what cell is responsible for excreting K+ in hyperkalemia?

Back 199

principal cell (via Na-K ATPase and K channels)

Front 200

The tubuloglomerular feedback mechanism for renal autoregulation is?

Back 200

increased renal artery pressure increase fluid flow to macula densa, which signals afferent vasoconstriction to maintain RBF.

Front 201

what does decreased plasma protein [] do to RBF?

Back 201

nothing

Front 202

What is this disease?

- defective AA transport resulting in Tryptophan deficiency

Back 202

Hartnup's disease (AR)

Front 203

What substance can you use to measure GFR? Why?

Back 203

inulin
-bc it is filtered but it is NOT secreted or reabsorbed

Front 204

What is the equation for secretion rate?

Back 204

Secretion rate = excretion rate - filtered load

Front 205

What are the sources of each of the following acid?

- phosphoric acid
- sulfuric acid
- uric acid
- carboxylic acid

Back 205

- phosphoric acid: lipid, nucleic acid
- sulfuric acid: AA. low pKa, minimal excretion
- uric acid: purines. low pKa, minimal excretion
- carboxylic acid:ketoacidosis, lactic acidosis

Front 206

What are other consequences of diarrhea?

Back 206

Increased hematocrit and increased plasma protein concentration, which are explained by the loss of isosmotic fluid from the ECF compartment.

Front 207

Equation for excretion.

Back 207

excretion = filtration + secretion - absorption

Front 208

where is phosphate resorbed?

Back 208

only in PCT. ~15% of filtered phosphate excreted (imp for buffering later on)

Front 209

Renal plasma flow (RPF) is measured with?

Back 209

_______ is measured with para-aminohippuric acid (PAH).

Front 210

what does efferent arteriole constriction do to RBF?

Back 210

decreases it

Front 211

Describe K+ reabsorption/secretion along the nephron and the specific transporters.

Back 211

1) proximal tubule: 67% reabsorption
2) thick ascending limb of the loop of Henle: 20%
- Na+/K+/2Cl- cotransport
3) distal tubule and collecting duct
- reabsorption by type A intercalated cell:
- secretion by principle cells: determined by concentration gradient

Front 212

blood urea nitrogen and serum creatinine (1) when GFR (2)

Back 212

1 = increase
2 = decreases

Front 213

How can you tell if a substance is reabsorbed? Excreted?

Back 213

If it is reabsorbed, excretion rate is lower than filtered load. If it is secreted, excretion is higher than filtered load

Front 214

On normal western diet, how much fixed acids are excreted by the kidney?

Back 214

50-70 mmol

Front 215

What are some examples of Hyperosmotic Volume Contraction?

Back 215

Sweating, fever, diabetes insipidus.

Front 216

Equation for GFR using UFR.

Back 216

GFR = (U/P) x UFR

Front 217

effect of PTH on phosphate in kidney?

Back 217

PTH inhibits phosphate resorb. in PCt via inc'd AC-->cAMP. (get phosphaturia and inc'd urinary cAMP)

Front 218

Renal blood flow is calculated?

Back 218

____ = RPF/(1-Hct)

(1-Hct) is the fraction of blood volume occupied by plasma.

Front 219

what happens to the filtration fraction in afferent arteriole constriction?

Back 219

(GFR/RBF)
GFR decreases, RBF decreases
FF no change

Front 220

Factors that increase K+ secretion by the principal cells.

Back 220

- high K+ diet: high intracellular [K+] -> high driving force
- aldolsterone: stimulate Na+, K+ channels on principal cells
- alkalosis: too little H+ in blood -> H+ leaves the cells and K+ enters the cell from basalateral membrane -> increased driving force
- thiazide and loop diuretics: increase flow rate in distal tubule -> dilution of luminal [K+] -> increased driving force
- luminal anions: negativity of the lumen drives K+ out

Front 221

formula for filtration fraction

normal value for filtration fraction

Back 221

filtration fraction = GFR / RPF

normal = 0.20

Front 222

What is the conversion factor between ml and dl?

Back 222

100 ml = 1 dl

Front 223

Where are HCO3- absorption in the nephron?

Back 223

- 90% in proximal tubule: Na+/H+ exchanger, brushborder carbonic anhydrase. Luminal pH = 6.7
- rest is absorned in distal tubule and collecting duct (intercalated cells: absorption in typeA, secretion in typeB cells). Final pH 4.5

Front 224

What occurs during water deprivation?

Back 224

Hyperosmotic Volume Contraction:

Sweat is hyposmotic relative to ECF. Since a hyposmotic fluid is lost from ECF, ECF volume decreases and ECF osmolarity increases. The difference in osmolarity between ECF and ICF causes water to shift from ICF to ECF until the osmolarities are equal. In the new steady state, both ECF and ICF volumes will be decreased, and both osmolarities will be increased and equal to each other.

Front 225

What is the normal serum creatinine level? what about normal urine content?

Back 225

Ccr = 90 uM
urine content = U x UFR = 11 uM/min

Front 226

which diuretics can be used to treat hypercalcemia?

Back 226

loop diuretics

Front 227

In prerenal azotemia the change in the BUN:Cr is ___ because?

Back 227

The change in _______ is >20 because BUN increases more than Cr (as BUN is partially reabsorbed).

Front 228

what happens to FF in efferent arteriole constriction

Back 228

GFR/RBF
GFR increases, RBF decreases
FF increases

Front 229

Factors that decrease K+ secretion by the principal cells.

Back 229

- low K+ intake: low intracellular [K+] -> small driving force
- hypoaldolsterone: no stimulation of Na+, K+ channels on principal cells
- acidosis: excess H+ in blood -> H+ enters cell and K+ leaves through basalateral membrane -> low intracellular [K+] -> small driving force
- K+ sparing diuretics: decrease K+ secretion by blocking K+ channel on principal cells

Front 230

increase in filtration fraction produces an (1) in protein conc. of peritubular capillary blood, which causes (2)

Back 230

1 = increased
2 = increased reabsorption in proximal tubule

Front 231

How is glucose reabsorbed?

Back 231

Na-glucose cotransport in the proximal tubule reabsorbs Na and glucose from the lumen. Note that the number of these cotransporters is limited

Front 232

What is the max [HCO3-] before you see it in the urine?

Back 232

30mM

Front 233

What happens to the plasma protein concentration and hematocrit during hyperosmotic volume contraction? Why?

Back 233

Plasma protein concentration is increased, but the hematocrit is unchanged.

The hematocrit remains the same because even though ECF loses volume, the blood cells ALSO lose volume (ICF volume shift). The two effects offset each other.

Front 234

PAH clearance is close to what value?

Back 234

PAH is filtered and secreted
Clearance close to RPF

Front 235

which diuretics can be used to treat hypercalciURIA

Back 235

thiazides (increase Ca resorb.)

Front 236

Filtration fraction is calculated as ________ and is normally?

Back 236

___ = GFR/RPF

Normally is 0.20

Front 237

what happens to FF in increased plasma protein concentraton

Back 237

GFR/RBF
GFR decreases, RBF no change
FF decreases

Front 238

Specialized transporters on type B intercalated cells in the late distal tubule and collecting duct.

Back 238

- apical: Cl-/HCO3- exchanger
- basalateral: H+(out) and Cl(out) transporter.

Front 239

glomerular barrier
- components (1)
- lined with? (2)

Back 239

1 = capillary endothelium
basement membrane
filtration slits of podocytes

2 = anionic glycoproteins (prevent proteins from passing through)

Front 240

What is the transport maximum?

Back 240

The reabsorptive rate at which all available transporters are saturated and no further reabsorption can occur, so excess solute will be excreted in the urine

Front 241

What can cause a left shift of HCO3- curve?

Back 241

- alkalosis
- volume expansion

Front 242

What are some examples of Hyposmotic Volume Contraction?

Back 242

Adrenal insufficiency

Front 243

Glucose clearance is close to what value?

Back 243

zero
- glucose is filtered and absorbed

Front 244

Rank the following in decreasing clearance.

- PAH
- inulin
- Na+
- K+
- glucose/AA/HCO3-
- urea

Back 244

PAH
K+
inulin
urea
Na+
glucose/AA/HCO3-

Front 245

relationship of K+ and NH3?

Back 245

hyperkalemia inhibits NH3 synthesis (RTA type 4), dec'd H+ excretion; hyPOkalemia--stim NH3 synthesis

Front 246

If the filtration fraction increases, you will see what in the peritubular capillary network?

Back 246

The protein concentration will increase in the peritubular capillaries and there will be increased PT reabsoption.

Front 247

what happens to FF in decreased plasma protein []

Back 247

GFR/RBF
GFR increases, RBF no change
FF increases

Front 248

T/F: There is no active transport in thin loop of Loops of Henle.

Back 248

T.

Front 249

glomerular capillary hydrostatic pressure
- increased by dilation of (1) and constriction of (2)

Back 249

1 = afferent arteriole
2 = efferent arteriole

Front 250

What is the Tm for glucose?

Back 250

Under 250 mg/dl, all filtered glucose is reabsorbed because there are plenty of carriers. Over 350 mg/dl, the carriers are entirely saturated, so increased plasma concentration doesn't result in increased reabsorption. The threshold (where glucose first begins to appear in the urine) is about 250 mg/dl

Front 251

What can cause a right shift of HCO3- curve?

Back 251

- acidosis
- volume depletion

Front 252

What occurs during adrenal insufficiency?

Back 252

Hyposmotic Volume Contraction:

Adrenal insufficiency results in aldosterone deficiency, which leads to excess NaCl excretion in the urine. NaCl is an ECF solute, so ECF osmolarity decreases. This causes water to shift from ECF to ICF until both osmolarities are decreased and equal. In the new steady state, both ECF and ICF osmolarities will be lower than normal and equal to each other. ECF volume will be decreased and ICF volume will be increased.

Front 253

How does aging affect the following?

- GFR

Back 253

decreases

Front 254

ECF volume contraction and acid/base balance?

Back 254

ECF volume contraction-->HCO3- resorb. , contraction alkalosis (N.B. in vomiting, met alk made worse if ECF vol contracts!)

Hint 254

None

Front 255

Decreases in the filtration fraction result in?

Back 255

decreases in protein concentration (ie oncotic pressure) or peritubular capillarys, and less PT reabsorption.

Front 256

what happens to FF when ureter is constricted?

Back 256

GFR/RBF
GFR decreases, RBF no change
FF decreases

Front 257

How does PTH affect phosphate transport in proximal tubule?

Back 257

PTH lowers Tmax for phosphate thus increases excretion and leads to low level of phosphate in the body.

Front 258

bowman's space hydrostatic pressure
- increased by constriction of (1)

Back 258

1 = ureters

Front 259

What is "splay?"

Back 259

The region of the solute titration curve (Tm curve) between threshold and Tm. It represents the excretion of solute in the urine before saturation of reabsorption occurs

Front 260

What can cause volume depletion alkalosis? Is it easy to correct?

Back 260

volume depletion alkalosis
- constant vomit: loss of acid and volume at the same time
- alkalosis hard to correct because volume depletion shifts HCO3- excetion to the right.

Front 261

What happens to the plasma protein concentration and hematocrit during hyposmotic volume contraction? Why?

Back 261

Both plasma protein concentration and hematocrit will be increased because of the decrease in ECF volume. Hematocrit increases also because of the shift of water into red blood cells, increasing cell volume.

Front 262

How does aging affect the following?

- plasma [creatinine]

Back 262

no change
- decreased GFR -> increased [creatinine]
- decreased muscle mass -> decreased [creatinine]
- so overall no change in [creatinine]

Front 263

why might you get tingling, numbness, muscle spasms in respiratory alkalosis?

Back 263

signs/symptoms of hypocalcemia, b/c H+ and Ca2+ compete for protein binding sites and dec'd H+ means more bound Ca and less free Ca (~hypocalc.)

Front 264

The GFR formula?

Back 264

____ = Kf [(Pgc - Pbs) - (ONCgc-ONCbs)]

K x (hydrostatic p - oncotic p)

Front 265

what things are reabsorbed in the PCT?

Back 265

glucose
AA's
most of the HCO3

Front 266

What can you do to treat barbituates poisoning?

Back 266

HCO3- infusion to make the tubular fluid more alkaine
- barbituric acid in charged form -> absorption of barbituric acid blocked

Front 267

glomerular capillary oncotic pressure
- increases along (1) due to increased (2)

Back 267

1 = length of glomerular capillary bed
2 = increased protein conc.

Front 268

How can you promote excretion of weak acids?

Back 268

Alkalinization of the urine will deprotonate the acid (that is, you'll have the A- form instead of the HA form), which is less able to diffuse from the urine to the blood

Front 269

Name the two mechanisms that fixed acids are excreted.

Back 269

- titratable acid: di-basic phosphate
- ammonium: glutamine -> NH3 -> NH4+ -> Na+/NH4+ exchanger

Front 270

What are some examples of Isosmotic Volume Expansion?

Back 270

Infusion of isotonic NaCl.

Front 271

Equation for filtration fraction FF.

Back 271

FF = GFR/RPF

Front 272

effect of insulin on K+?

Back 272

insulin deficiency--> shift of K+ out of cells, hyperkalemia; insulin-->shift of K+ into cells, hypokalemia

Front 273

What are the breakdowns of RPF, GFR, and RBF?

Back 273

RPF is about 600 mL entering afferent aa. GFR is about 20% of that, or 125 mL filtered across glomeruli. RBF is the remainder that perfusses the kidney, about 475 mL.

Front 274

describe how HCO3 is handled in PCT

Back 274

HCO3 is in the lumen and combines with H that is secreted into the lumen --> H2CO3
Carbonic anhydrase --> H20 + CO2
which re-enters the tubule and reforms as H2CO3 with CA
the H is then secreted into the lumen and the HCO3 is reabsorbed

Front 275

How are weak organic acids secreted in the late proximal tubules?

Back 275

- basalateral side: transporter takes up the acid
- apical: anion transporter to secrete the acid (site where different drug may compete)

Front 276

constriction of afferent arteriole:
- (1) GFR
- (2) RPF
- (3) filtration fraction

Back 276

1 = decreases
2 = decreases
3 = no change

Front 277

What does it mean if TF/P > 1?

Back 277

There has been secretion, so the concentration in the tubular fluid is higher than that in the plasma

Front 278

pKa of phosphate and NH4+.

Back 278

- pKa (phosphate) = 6.8
- pKa (NH4+) = 9.3

Front 279

What occurs during an infusion of isotonic NaCl?

Back 279

Isosmotic Volume Expansion:

Since NaCl is an extracellular solute, all of the isotonic NaCl solution is added to the ECF, causing an increase in ECF volume, but no change in ECF osmolarity. There will be no shift of water between ICF and ECF.

Front 280

What is the FF under normal condition?

Back 280

20%
- 20% of RPF is filtered

Front 281

What are the effects on GFR, RPF, and FF when changing Starling Forces by: afferent constriction (ie sympathetics)?

Back 281

GFR decrease
RPF decrease
FF no change

Front 282

what happens in the TAL?

Back 282

NKCC pump (blocked by furosemide): aids in reabsorbing Na, Cl, K
K flows back out into lumen and the gradient drives the absorption of Mg and Ca
also aids in the running of the NKCC pump

Front 283

How are weak organic bases secreted in the late proximal tubule?

Back 283

- basalateral: transporter taken up the base
- apical: organic cation/H+ exchanger

ex. creatinine, EPI, NE, atropine, amiloride

Front 284

constriction of efferent arteriole:
- (1) GFR
- (2) RPF
- (3) filtration fraction

Back 284

1 = increases
2 = decreases RPF
3 = increases

Front 285

What is the significance of TF/Pinulin, and what is the equation?

Back 285

Marker for water absorption
% of filtered water that is reabsorbed = 1 - [1 / (TF/Pinulin)]

Front 286

Where is ammonium reabsorbed?

Back 286

- thick ascending limb
- medullary collecting duct

Front 287

What happens to the plasma protein concentration and hematocrit during isosmotic volume expansion? Why?

Back 287

Both plasma protein concentration and hematocrit will decrease (i.e., be diluted) because of the increase in ECF volume.

Front 288

Effect of decreased GFR on the following.

- Pgc
- O(gc)

Back 288

higher Pgc
lower Ogc

Front 289

What are the effects on GFR, RPF, and FF when changing Starling Forces by: efferent constriction (angiotension II)?

Back 289

GFR increase
RPF decrease
FF increase

Front 290

is the TAL permeable to water

Back 290

no

Front 291

Where is urea reabsorbed?

Back 291

- proximal tubule: passively
- inner medullary collecting duct: in the presence of ADH, contributes to corticopapillary osmotic gradient.

Front 292

increased plasma protein causes:
- (1) GFR
- (2) RPF
- (3) filtration fraction

Back 292

1 = decreased
2 = no change on RPF
3 = decreased FF

Front 293

How much filtered Na is reabsorbed?

Back 293

Over 99% (less than 1% of filtered load is in the urine)

Front 294

What happens to acid excretion during acidosis?

Back 294

- stimulate enzyme in deamination of glutamine
- increase amount of titratable acid

Front 295

What are some examples of Hyperosmotic Volume Expansion?

Back 295

High NaCl intake.

Front 296

Kfil is ____ (increased/decreased) in glomerulonephritis, diabetic nephropathy, and glomerulosclerosis.

Back 296

decreased

Front 297

What are the effects on GFR, RPF, and FF when changing Starling Forces by: increased plasma protein?

Back 297

GFR decrease
RPF no change
FF decrease

Front 298

what is the thin descending loop permeable to?

Back 298

water, but not Na

Front 299

Where is phosphate reabsorbed?

Back 299

- 85% in proximal tubule by Na+/PO4- cotransporter
- 15% excreted

* PTH decreases Tmax thus decreases reabsorption and increase excretion (phosphaturia and urinary cAMP)

Front 300

ureteral stone causes:
- (1) GFR
- (2) RPF
- (3) filtration fraction

Back 300

1 = decreased GFR
2 = no change RPF
3 = decreased FF

Front 301

How much Na is reabsorbed in the proximal convoluted tubule?

Back 301

67%

Front 302

What happens to acid excretion during diabetic ketoacidosis?

Back 302

- stimulate enzyme in deamination of glutamine
- increase amount of titratable acid
- additional proton acceptor in the urine (beta-hydroxybutyrate, acetoacetate)

Front 303

What occurs during high NaCl intake?

Back 303

Hyperosmotic Volume Expansion:

After ingesting a lot of NaCl (i.e., eating a bag of potato chips), there will be an increase in the amount of solute in the ECF, which increases the ECF osmolarity. ECF osmolarity is higher than ICF osmolarity, which causes water to shift from ICF to ECF, decreasing ICF volume. Both ECF and ICF osmolarities are higher than normal and equal.

Front 304

How does ADH affect Kfil?

Back 304

ADH -> mesangial cell contract -> decreases A(surface area) -> lower Kfil -> lower GFR

Front 305

What are the effects on GFR, RPF, and FF when changing Starling Forces by: a ureteral stone?

Back 305

GFR decrease
RPF no change
FF decrease

Front 306

what is happens in the early distal convaluted tubule

Back 306

actively reabsorbs Na, Cl
Ca absorption is controlled by PTH receptors found here

Front 307

Mechanism of action of PTH on phosphate reabsorption.

Back 307

PTH decreases Tmax thus decreases reabsorption and increase excretion (phosphaturia and urinary cAMP)
- activate adenylate cyclase -> increase cAMP -> inhibit Na+/PO4- cotransport.

Front 308

formula for filtered load

Back 308

filtered load = GFR x plasma conc.

Front 309

How much Na is reabsorbed in the thick ascending limb of the loop of Henle?

Back 309

25%

Front 310

Henderson-Hasselbach equation for calculating pH in bicarbonate buffer system.

Back 310

pH = 6.1 + log ([HCO3]/(0.3xPCO2))

Front 311

What happens to the plasma protein concentration and hematocrit during hyperosmotic volume expansion? Why?

Back 311

Both plasma protein concentration and hematocrit will be decreased due to the increase in ECF volume. Also, hematocrit will decrease because of the water shift out of the red blood cells into plasma.

Front 312

What is the change in the following with constriction of afferent arteriole?

- GFR
- RPF
- FF

Back 312

- GFR: down
- RPF: down
- FF: no change

Caused by decreased Pgc

Front 313

what happens in the collecting tubules

Back 313

Na is reabsorbed in exchange for K/H (regulated by ALDOSTERONE!!!)
reabsorption of water regulated by ADH (aquaporins)

Front 314

Mechanism that contributes to corticopapillary osmotic gradient.

Back 314

- countercurrent multiplication in loops of Henle: Na+/K+/2Cl- cotransport(augmented by ADH) in thick ascending loop with no H2O permeability.
- increased urea concentration in inner medulla: ADH increase urea absorption in inner medullary collecting duct
- countercurrent system of vasa recta in medulla: minimize washout of osmolytes from medullary interstitium

Front 315

excretion rate

Back 315

excretion rate = V x urine conc.

Front 316

How much Na is reabsorbed in the distal convoluted tubule?

Back 316

5%

Front 317

Equation for anion gap calculation.

Back 317

anion gap = [Na+] - [Cl-] - [HCO3] = 12mM (8-16mM)

Front 318

What are some examples of Hyposmotic Volume Expansion?

Back 318

Syndrome of inappropriate antidiuretic hormone (SIADH)

Front 319

What is the change in the following with constriction of efferent arteriole?

- GFR
- RPF
- FF

Back 319

- GFR: increase then decrease (due to tubuloglomerular regulation)
- RPF: decrease
- FF: increase

Caused by increased Pgc

Front 320

which part of the nephron is impermeable to water?

Back 320

TAL (and collecting tubule if there is no ADH)

Front 321

Where does ADH act on the nephron?

Back 321

- thick ascending limb: stimulate Na+/K+/2Cl- cotranport
- distal tubule and collecting duct: stimulate V2 receptor on basalateral membrane -> adenylate cyclase -> increase cAMP -> PKA -> insertion of aquaporins
- inner medullary collecting duct: increase urea absorption thus aid in corticopapillary osmotic gradient

* also stimulate V1 receptor in vasculature: vasoconstriction

Front 322

reabsorption rate

Back 322

reabsorption rate = filtered load - excretion rate

Front 323

How much Na is reabsorbed in the collecting duct?

Back 323

3%

Front 324

What can cause this?

- increased anion gap

Back 324

diabetic acidosis
- anion gap = [Na+] - [Cl-] - [HCO3]

Front 325

What occurs during syndrome of inappropriate antidiuretic hormone (SIADH)?

Back 325

Hyposmotic Volume Expansion:

Too much ADH leads to too much water reabsorption, and the excess water is retained and distributed throughout the total body water. The volume of water that is added to the ECF and ICF is in direct proportion to their original volumes. ECF and ICF volumes will be increased, and ECF and ICF osmolarities will be decreased.

Front 326

What is the change in the following with increased plasma protein?

- GFR
- RPF
- FF

Back 326

- GFR: decrease
- RPF: no change
- FF: decrease

Caused by increased Ogc

Front 327

where in kidney is EPO released from

Back 327

endo cells of peritubular capillaries

Front 328

What stimulate ADH release from posterior pituitary gland? what inhibits it?

Back 328

Stimulate ADH:
- stimulation of osmoreceptors in the wall of 3rd ventricle

Inhibition of ADH:
- stimulation of volume receptors in atria
- caffeine
- alcohol

Front 329

secretion rate

Back 329

secretion rate = excretion rate - filtered load

Front 330

How much filtered water is reabsorbed in the proximal tubule?

Back 330

67%

Front 331

What can cause this?

- normal anion gap

Back 331

HCL ingestion
- anion gap = [Na+] - [Cl-] - [HCO3]

Front 332

What happens to the plasma protein concentration and hematocrit during hyposmotic volume expansion? Why?

Back 332

Plasma protein concentration is decreased by dilution. However, the hematocrit is unchanged as a result of two offsetting effects: the concentration of RBCs decreases due to dilation, but RBC volume increases because water shifts into the cells.

Front 333

What is the change in the following with uretral stone?

- GFR
- RPF
- FF

Back 333

- GFR: decrease
- RPF: no change
- FF: decrease

Caused by increased Pps

Front 334

what enzyme converts 25-OH vitamin D to its active form?

Back 334

1-alpha hydroxylase

Front 335

Where is ADH released?

Back 335

posterior pituitary gland
- neucleus supraopticus
- nucleus paraventricularis

Front 336

where is glucose reabsorbed in nephron? what kind of transporter?

Back 336

proximal tubula

Na+ glucose cotransport

Front 337

What is glomerulotubular balance?

Back 337

The same FRACTION of solute is reabsorbed at all times, for all concentrations (that is, for any concentration, X% is always reabsorbed)

Front 338

How does kidney compensate for respiratory acidosis?

Back 338

- increase in HCO3 absorption: type A intercalated cell
- increase in H+ excretion: titratable acid, ammonium

Front 339

What is the definition of renal clearance?

Back 339

Renal clearance is the volume of plasma completely cleared of a substance by the kidneys per unit time.

Front 340

What is the change in the following with ACE inhibitors?

- GFR
- RPF
- FF

Back 340

ACE inhibitors dilate efferent arteriole
- GFR: increase then decrease
- RPF: no change
- FF: increase

Front 341

what do JG cells do?

Back 341

secrete renin in response to low renal blood pressure

Front 342

What happens when there is 1% reduction in plasma osmolarity?

Back 342

complete ADH block

Front 343

Tm for a carrier (1)

Tm of glucose = (2)

Back 343

1 =reabsorptive rate at which carriers are saturated
2 = 350 mg/dL

Front 344

What part of the nephron is the site of glomerulotubular balance?

Back 344

The proximal tubule

Front 345

How does kidney compensate for respiratory alkalosis?

Back 345

- spill over HCO3-: type B intercalated cell

Front 346

What is the equation for renal clearance?

Back 346

Cx = [U]xV/Px

Cx = clearance of X. Units are mL/min
[U]x = urine concentration of X
Px = plasma concentration of X

Front 347

what does the macula densa do?

Back 347

senses the amt of Na

Front 348

What happens when there is 1-2% increase in plasma osmolarity?

Back 348

maximum antidiuresis

Front 349

threshold (1)

threshold of glucose (2)

Back 349

1 = plasma conc. at which substance first appears in urine
2 = 250 mg/dL

Front 350

What does it mean for proximal tubule Na and water reabsorption to be isosmotic?

Back 350

The reabsorption of both Na and water in this region are exactly proportional, so osmolarity is maintained (both Na and water have TF/P ratios of 1.0 here)

Front 351

Name some etiology of metabolic acidosis.

Back 351

- diabetic ketoacidosis: increased production of acids
- aspirin overdose: ingestion of acids
- secretory diarrhea: loss of alkaline fluid
- renal failure: inability to excrete fixed acids

Front 352

Renal clearance is the ratio of ___________ to ____________.

Back 352

Renal clearance is the ratio of urinary excretion ([U]x*V) to plasma concentration.

Front 353

where is the macula densa

Back 353

part of the DCT

Front 354

What happens when plasma osmolarity is > 294 mOsM?

Back 354

exceeded thirst threshold, drink water

Front 355

splay

Back 355

region between threshold and Tm
--> represents excretion of glucose in urine before saturation of reabsorption (Tm) is full achieved

for glucose = between 250 and 350

Front 356

How is Na reabsorbed in the early proximal tubule?

Back 356

Na-Glucose cotransporter
Na-solute cotransport with various solutes
Na-H symporter

Front 357

Name some etiology of metabolic alkalosis.

Back 357

- lye poisoning: ingestion of alkali
- vomiting: loss of gastric juice
- volume depletion: retention of HCO3-.

Front 358

Which substance is freely filtered across the glomerular capillaries, but not reabsorbed or secreted?

Back 358

Inulin, which is used to determine the glomerular filtration rate (GFR).

Front 359

what do PGs do to the kidney

Back 359

vasodilate the afferent arterioles (that's why NSAIDS can --> ARF by inhibiting PG)

Front 360

Equation for osmotic clearance.

Back 360

Cosm = UFR x (U/P)osm

Front 361

where does secretion of PAH occur?

Back 361

proximal tubule

Front 362

How and where do carbonic anhydrase inhibitors work?

Back 362

By inhibiting CA, the reabsorption of HCO3 is decreased. These inhibitors (like acetazolamide) act in the proximal tubule, where H is secreted via Na-H antiport

Front 363

What can cause this?

- respiratory acidosis
- lactic acidosis

Back 363

severe asthma

- respiratory acidosis: insufficient expiration of CO2
- lactic acidosis: hypoxia

Front 364

What is the formula for Clearance Ratio?

Back 364

Clearance ratio = Cx/Cinulin

Front 365

what effect does aldosterone have on H

Back 365

more H is secreted

Front 366

Equation for free H2O clearance.

Back 366

C(H2O) = UFR - Cosm = UFR x (1 - (U/P)osm)

Front 367

which form of weak acid can back diffuse from urine to blood?

Back 367

HA - lipid soluble, uncharged

Front 368

How is Na reabsorbed in the late proximal tubule?

Back 368

Na-Cl symport

Front 369

What happens in acid/base balance when in altitude region?

Back 369

lack of O2 -> hyperventilate -> hypocapnea -> respiratory alkalosis -> decrease HCO3 absorption (kidney response) -> metabolic acidosis

Front 370

What does Cx/Cinulin = 1.0 mean?

Back 370

The clearance of substance x equals the clearance of inulin, and is neither reabsorbed or secreted.

Front 371

where does aldosterone work in kidney?

Back 371

DCT

Front 372

Compare H2O clearance during diuresis and antidiuresis.

- % reabsorption
- urine osmolarity
- UFR
- Cosm
- C(H2O))

Back 372

Diuresis (absence of ADH)
- 1% reabsorption in distal tubule
- 4% reabsorption in collecting duct
- urine osmolarity: 50-60 mOsM
- UFR: 12mL/min
- Cosm: 2.4 mL/min
- C(H2O)): 9.6 mL/min

Antidiuresis (presence of ADH)
- 10% reabsorption in distal tubule
- 4.6% reabsorption in collecting duct
- urine osmolarity: 1200 mOsM
- UFR: 0.5mL/min
- Cosm: 12 mL/min
- C(H2O)): -1.5 mL/min

Front 373

which form of weak base can back-diffuse from urine to blood?

Back 373

B form - uncharged, lipid soluble

Front 374

How does extracellular fluid volume influence Na reabsorption?

Back 374

If ECFV decreases, reabsorption is increased
If ECFV increases, reabsorption is decreased

Front 375

T/F: Metabolic acidosis may persist 1-2 days after descending from a high altitude region.

Back 375

T.

Front 376

What does Cx/Cinulin < 1.0 mean?

What substances show this property?

Back 376

The clearance of x is lower than inulin. It is either not filtered, or it is reabsorbed.

Albumin, Na+, Cl-, HCO3-, phosphate, urea, glucose, and amino acids.

Front 377

where does PTH work?

Back 377

PCT to decrease PO4 reabsorption
DCT to increase Ca reabsorption
stimulates 1-alpha hydroxylase in PCT

Front 378

When is C(H2O) zero?

Back 378

under treatment with loop diuretics
- no diluting effect
- no role in setting up corticopapillary gradient.

Front 379

TF/ P ratio = 1.0

Back 379

no reabsorption of substance (or reabsorption exactly proportional to water)

Front 380

How is Na reabsorbed in the thick ascending limb of the loop of Henle?

Back 380

Na-K-2Cl cotransporter

Front 381

What does Cx/Cinulin > 1.0 mean?

What substances show this property?

Back 381

The clearance of x is higher than inulin. It must be secreted.

Organic acids and bases, and sometimes K+.

Front 382

where is ACE released from?

Back 382

lung

Front 383

where does TF/P = 1,0?

Back 383

Bowman's space

Front 384

What inhibits the Na-K-2Cl cotransporter?

Back 384

Loop diuretics such as furosemide, ethacrynic acid, and bumetanide

Front 385

What percentage of cardiac output do the kidneys receive?

Back 385

25% of cardiac output.

Front 386

if TF/ P is less than 1.0

Back 386

reabsorption of substance has been greater than reabsorption of water

--> conc. in tubular fluid is less than plasma

Front 387

Is the thick ascending limb of the loop of Henle permeable or impermeable to water?

Back 387

Impermeable, so in this region, NaCl is reabsorbed without water. Therefore, this segment is known as the diluting segment.

Front 388

What effect do the sympathetic nervous system and circulating catecholamines have on RBF and GFR? Why?

Back 388

There is a decrease in both RBF and GFR.
Sympathetic nervous system produces vasoconstriction by activation of α1 receptors. α1 receptors are found on both afferent and efferent arterioles, but are much more prevalent on afferent arterioles.

Front 389

if TF/P is greater than 1.0

Back 389

either reabsorption has been less than water OR there has been secretion of substance

Front 390

What sort of potential difference is observed in the thick ascending limb of the loop of Henle?

Back 390

Lumen-positive

Front 391

What effect does Angiotensin II have on RBF and GFR?

Back 391

Angiotensin II vasoconstricts both arterioles. This causes a decrease in RBF.
However, efferent arterioles are more sensitive to angiotensin II. Thus, at low levels of angiotensin II, there is an increase in GFR. A high level of angiotensin II produces a decrease in GFR.

Front 392

Na+ reabsorption in PCT
- percent?
- along with?

Back 392

1 = 67%
2 = H20 - isosmotic

Front 393

How is Na reabsorbed in the early distal tubule?

Back 393

Na-Cl cotransporter

Front 394

What effect do prostaglandins have?

Back 394

Prostaglandins, produced locally in the kidneys, cause vasodilation of both afferent and efferent arterioles. This increases RBF, and opposes the effects of the sympathetic NS and angiotensin II.

Front 395

Na+ reabsorption in early PCT
- transporters? (2)

Back 395

1 = Na+ cotransport with glucose, amino acids, phosphate and lactate
2 = Na+ and H+ exchanger

Front 396

What inhibits the Na-Cl cotransporter of the early distal tubule?

Back 396

Thiazide diuretics

Front 397

What effect does dopamine have on renal arterioles?

Back 397

At low levels, Dopamine dilates renal arterioles, and has a protective (vasodilatory) effect on blood flow.

Front 398

Na+ reabsorption in late PCT

Back 398

Na+ reabsorbed with Cl-

Front 399

Is the early distal tubule permeable or impermeable to water?

Back 399

Impermeable

Front 400

How can renal plasma flow (RPF) be estimated?

Back 400

RPF can be estimated from the clearance of an organic acid para-aminohippuric acid (PAH).

Front 401

carbonic anhydrase inhibitors

Back 401

ex. acetazolaminde
- diuretics
- act on early PT
- inhibit reabsorption of filtered HCO3-

Front 402

What do the principal cells of the late distal tubule and collecting duct do?

Back 402

Reabsorb Na and water
Secrete K

Front 403

What is the formula for Effective RPF?

Back 403

Effective RPF = [U]PAH x V/[P]PAH = Clearance of PAH

Effective RPF is in ml/min

Front 404

ECF volume contraction (1) reabsorption; ECF volume expansion (2) proximal tubular reabsorption

Back 404

1 = increases reabsorption
2 = decreases reabsorption

Front 405

What effect does aldosterone have upon Na and K transport?

Back 405

Increases Na reabsorption and K secretion in the late distal tubule and collecting duct

Front 406

What is the difference between effective RPF and true RPF?

Back 406

Effective RPF underestimates true RPF by ~10%. This is because we assume the concentration of PAH in the renal vein is zero, when in reality it is nearly zero.

Front 407

Na+ reabsorption in Thick Ascending Loop of Henle
- percent? (1)
- transporter? (2)

Back 407

1 = 25%
2 = Na+ K+ 2Cl- transporter

Front 408

What effect does ADH have upon water permeability?

Back 408

It increases water permeability in the collecting duct by inducing the insertion of aquaporin 2 into the apical membrane. In the absence of ADH, the principal cells of the collecting duct are virtually impermeable to water.

Front 409

What is the formula for RBF?

Back 409

RBF = RPF/(1-Hematocrit)

Front 410

loop diuretics inhibit?

Back 410

Na+/K+/2Cl- cotransporter in TAL

ex. furosemide
ethacrynic acid
bumetanide

Front 411

What are K-sparing diuretics?

Back 411

Spironolactone, tiramterene, amiloride -- these decrease K secretion

Front 412

What constitutes the most significant barrier of the glomerular capillary?

Back 412

The basement membrane and its three layers: lamina rara interna, lamina densa, and lamina rara externa. The basement membrane does not permit filtration of plasma proteins, unlike the endothelial cell layer.

Front 413

What part of nephron is impermeable to water?

Back 413

thick ascending limb of loop of henle

Front 414

How is Na reabsorbed in the late distal tubule and collecting duct?

Back 414

Amiloride-sensitive Na channels

Front 415

What is the Starling Equation?

Back 415

GFR = Kf [(Pgc - Pbs) - πgc]

Kf = Hydraulic conductance or filtration coefficient

Pgc = Hydrostatic pressure in glomerular capillary

Pbs = Hydrostatic pressure in Bowman's space

πgc = Oncotic pressure in glomerular capillary

Front 416

What is Kf (filtration coefficient)? What are the two factors that contribute to Kf?

Back 416

The filtration coefficient is the water permeability or hydraulic conductance of the glomerular capillary wall.

The two factors that contribute to Kf are the water permeability per unit of surface area and the total surface area.

Front 417

Na+ reabsorption in distal tubule and collecting duct
- percent? (1)
- transporters? (2)

Back 417

1 = 8%
2 - Na+ Cl- co transport

Front 418

What do the intercalated cells of the late distal tubule and collecting duct do?

Back 418

Secrete H via an H-ATPase that is induced by aldosterone
Reabsorb K via an H-K-ATPase

Front 419

What other substances, besides inulin, can estimate GFR?

Back 419

Creatinine is the closest substance. It is freely filtered, but is also secreted to a small extent. The clearance of creatinine slightly overestimates the GFR.

Blood urea nitrogen (BUN) and serum creatinine concentration are also used to estimate GFR.

Front 420

thiazide diuretics inhibit?

Back 420

Na+ Cl- cotransporter in distal tubule/collecting duct

Front 421

What body compartment is the majority of K found in?

Back 421

The intracellular fluid

Front 422

What is the filtration fraction? What is the normal value?

Back 422

Filtration fraction = GFR/RPF

The normal value is about 0.20 or 20%.

Front 423

principal cells of late distal tubule/CD
- reabsorb? (1)
- secrete? (2)
- function increased by what hormone? (3)

Back 423

1 = Na+ and H20
2 = secrete K+
3 = aldosterone

Front 424

How do K shifts contribute to hypo/hyperkalemia?

Back 424

A shift of K OUT of the cells causes hyperkalemia
A shift of K INTO the cells causes hypokalemia

Front 425

What is the formula for filtered load?

Back 425

Filtered Load = GFR* [P]x

Front 426

ADH acts on (1) cells in (2) nephron segment to increase (3)

Back 426

1 = principal cells
2 = late DT and CD
3 = water permeability

Front 427

Is K filtered by the nephron? Secreted? Reabsorbed?

Back 427

Yes to all three

Front 428

What is the formula for excretion rate?

Back 428

Excretion rate = V x [U]x

Front 429

K+ sparing diuretics
ex. (1)
- function? (2)

Back 429

1 = spironolactone, triamterene, amiloride
2 = decrease K+ secretion in principal cells of late DT and CD

Front 430

How do we achieve K balance?

Back 430

When urinary excretion is exactly equal to dietary intake

Front 431

What is the formula for Reabsorption of Secretion rate?

Back 431

Reabsorption or Secretion Rate = Filtered load - Excretion Rate

Front 432

alpha-intercalated cells
- location? (1)
- function? (2)

Back 432

1 = late DT and CD
2 = secreted H+ and reabsorb K+ by an H+/K+ ATPase

Front 433

What are some causes of hyperkalemia (K shift out of cells)?

Back 433

Insulin deficiency
B-adrenergic antagonists
Acidosis
Hyperosmolarity
Na-K ATPase inhibitors
Exercise
Cell lysis

Front 434

At what plasma glucose concentrations does glucose start to be excreted in the urine?
What is this point called?

Back 434

At plasma glucose concentrations above 200 mg/dL.

This is called threshold.

Front 435

Causes of Hyperkalemia?

Back 435

insulin deficiency
B-adrenergic antagonists
acidosis
hyperosmolarity
inhibitors of Na+/K+ pump
exercise
cell lysis

Front 436

What are some causes of hypokalemia (K shift into cells)?

Back 436

Insulin
B-adrenergic agonists
Alkalosis
Hyposmolarity

Front 437

What is Tm?

Back 437

Tm (transport maximum) is the plasma glucose concentration when all glucose carriers are saturated and cannot reabsorb any more. This occurs at plasma concentrations above 350 mg/dL.

Front 438

Causes of Hypokalemia?

Back 438

insulin
B-adrenergic agonists
alkalosis
hypoosmolarity

Front 439

How much can K excretion vary?

Back 439

A lot! 1-110% of filtered load, depending upon dietary intake, aldosterone levels, and acid-base status

Front 440

What is splay?

Back 440

Splay is the difference between threshold and transport maximum (Tm).

Front 441

Causes of Hypokalemia?

Back 441

insulin
B-adrenergic agonists
alkalosis
hypoosmolarity

Front 442

K+ reabsorption
- PCT (1)
- TAL of henle (2)
- a-intercalated cells (3)

Back 442

1 = 67%
2 = 20% (Na+ K+ 2Cl- cotransporter)
3 = H+K+ ATPase

Front 443

How much K is reabsorbed in the proximal tubule?

Back 443

67%

Front 444

What are some causes of glucosuria?

Back 444

- In diabetes mellitus, the filtered load of glucose exceeds the reabsorptive capacity (plasma [glucose] is above Tm)

- During pregnancy, GFR is increased, which increases the filtered load of glucose to the extent that it may exceed the reabsorptive capacity.

- Congenital abnormalities of the Na+-glucose cotransporter lead to decreases in Tm.

Front 445

K+ reabsorption
- PCT (1)
- TAL of henle (2)
- a-intercalated cells (3)

Back 445

1 = 67%
2 = 20% (Na+ K+ 2Cl- cotransporter)
3 = H+K+ ATPase

Front 446

K+ secretion occurs in (1) and is mediated by what transporter? (2)

Back 446

1 = principal cells of distal tubule
2 = passively secreted down electrochemical gradient

Front 447

How much K is reabsorbed in the thick ascending limb of the loop of Henle?

Back 447

20%

Front 448

How is urea reabsorbed?

Back 448

Urea is reabsorbed by simple diffusion, in most segments of the nephron.

Front 449

Causes of Increased Distal K+ secretion? (6)

Back 449

high K+ diet
hyperaldosteronism
alkalosis
thiazide diuretics
loop diuretics
luminal anions

Front 450

K+ secretion occurs in (1) and is mediated by what transporter? (2)

Back 450

1 = principal cells of distal tubule
2 = passively secreted down electrochemical gradient

Front 451

How is K reabsorbed in the thick ascending limb of the loop of Henle?

Back 451

The Na-K-2Cl cotransporter

Front 452

What percentage of PAH is filtered across the glomerular capillaries?

Back 452

<10%. Ninety percent of the PAH in blood is bound to plasma proteins. Only the unbound portion is filterable. The filtered load increases linearly as the unbound concentration of PAH increases.

Front 453

Causes of Decreased Distal K+ secretion? (4)

Back 453

low K+ diet
acidosis
hypoaldosteronism
K+ sparing diuretics

Front 454

How do the distal tubule and collecting duct handle K transport?

Back 454

They either reabsorb OR secrete it, depending upon dietary intake

Front 455

Causes of Increased Distal K+ secretion? (6)

Back 455

high K+ diet
hyperaldosteronism
alkalosis
thiazide diuretics
loop diuretics
luminal anions

Front 456

What happens when PAH carriers reach Tm?

Back 456

When Tm is reached, there can be no further increase in the secretion rate of PAH.

Front 457

How is K reabsorbed in the distal tubule and collecting duct?

Back 457

H-K ATPase in the apical membrane of alpha intercalated cells

Front 458

Causes of Decreased Distal K+ secretion? (4)

Back 458

low K+ diet
acidosis
hypoaldosteronism
K+ sparing diuretics

Front 459

What drug uses the PAH transporter for secretion?

Back 459

Penicillin.

Front 460

Under what conditions is K reabsorbed in the distal tubule and collecting duct?

Back 460

Low K diet (K depletion). It is under these conditions that K excretion is 1% of filtered load

Front 461

Where and what percent is urea absorbed?

Back 461

50% of urea is reabsorbed in the proximal tubule

Front 462

At what urine pH does the HA form of a weak acid predominate?
Why is there more "back-diffusion" from urine into blood at this ph?

Back 462

At acidic urine pH.

There is more "back-diffusion" from urine into blood because the uncharged HA form can diffuse across the cells. The A- form of a weak acid cannot diffuse.

Front 463

How is K secreted in the distal tubule?

Back 463

The Na-K ATPase imports K into the cell across the basolateral membrane
K channels export K across the apical membrane into the lumen

Front 464

ADH increases the permeability to urea in (1)

Back 464

inner medullary collecting ducts

Front 465

At what urine pH does the A- form of a weak acid predominate?

Back 465

At alkaline urine pH.

There is less "back-diffusion" from urine to blood, and excretion of the acid is increased.

Front 466

What drives K transport in the distal tubule?

Back 466

Chemical and electrical driving forces
Things that increase intracellular K (or decrease luminal K) will increase the driving force for K secretion

Front 467

low urine flow rate, (1) urea reabsorption and (2) urea excretion; high urine flow rate, (3) urea reabsorption and (4) urea excretion

Back 467

1 = greater
2 = decreased
3 = decreased
4 = increased

Front 468

What does [TF/P]x = 1.0 indicate?

Back 468

The [TF/P]x ratio compares the concentration of a substance in tubular fluid to its concentration in systemic plasma.

When [TF/P]x = 1.0, it means that the concentrations are equal. This can mean a few things:
- The ratio was measured in Bowman's space for a freely filtered substance (and no reabsorption or secretion occurred yet)
- Reabsorption of the solute has occurred, but reabsorption of water has occurred in exactly the same proportion.

Front 469

What specific things increase distal K secretion?

Back 469

High dietary K (increases intracellular K)
Aldosterone (stimulation of the Na-K ATPase)
Alkalosis
Thiazide and loop diuretics
Luminal anions

Front 470

where is phosphate reabsorbed? (1)
- how much of it is reabsorbed? (2)
- transporter? (3)

Back 470

1 = proximal tubule
2 = 85%
3 = Na+ phosphate cotransport

Front 471

What does [TF/P]x < 1.0 indicate?

Back 471

The reabsorption of the solute must have been greater than reabsorption of water.

Front 472

What affect does hyperaldosteronism have upon K secretion?

Back 472

It increases K secretion and causes hypokalemia

Front 473

What hormone inhibits phosphate reabsorption?

Back 473

PTH
- causes phosphaturia and increased urinary cAMP

Front 474

What does [TF/P]x > 1.0 indicate?

Back 474

There are two possible meanings:
- There has been a net reabsorption of the solute, but solute reabsorption has been less than water reabsorption.
- There has been a net secretion of the solute into tubular fluid.

Front 475

What affect does hypoaldosteronism have upon K secretion?

Back 475

It decreases K secretion and causes hyperkalemia. The Na-K ATPase is no longer stimulated to remove K from the interstitium.

Front 476

Which diuretics increase Ca2+ excretion (1) and which decrease Ca2+ excretion (2)?

Back 476

1 = loop diuretics (furosemide)
2 = thiazide diuretics

Front 477

How can water reabsorption be calculated?

Back 477

Water reabsorption can be calculated from the value of [TF/P]inulin.

Front 478

What effect does pH have upon K secretion?

Back 478

Alkalosis increases K secretion
Acidosis decreases K secretion
H and K are effectively exchanged for each other across the basolateral membrane, so if the blood has excess H (acidosis), that H displaces K inside the cell such that K is no longer available for secretion

Front 479

Mg2+ and Ca2+ compete for reabsorption in the (1)

Back 479

1 = thick ascending limb

Front 480

What equation corrects for water reabsorption?
What would a value of 0.3 mean?

Back 480

[TF/P]x/[TF/P]inulin is a double ratio that corrects for water reabsorption.
A value of 0.3 means that 30% of the filtered load of the solute remains in the tubular fluid, or 70% has been reabsorbed.

Front 481

How do thiazide and loop diuretics affect K secretion?

Back 481

They increase flow rate through the distal tubule, which dilutes the K concentration within the lumen and creates a driving force for K secretion

Front 482

presence of ADH (1) the size of corticopapillary osmotic gradient by stimulating reabsorption of (2) in (3)

Back 482

1 = increases
2 = NaCl
3 = thick ascending limb

Front 483

presence of ADH (1) the size of corticopapillary osmotic gradient by stimulating reabsorption of (2) in (3)

Back 483

1 = increases
2 = NaCl
3 = thick ascending limb

Front 484

The reabsorption of which ion is the most important? Why?

Back 484

The reabsorption of sodium (Na+) is the most importnat function the kidney has. Sodium is the major cation of the ECF compartment. The amount of Na+ in ECF determines the ECF volume, which in turn determines plasma volume, blood volume, and blood pressure.

Front 485

How do K-sparing diuretics affect K secretion?

Back 485

They decrease K secretion, and can cause hyperkalemia if not used in conjunction with thiazide or loop diuretics (which would reduce urinary K loss)

Front 486

osmolarity of final urine = (1)

Back 486

1200 mOsm/L

Front 487

osmolarity of final urine = (1)

Back 487

1200 mOsm/L

Front 488

What percentage of Na+ reabsorption occurs in the proximal convoluted tubule?

Back 488

67% (two-thirds) of the filtered load is reabsorbed. It is isosmotic reabsorption.

Front 489

How do luminal anions affect K secretion?

Back 489

Excess anions in the lumen increase the negativity of the lumen, which favors K secretion

Front 490

What area of nephron does urine get concentrated? (1)
- due to presence of (2) and (3)

Back 490

1 = collecting ducts
2 = ADH which increases H20 permeability AND corticopapillary gradient

Front 491

What area of nephron does urine get concentrated? (1)
- due to presence of (2) and (3)

Back 491

1 = collecting ducts
2 = ADH which increases H20 permeability AND corticopapillary gradient

Front 492

Which part of the nephron reabsorbs 25% of the filtered load of Na+?

Back 492

Thick ascending limb of the loop of Henle. This region is impermeable to water.

Front 493

Where in the nephron is urea reabsorbed?

Back 493

50% is passively reabsorbed in the proximal tubule
The rest is reabsorbed in the inner medullary collecting duct upon ADH stimulation

Front 494

corticopapillary osmotic gradient is (1) without ADH

Back 494

decreased

Front 495

corticopapillary osmotic gradient is (1) without ADH

Back 495

decreased

Front 496

Which portion of the nephron is responsible for Na+ balance?

Back 496

The late distal convoluted tubule and collecting ducts, which also reabsorb the final 3% of the filtered load.

Front 497

How does ADH affect urea reabsorption?

Back 497

It increases the permeability of the inner medullary collecting duct

Front 498

free water clearance

Back 498

estimates the ability to concentrate or dilute urine

Front 499

free water clearance

Back 499

estimates the ability to concentrate or dilute urine

Front 500

Which portion of the nephron does aldosterone act on?

Back 500

The late distal convoluted tubule and collecting ducts.

Front 501

How does urea contribute to the corticomedullary osmotic gradient?

Back 501

ADH causes urea to be reabsorbed from the collecting duct to the interstitium, which creates an osmotic gradient that increases as you go deeper into the medulla

Front 502

Positive C H20 (free water clearance)

Back 502

- low ADH (no ADH)
- urine is hypoosmotic to plasma
- high water intake, central diabetes insipidus, nephrogenic diabetes insipidus

Front 503

In the early proximal tubule, what is Na+ reabsorbed with?
In the late proximal tubule?

Back 503

In the early proximal tubule, Na+ is reabsorbed primarily with HCO3- and organic solutes such as glucose and amino acids.
In the late proximal tubule, Na+ is reabsorbed primarily with Cl-.

Front 504

How does urine flow rate affect urea excretion?

Back 504

At low flow rates, more urea is reabsorbed and less is excreted, whereas at high flow rates, urea tends to be excreted

Front 505

Negative C H20 (free water clearance)

Back 505

high ADH
- urine is hyperosmotic to plasma
- water deprivation or SIADH

Front 506

What are the cotransport mechanisms in the luminal membrane of the early proximal tubule?

Back 506

Na+-glucose (SGLT), Na+-amino acid, Na+-phosphate, Na+-lactate, and Na+-citrate.

Front 507

Where is phosphate reabsorbed (and how much)?

Back 507

Proximal tubule; 85%
The remaining 15% is excreted in the urine

Front 508

Ch20 = ZERO

Back 508

produced with loop diuretics
-> inhibit both dilution in TAL and production of corticopapillary osmotic gradient which prevents concentration in CD

Front 509

What is the countertransport or exchange mechanism in the luminal membrane of the early proximal tubule?

Back 509

Na+-H+ exchanger.

Front 510

How is phosphate reabsorbed in the proximal tubule?

Back 510

Na-phosphate cotransport

Front 511

volatile acid

Back 511

CO2
--> produced by aerobic metabolism of cells

Front 512

What two exchangers exist in the late proximal tubule?

Back 512

Na+-H+ exchanger and Cl-formate anion exchanger, driven by the high tubular fluid Cl- concentration.

Front 513

How does PTH affect phosphate reabsorption?

Back 513

It inhibits it by generating cAMP and inhibiting Na-phosphate cotransport. Since phosphate reabsorption is decreased, PTH causes phosphaturia

Front 514

non volatile acid

Back 514

aka. fixed acids
- sulfuric acid
- phosphoric acid
- ketoacids
- lactic acid
- salicylic acid

Front 515

If there is an increase in GFR (and therefore an increase in filtered load of Na+), how does the nephron maintain glomerulotubular balance?

Back 515

Glomerulotubular balance ensures that a constant fraction of the filtered load is reabsorbed by the proximal tubule. When the GFR is increased, there is more fluid filtered. This leads to an increase in πc (oncotic pressure of peritubular capillary), which leads to increased reabsorption.

Front 516

Where is Ca reabsorbed (and how much)?

Back 516

Proximal tubule and thick ascending limb of the loop of Henle (90%)

Front 517

major extracellular buffer

Back 517

HCO3-

Front 518

During infusion of isotonic NaCl (ECF volume expansion), what is the mechanism that maintains glomerulotubular balance?

Back 518

An increase in ECF volume decreases the plasma protein concentration, and increases the capillary hydrostatic pressure. Both of the changes in these forces lead to a decrease in fractional reabsorption of isosmotic fluid in the proximal tubule.

Front 519

How much of the plasma Ca is filtered across the glomerular membrane?

Back 519

60%

Front 520

minor extracellular buffer

Back 520

phosphate

Front 521

During diarrhea or vomiting (ECF volume contraction), what are two mechanisms that maintain glomerulotubular balance?

Back 521

- A decrease in ECF volume increases plasma protein concentration, and decreases the capillary hydrostatic pressure. This leads to an increase in fractional reabsorption of isosmotic fluid.
- Decrease in blood volume and arterial pressure activates the renin-angiotensin-aldosterone system. Angiotensin II stimulates Na+-H+ exchange in the proximal tubule, and thereby stimulates reabsorption of Na+, HCO3-, and water.

Front 522

How do loop diuretics (eg furosemide) affect Ca excretion?

Back 522

They increase urinary Ca excretion because Na and Ca reabsorption in the loop of Henle are linked. Therefore, if the volume lost by the diuretic is replaced, loop diuretics can be used to treat hypercalcemia

Front 523

most important urinary buffer

Back 523

phosphate

Front 524

What is the result of activation of renin-angiotensin system during ECF volume contraction?

Back 524

Because angiotensin II mechanism specifically stimulates HCO3- reabsorption (along with Na+ and water), ECF volume contraction causes contraction alkalosis (metabolic alkalosis secondary to volume contraction).

Front 525

How does PTH affect Ca transport?

Back 525

It increases reabsorption in the distal tubule

Front 526

intracellular buffers (2)

Back 526

organic phosphates
proteins

Front 527

What is the thin descending limb permeable to?

Back 527

The thin descending limb is permeable to water and small solutes such as NaCl and urea.

Front 528

How do thiazide diuretics affect Ca transport?

Back 528

They increase reabsorption in the distal tubule, so they can be used to treat hypercalciuria

Front 529

major intracellular buffer

Back 529

hemoglobin (deoxy is better than oxy)

Front 530

What is the thin ascending limb permeable/impermeable to?

Back 530

The thin ascending limb is permeable to NaCl and impermeable to water.

Front 531

Where in the nephron is Mg reabsorbed?

Back 531

Hahaha! Pretty much everywhere -- proximal tubule, thick ascending limb, distal tubule

Front 532

Where does reabsorption of filtered HCO3- occur?

Back 532

proximal tubule

Front 533

What percentage of filtered Na+ is reabsorbed by the thick ascending limb?

Back 533

25%, although the thick ascending limb (and distal tubule) are load-dependent (the more Na+ delivered, the more it reabsorbs).

Front 534

How do calcium imbalance disorders affect Mg transport?

Back 534

In the thick ascending limb, Mg and Ca compete for reabsorption, so if you are hypercalcemic, Mg reabsorption is inhibited and Mg is excreted (likewise, hypermagnesemia increases Ca excretion by inhibiting Ca reabsorption)

Front 535

increases in filtered load for HCO3- result in (1) rates of HCO3- reabsorption until person develops (2) and then HCO3- is (3)

Back 535

1 = increased
2 = metabolic alkalosis
3 = excreted

Front 536

What is the mechanism for reabsorption of Na+ in the thick ascending limb?

Back 536

The luminal membrane contains a Na+-K+-2Cl- cotransporter.

Front 537

What hormone is responsible for the production of concentrated urine?

Back 537

ADH

Front 538

increased PCO2 = (1) HCO3- reabsorption

- basis for renal compensation of (2)

Back 538

1 = increased
2 = respiratory acidosis

Front 539

Why is the Na-K-2Cl cotransporter considered electrogenic? What happens because of this?

Back 539

The cotransporter transports all three ions (Na, K, and Cl) into the cell of the thick ascending limb; Na is extruded from the cell by the Na-K ATPase, and Cl and K diffuse through channels in the basolateral membrane.

A portion of the K, however, diffuses back into the lumen. Thus, the cotransporter brings slightly more negative than positive charge into the cell. This results in a lumen-positive potential difference across the cells of the thick ascending limb. This is the driving force for the reabsorption of divalent cations such as Ca and Mg.

Front 540

When is ADH produced?

Back 540

Water deprivation
Hemorrhage (depleted ECFV)
Increased plasma osmolarity

Front 541

ECF volume expansion = (1) HCO3- reabsorption
ECF volume contraction = (2) HCO3- reabsorption

Back 541

1 = decreased
2 = increased

Front 542

How do the loop diuretics work?

Back 542

Look diuretics are organic acids that are related to PAH. At physiologic pH, the loop diuretics are anions that attach to the Cl- binding site of the Na-K-2Cl cotransporter.

Front 543

What hormone is responsible for the generation of the corticomedullary osmotic gradient?

Back 543

ADH

Front 544

angiotensin II stimulates (1) and thus (2) HCO3- reabsorption which contributes to (3) seen with ECF volume contraction

Back 544

1 = Na+ H+ exchange
2 = increases
3 = contraction alkalosis

Front 545

What is the [TF/P]na and [TF/P]osm for the fluid that leaves the thick ascending limb?

Back 545

[TF/P]na < 1.0
[TF/P]osm < 1.0

Front 546

What is the corticomedullary osmotic gradient?

Back 546

As you go from the cortex to the medulla, the osmolarity increases from 300 mOsm/L to 1200 mOsm/L. It is established by countercurrent multiplication and urea recycling, and is maintained by countercurrent exchange in the vasa recta

Front 547

aldosterone increases (1) on PT luminal mb which increases (2) of H+ and reabsorption of (3)

Back 547

1 = H+ ATPase
2 = secretion
3 = reabsorption of HCO3-

Front 548

What is the mechanism of reabsorption of filtered Na in the early distal tubule?

Back 548

The mechanism is an Na-Cl cotransporter in the luminal membrane.

Front 549

What compounds create the corticomedullary osmotic gradient?

Back 549

NaCl and urea

Front 550

amount of H+ excreted as NH4+ depends on (1) and (2)

Back 550

1 = amount of NH3 synthesized by renal cells
2 = urine pH

Front 551

How do thiazide diuretics work?

Back 551

The thiazides are organic acids, which are anions at physiologic pH. They bind to the Cl site of the Na-Cl cotransporter and prevent it from cycling.

Front 552

How does ADH affect NaCl reabsorption?

Back 552

It increases reabsorption in the thick ascending limb of the loop of Henle, which augments the corticomedullary osmotic gradient

Front 553

hyperkalemia (1) NH3 synthesis resulting in (2) H+ excretion as NH4+

Back 553

1 = inhibits
2 = decreased

Front 554

What are the two major cell types of the late distal tubule and collecting duct? What do they do?

Back 554

Principal cells are involved in Na reabsorption, K secretion, and water reabsorption.
α-Intercalated cells are involved in K reabsorption and H secretion.

Front 555

What role do the vasa recta play in the corticomedullary osmotic gradient?

Back 555

They act as osmotic exchangers, meaning they osmotically equilibrate with the interstitial fluid of the medulla

Front 556

metabolic acidosis
- increase in arterial (1)
- decrease in arterial (2) (buffer)
- respiratory compensation is (3)

Back 556

1 = H+ conc.
2 = HCO3- conc.
3 = hyperventilation

Front 557

What is the mechanism of Na reabsorption in the principal cells?

Back 557

The luminal membrane of the principal cells contain Na channels, through which Na diffuses down its electrochemical gradient.

Front 558

How does ADH rectify water deprivation?

Back 558

Water deprivation
Increased plasma osmolarity
Stimulation of hypothalamus osmoreceptors
Secretion of ADH from anterior pituitary
Increased water permeability of late distal tubule and collecting duct
Increased water reabsorption
Increased urine concentration
Decreased plasma osmolarity

Front 559

compensation of metabolic acidosis
- increased excretion of (1)
- increased reabsorption of (2)
- adaptive increase in (3)

Back 559

1 = H+ as titratable acid and NH4+
2 = HCO3-
3 = NH3 synthesis

Front 560

What does aldosterone do to increase the reabsorption of Na?

Back 560

The steroid hormone, which is able to diffuse into the cell and is transferred to the nucleus, directs the synthesis of specific mRNAs. These mRNAs then direct the synthesis of new proteins that are involved in Na reabsorption by the principal cells, which include the Na channel itself, Na-K ATPase, and enzymes of the citric acid cycle.

Front 561

How does the osmolarity of glomerular filtrate compare to that of plasma?

Back 561

They are equal (300 mOsm/L)

Front 562

serum anion gap

Back 562

[Na+] - ( [Cl-] + [HCO3-] )

represents unmeasured anions in serum including phosphate, citrate, sulfate and protein

Front 563

What are the renal mechanisms that regulate Na excretion?

Back 563

Sympathetic nerve activity
Atriopeptin (ANP)
Starling forces in peritubular capillaries
Renin-angiotensin-aldosterone system

Front 564

What is the TF/Posm along the length of the nephron?

Back 564

Proximal tubule: 1
Thick ascending limb: < 1 (because of dilution)
Late distal tubule: 1
Collecting duct: > 1 in the presence of ADH (because of water reabsorption), < 1 in the absence of ADH

Front 565

normal value of serum anion gap

Back 565

12mEq/L

Front 566

How does Sympathetic nerve activity regulate Na balance/excretion?

Back 566

Sympathetic activity is activated by the baroreceptor mechanism in response to a decrease in arterial pressure. It causes vasoconstriction of afferent arterioles and increased proximal tubule Na reabsorption.

Front 567

What is the water permeability in the various segments of the nephron?

Back 567

Proximal tubule: permeable
Thick ascending limb: impermeable
Early distal tubule: impermeable
Late distal tubule: permeable in response to ADH
Collecting duct: permeable in response to ADH

Front 568

serum anion gap is (1) if the conc. of an unmeasured anion is (2) to replace HCO3-

Back 568

1 = increased
2 = increased

Front 569

How does atriopeptin (ANP) regulate Na excretion?

Back 569

ANP is secreted by the atria in response to an increase in ECF volume. It causes vasodilation of afferent arterioles, vasoconstriction of efferent arterioles, increased GFR, and decreased Na reabsorption in the late distal tubule and collecting ducts.

Front 570

How does ADH alter the magnitude of the corticomedullary osmotic gradient?

Back 570

Increases it

Front 571

serum anion gap is (1) if the conc. of Cl- is (2) to replace HCO3-

Back 571

1 = normal
2 = increased

aka. hyperchloremic metabolic acidosis

Front 572

How does the renin-angiotensin-aldosterone system regulate Na excretion?

Back 572

The system is activated in response to decreased arterial pressure. Angiotensin II stimulates Na reabsorption in the proximal tubule, and aldosterone stimulates Na reabsorption in the late distal tubule and collecting ducts.

Front 573

What is free-water clearance (Ch2o)?

Back 573

It is used to estimate the kidney's ability to concentrate or dilute the urine. Free water is the solute-free water produced in the diluting segments where NaCl is reabsorbed and water is left behind in the lumen

Front 574

metabolic alkalosis
- decrease in arterial (1)
- increase in arterial (2)
- respiratory compensation with (3)

Back 574

1 = H+ conc.
2 = HCO3- conc.
3 = hypoventilation

Front 575

What are 5 things that cause K to shift into cells, and cause hypokalemia?

Back 575

Insulin
α-Adrenergic antagonists
β2-Adrenergic agonists
Alkalosis
Hyposmolarity

Front 576

How does ADH affect the sign of Ch2o?

Back 576

In the absence of ADH, Ch2o is POSITIVE (solute-free water is excreted)
In the presence of ADH, Ch2o is NEGATIVE (solute-free water is reabsorbed in the late distal tubule and collecting duct)

Front 577

What happens when metabolic alkalosis is accompanied by ECF volume contraction?

Back 577

reabsorption of HCO3- increases, worsening the metabolic alkalosis (contraction alkalosis)

Front 578

What are 7 things that cause K to shift out of cells, and cause hyperkalemia?

Back 578

Insulin deficiency
α-Adrenergic agonists
β2-Adrenergic antagonists
Acidosis
Hyperosmolarity
Cell lysis
Exercise

Front 579

What is the formula for Ch2o?

Back 579

Ch2o = urine flow rate x osmolar clearance

Front 580

respiratory acidosis
- caused by (1)
- increased arterial (2)
- increased arterial (3) and (4)

Back 580

1 = decrease in respiratory rate and retention of CO2
2 = PCO2
3 = H+ and HCO3-

Front 581

How does insulin stimulate K uptake into cells?

Back 581

Insulin increases the activity of Na-K ATPase.

Front 582

What does it mean when Ch2o is equal to 0?

Back 582

Urine is isosmotic (isosthenuric) to plasma

Front 583

compensation for respiratory acidosis
- respiratory comp (1)?
- renal comp (2)

Back 583

1 = no respiratory compensation
2 = increased excretion of H+ and increased reabsorption of HCO3-

Front 584

What happens to the K balance during alkalemia? Acidemia?

Back 584

In alkalemia, the H+ concentration is decreased: H+ leaves the cells and K+ enters the cells, producing hypokalemia.
In acidemia, H+ concentration in blood is increased: H+ enters the cells and K+ leaves the cells, producing hyperkalemia.

Front 585

How do loop diuretics contribute to a Ch2o of 0?

Back 585

They inhibit NaCl reabsorption in the thick ascending limb and abolish the corticomedullary osmotic gradient. Therefore, urine cannot be diluted (because the diluting segment is inhibited) or concentrated (because there is no longer an osmotic gradient)

Front 586

respiratory alkalosis
- caused by (1)
- decreased arterial (2)
- decreased arterial (3) and (4)

Back 586

1 = increase in respiratory rate and loss of CO2
2 = PCO2
3 = H+ and HCO3-

Front 587

Why is there generally no K+ shift during respiratory acidosis or respiratory alkalosis?

Back 587

Because these conditions are caused by a primary disturbance of CO2. CO2 is lipid soluble, so it freely crosses cell membranes and needs no exchange with K+ to preserve electroneutrality.

Front 588

What does it mean when Ch2o is positive?

Back 588

Urine is hyposmotic to plasma (low ADH conditions)
This occurs during high water intake (supressed ADH release) and during central and nephrogenic diabetes insipidus (inadequate response to ADH)

Front 589

compensation for respiratory alkalosis
- respiratory comp?
- renal comp?

Back 589

1 = no respiratory compensation
2 = decreased excretion of H+ and decreased reabsorption of HCO3-

Front 590

When would metabolic acidosis not cause a K+ shift?

Back 590

When the metabolic acidosis is caused by an excess of an organic acid (i.e. lactic acid, ketoacids, or salicylic acid).

Front 591

What does it mean when Ch2o is negative?

Back 591

Urine is hyperosmotic to plasma (high ADH conditions)
This happens when you are water-deprived (stimulates ADH release) or overproduce ADH (SIADH)

Front 592

What are the effects of activating adrenergic receptors?

Back 592

Activation of β2-adrenergic receptors by β2-agonists (i.e. albuterol) increases the activity of the Na-K ATPase, causing a shift of K into the cells, and possibly producing hypokalemia.

α-Adrenergic receptor activation causes a shift out of cells, and may produce hyperkalemia.

Front 593

What stimulates PTH secretion?

Back 593

Decreased plasma Ca

Front 594

Which cells reabsorb K in the distal tubule and collecting ducts? Which cells secrete K?
What are the mechanisms of the reabsorption and secretion?

Back 594

α-Intercalated cells reabsorb K through H-K ATPases in the luminal membrane.
Principal cells secrete K via Na-K ATPase and K channels.

Front 595

What effect does PTH have upon the kidney?

Back 595

Decreases phosphate reabsorption in the proximal tubule
Increases Ca reabsorption in the distal tubule

Front 596

What are the three effects that aldosterone has on the secretion of K+?

Back 596

1. Aldosterone induces the synthesis of more luminal membrane Na channels.
2. Aldosterone increases the quantity of Na-K ATPase
3. Aldosterone increases the number of K+ channels in the luminal membrane.

Front 597

What stimulates ADH secretion?

Back 597

Increased plasma osmolarity
Decreased blood volume

Front 598

How and where is phosphate reabsorbed?

Back 598

70% of the filtered load is reabsorbed in the proximal convoluted tubule. 15% is reabsorbed in the proximal straight tubule (right before loop of henle). 15% of the filtered load of phosphate is excreted.

Phosphate reabsorption is accomplished by an Na-phosphate cotransporter in the luminal membrane of the proximal tubule cells.

Front 599

What effect does ADH have upon the kidney?

Back 599

Increases water permeability of the late distal tubule and collecting duct

Front 600

How does PTH regulate phosphate excretion?

Back 600

PTH inhibits the Na-phosphate cotransporter.

Front 601

What stimulates aldosterone secretion?

Back 601

Decreased blood volume (via the RAS)
Increased plasma K

Front 602

How is Ca reabsorbed in the thick ascending limb?

Back 602

Like Na, 25% of the filtered load of Ca is reabsorbed in the thick ascending limb. Due to the lumen-positive potential difference, Ca is reabsorbed in a paracellular route (between cells).

Front 603

What effect does aldosterone have upon the kidney?

Back 603

Increased Na reabsorption in the distal tubule principal cells
Increased K secretion in the distal tubule principal cells
Increased H secretion in the alpha intercalated cells

Front 604

Where is magnesium reabsorbed the most in the nephron?

Back 604

Mg2+ is reabsorbed most in the thick ascending limb, where 60% of the filtered load is reabsorbed, in comparison to the proximal tubule, which only reabsorbs 30%.

Front 605

What stimulates ANP release?

Back 605

Increased atrial pressure

Front 606

What is the two step process of countercurrent multiplication?

Back 606

The single effect, the first step, refers to the function of the thick ascending limb. In the TAL, NaCl is reabsorbed via the Na-K-2Cl cotransporter. Due to the permeabilities of the loop of Henle, the result of the single effect is to decrease the osmolarity of the ascending limb, and increase the osmolarities of the interstitial fluid and descending limb.

The second step is the flow of tubular fluid. Fluid continuously flows through the nephron, and the new fluid that enters the descending limb will have an osmolarity of 300 mOsm/L. The high osmolarity fluid in the descending limb (created by the single effect) is pushed down toward the bend of the loop of Henle.

Front 607

What effect does ANP have upon the kidneys?

Back 607

Increases GFR
Decreases Na reabsorption

Front 608

What are the steps of urea recycling? Where does it occur?

Back 608

Urea recycling occurs in the inner medulla.
1. In the cortical and outer medullary collecting ducts, ADH increases water permeability, but not for urea. Water is reabsorbed, urea remains behind.

2. Urea concentration increases.

3. In the inner medullary collecting ducts, ADH increases both water and urea permeability.

4. Urea diffuses down its concentration gradient into the interstitial fluid in the inner medulla, where it is added to the corticopapillary osmotic gradient.

Front 609

What stimulates angiotensin II production?

Back 609

Decreased blood volume (via renin)

Front 610

What is the difference between countercurrent multiplication and countercurrent exchange?

Back 610

Countercurrent multiplication is an active process that establishes the corticopapillary osmotic gradient. Countercurrent exchange is a purely passive process that helps maintain the gradient.

Front 611

What effect does angiotensin II have upon the kidneys?

Back 611

Increased Na reabsorption
Increased HCO3 reabsorption

Front 612

What are the three effects of ADH on the renal tubule?

Back 612

1) increases the water permeability of the principal cells of the late distal tubule and collecting ducts
2) increases the activity of the Na-K-2Cl cotransporter of the thick ascending limb
3) increases urea permeability in the inner medullary collecting ducts.

Front 613

What types of acids are produced by the body?

Back 613

Volatile (CO2) and non-volatile acids

Front 614

What are the receptors for ADH? What type of protein regulates the action of ADH?

Back 614

V2 receptors for ADH on the principal cells.
Gs protein.

Front 615

How are volatile acids produced?

Back 615

Carbonic anhydrase catalyzes the reversible reaction of H and HCO3 to give CO2 and water

Front 616

What is the water channel controlled by ADH?

Back 616

Aquaporin 2 (AQP2)

Front 617

What non-volatile acids are produced, and is this normal or pathological?

Back 617

Normal: sulfuric, phosphoric acid
Bad: ketoacids, lactic acid, salicylic acid

Front 618

What do you use to treat SIADH?

Back 618

Demeclocycline, which inhibits the ADH action on the renal principal cells.

Front 619

What are buffers?

Back 619

The prevent a change in pH when H+ is added or removed from solution. They are most effective when they are within 1.0 pH unit of the pK of the buffer (within the linear portion of the titration curve)

Front 620

What do you use to treat central diabetes insipidus? Nephrogenic diabetes insipidus?

Back 620

In central DI, treatment consists of administration of an ADH analogue, such as 1-deamino-8-D-arginine vasopressin (dDAVP).

In nephrogenic DI, treatment consists of thiazide diuretics. Thiazide diuretics inhibit Na-Cl cotransport in the early distal tubule, preventing dilution of the urine in this segment. As more NaCl is excreted, the urine is less dilute than it would be without treatment. Thiazide diuretics also produce a decrease in GFR and decrease in ECF volume. The decrease in ECF volume causes an increase in proximal tubule reabsorption via effects on Starling forces. The combination of less water filtered and more water reabsorbed in the proximal tubule means that the total volume of water excreted is decreased.

Front 621

What is the major physiological buffer?

Back 621

HCO3/CO2. The pK of the buffer pair is 6.1

Front 622

What does it mean when free water clearance (CH2O) is zero? When does this occur?

Back 622

When free water clearance = 0, no solute-free water is excreted. Urine is isosmotic with plasma (isosthenuric). This can occur during treatment with a loop diuretic, where NaCl reabsorption is inhibited in the thick ascending limb.

Front 623

What role does phosphate play as a buffer?

Back 623

It is a minor extracellular buffer, and the pK of H2PO4/HPO4 is 6.8. It is an important urinary buffer and as such contributes to the excretion of titratable acid

Front 624

What does it mean when free water clearance (CH2O) is positive? When does this occur?

Back 624

When CH2O is positive, free water is being excreted.
This occurs when ADH levels are low or ADH is ineffective and the urine is hyposmotic.

Front 625

What are some intracellular buffers?

Back 625

Organic phosphates (AMP, ADP, etc)
Proteins (hemoglobin, deoxyhemoglobin)

Front 626

What does it mean when free water clearance (CH2O) is negative? When does this occur?

Back 626

When CH2O is negative, free water is reabsorbed in the late distal tubule and collecting ducts.
This occurs when ADH levels are high and the urine is hyperosmotic.

Front 627

What is the overall Henderson-Hasselbalch equation?

Back 627

pH = pK + log [A-/HA]

Front 628

What does it mean when the pH of a solution equals the pK?

Back 628

The concentrations of HA and A- are equal

Front 629

Where does bicarbonate reabsorption occur?

Back 629

Primarily in the proximal tubule

Front 630

How is bicarbonate reabsorbed in the proximal tubule?

Back 630

H is secreted via the Na-H exchanger
Carbonic anhydrase catalyzes the reaction of that H with HCO3 in the lumen to give CO2 and water
CO2 and water go into the cell
Carbonic anhydrase converts them back to H and HCO3
The H is recycled into the lumen and the HCO3 is reabsorbed into the blood

Front 631

How does filtered load affect HCO3 reabsorption?

Back 631

It increases it until the reabsorptive capacity, at which point excess HCO3 will be excreted in the urine

Front 632

How does PCO2 affect HCO3 reabsorption?

Back 632

Increased PCO2 results in increased HCO3 reabsorption because there is more intracellular H available for secretion (this is the mechanism for renal compensation for respiratory acidosis)

Front 633

How does ECFV affect HCO3 reabsorption?

Back 633

ECFV expansion decreases HCO3

Front 634

How does angiotensin II affect bicarbonate reabsorption?

Back 634

It increases it by stimulating Na-H exchange

Front 635

How is acid excreted in the kidneys?

Back 635

It is excreted as titratable acid or NH4

Front 636

What is titratable acid?

Back 636

It is acid that is buffered by urinary buffers. To determine how much titratable acid there is, you titrate the urine with NaOH until you get to 7.4, and the amount of base you need to add is equal to the amount of titratable acid

Front 637

How does aldosterone increase H secretion?

Back 637

It stimulates the H ATPase

Front 638

What does the excretion of titratable acid represent?

Back 638

A net secretion of acid and a net reabsorption of HCO3

Front 639

What is the minimum urinary pH?

Back 639

4.4

Front 640

What determines the amount of H+ excreted as titratable acid?

Back 640

The amount of urinary buffer and the pK of the buffer

Front 641

What determines the amount of H+ excreted as NH4?

Back 641

The amount of NH3 synthesized by renal cells and urine pH

Front 642

How is NH3 produced in renal cells?

Back 642

Glutamine is converted to HCO3 and NH3

Front 643

How is NH4 produced in the urine?

Back 643

NH3 diffuses down its concentration gradient from the cells to the lumen
Secreted H+ reacts with it to form NH4
The NH4 is excreted; this is known as diffusion trapping

Front 644

How does pH affect the relative amount of NH4 in the urine?

Back 644

The lower the pH of the tubular fluid, the more H+ will be excreted as NH4. This is because during acidosis there is an adaptive increase in NH3 synthesis

Front 645

How does hyperkalemia inhibit H+ excretion as NH4?

Back 645

It inhibits the synthesis of NH3

Front 646

What is metabolic acidosis?

Back 646

Overproduction or ingestion of non-volatile acid, or loss of base

Front 647

Why does arterial HCO3 decrease in metabolic acidosis?

Back 647

It is used to buffer the excess acid

Front 648

What is the respiratory compensation for metabolic acidosis?

Back 648

Hyperventilation

Front 649

What is the renal response to metabolic acidosis?

Back 649

Increased excretion of H+ as titratable acid and NH4 (this is facilitated by an adaptive increase in NH3 synthesis)
Increased reabsorption of HCO3 (replenishes the HCO3 that is used to buffer excess H)

Front 650

What is the formula for the serum anion gap?

Back 650

Na - (Cl + HCO3)

Front 651

What does the serum anion gap represent?

Back 651

It represents unmeasured anions in the serum. The normal value is 12 mEq/L

Front 652

How does the serum anion gap change in metabolic acidosis?

Back 652

HCO3 is consumed in acidosis, so to maintain electroneutrality, the concentration of another anion must increase. The gap increases if the anion is unmeasured, and is normal if the anion is Cl

Front 653

What is metabolic alkalosis?

Back 653

Loss of non-volatile acid or gain of base

Front 654

How does vomiting contribute to metabolic alkalosis?

Back 654

H+ is lost from the stomach

Front 655

What is the respiratory compensation for metabolic alkalosis?

Back 655

Hypoventilation

Front 656

What is the renal response to metabolic alkalosis?

Back 656

Increased HCO3 excretion, because the filtered load of HCO3 exceeds the reabsorptive capacity

Front 657

What is contraction alkalosis?

Back 657

If metabolic alkalosis is accompanied by ECFV contraction (as in the case of vomiting), the RAS is activated, which promotes H secretion and exacerbates the alkalosis

Front 658

What is respiratory acidosis?

Back 658

Decreased respiration rate results in CO2 retention and elevates PCO2. Elevated CO2 results in an increase in H and HCO3

Front 659

What is the respiratory compensation for respiratory acidosis and alkalosis?

Back 659

NONE!!!! hahahahaha

Front 660

What is the renal response to respiratory acidosis?

Back 660

Increased H excretion as titratable and NH4
Increased reabsorption of HCO3
This is facilitated by the increased PCO2, which provides more H to the renal cells for secretion

Front 661

What is the difference between acute and chronic respiratory acidosis? (note that this is also the case with respiratory alkalosis)

Back 661

In acute, renal compensation hasn't occurred yet, so the pH is more acidic

Front 662

What is respiratory alkalosis?

Back 662

Increased respiration rate results in loss of CO2. This results in decreased production of H and HCO3

Front 663

What is the renal response to respiratory alkalosis?

Back 663

Decreased H+ excretion
Increased HCO3 reabsorption
This is aided by the low PCO2, which decreases the availability of H in the renal cells for secretion

Front 664

Why is hypocalcemia a symptom of respiratory alkalosis?

Back 664

H and Ca compete for binding sites on plasma proteins, so if there isn't enough H, more Ca will bind to proteins, which decreases free ionized Ca

Front 665

What are the effects of hypoaldosteronism on the kidney?

Back 665

Decreased Na reabsorption
Decreased K and H secretion
This results in ECFV contraction, hyperkalemia, and metabolic acidosis

Front 666

Why do patients with hypoaldosteronism have orthostatic hypotension?

Back 666

There is an ECFV contraction, and the decreased arterial pressure produces an increased pulse pressure

Front 667

Why is ADH secreted in hypoaldosteronism?

Back 667

There is an ECF volume contraction

Front 668

How does hypoaldosteronism cause hyperpigmentation?

Back 668

Adrenal insufficiency decreases the production of cortisol, which increases secretion of ACTH, which has pigmenting effects

Front 669

How does vomiting cause metabolic alkalosis?

Back 669

H+ is lost
Cl is also lost, resulting in hypochloremia and ECF volume contraction

Front 670

Why is aldosterone secretion increased during vomiting?

Back 670

There is an ECF volume contraction, which results in decreased renal perfusion pressure. This causes renin secretion, which activates the RAS

Front 671

Why is hypokalemia observed during vomiting?

Back 671

Increased aldosterone secondary to ECFV contraction promotes K secretion

Front 672

How is vomiting treated?

Back 672

NaCl infusion to correct the ECF volume contraction
Administration of K to replace urinary K loss

Front 673

How does diarrhea cause metabolic acidosis?

Back 673

You lose bicarbonate

Front 674

Why is the anion gap normal in diarrhea?

Back 674

To maintain electroneutrality, the HCO3 that is lost is replaced by increased Cl

Front 675

Why is pulse rate increased in diarrhea?

Back 675

There is an ECF volume contraction, which decreases blood volume and arterial pressure. This decreased pressure activates the baroreceptor reflex, which increases heart rate via sympathetic stimulation to the SA node

Front 676

Why does diarrhea result in hypokalemia?

Back 676

ECF volume contraction activates the RAS, and the aldosterone increases distal K secretion
K is also lost in the diarrhea fluid

Front 677

How is diarrhea treated?

Back 677

Replacement of fluid and electrolytes

Front 678

Approximately, how much of your body weight is water?

Back 678

60%
This is known as total body water (TBW)

Front 679

What sort of people have the highest percent TBW?

Back 679

Newborns
Adult males

Front 680

What sort of people have the lowest percent TBW?

Back 680

Adult females
People with lots of adipose tissue

Front 681

What are the two compartments of the TBW?

Back 681

Intracellular fluid (ICF) -- 2/3 of TBW
Extracellular fluid (ECF) -- 1/3 of TBW

Front 682

What are the major cations of the ICF?

Back 682

K and Mg

Front 683

What are the major anions of the ICF?

Back 683

Protein
Organic phosphates (ATP, ADP, AMP)

Front 684

What are the two compartments of the ECF?

Back 684

Interstitial fluid -- 3/4 of ECF
Plasma -- 1/4 of ECF

Front 685

What is the major cation of the ECF?

Back 685

Na

Front 686

What are the major anions of the ECF?

Back 686

Cl
HCO3

Front 687

What are Prions? What are they resistant to?

Back 687

-misfolded proteins make others misfold, accumulate in brain tissue
-boiling, baking, radiation, disinfectants

Front 688

What is the 60-40-20 rule?

Back 688

TBW is 60% of body weight
ICF is 40% of body weight
ECF is 20% of body weight

Front 689

What is the dilution method?

Back 689

A known about of indicator is administered
This indicator must distribute throughout the compartment of interest
The substance equilibrates
The concentration of the substance is measured
Volume = amount / concentration

Front 690

What are indicators for TBW?

Back 690

Tritiated H2O
D2O

Front 691

What are indicators for ECF?

Back 691

Sulfate
Inulin
Mannitol

Front 692

What are indicators for plasma?

Back 692

RISA
Evan's blue

Front 693

What is a marker for interstitial fluid?

Back 693

There is no real marker
ECF - plasma volume (indirect calculation)

Front 694

What is a marker for ICF?

Back 694

There is no real marker
TBW - ECF (indirect calculation)

Front 695

How do ECF and ICF osmolarity compare at steady state?

Back 695

They are equal
To achieve this, water shifts between the compartments
It is assumed that osmotically active solutes like NaCl don't cross the cell membranes

Front 696

What type of volume change is observed when you infuse isotonic NaCl?

Back 696

Isosmotic fluid expansion

Front 697

What characterizes an isosomotic fluid expansion?

Back 697

ECF volume increases
ECF osmolarity stays the same
No water shifts to the ICF
Plasma protein concentration and hematocrit decrease because you are diluting the blood
RBCs do not shrink or swell
Arterial blood pressure increases

Front 698

What type of volume change is observed when you have diarrhea?

Back 698

Isosmotic volume contraction

Front 699

What characterizes an isosmotic volume contraction?

Back 699

ECF volume decreases
ECF osmolarity doesn't change
No water shift
Plasma protein concentration and hematocrit increase
RBCs do not shrink or swell
Arterial blood pressure decreases

Front 700

What type of volume change is observed when you have excessive NaCl intake?

Back 700

Hyperosmotic volume expansion

Front 701

What characterizes a hyperosmotic volume expansion?

Back 701

ECF osmolarity increases
Water shifts from ICF to ECF until ICF and ECF osmolarity are equal
ECF volume increases, ICF volume decreases
Plasma protein concentration and hematocrit decrease

Front 702

What type of volume change is observed when you sweat out a lot of water?

Back 702

Hyperosmotic volume contraction

Front 703

What characterizes a hyperosmotic volume contraction?

Back 703

The osmolarity of the ECF increases because sweat is hyposmotic
ECF volume decreases
Water shifts from ICF to ECF until the osmolarities are equal
Plasma protein concenration increases
Hematocrit does not change because water shifts out of the RBCs and decreases their volume

Front 704

What type of volume change is observed when you have SIADH (syndrome of inappropriate antidiuretic hormone)?

Back 704

Hyposmotic volume expansion

Front 705

What characterizes a hyposmotic volume expansion?

Back 705

The osmolarity of ECF decreases because excess water is retained
ECF volume increases
Water shifts from ECF to ICF
Plasma protein concentration decreases
Hematocrit stays the same because water shifts into the RBCs

Front 706

What type of volume change is observed when you have adrenocortical insufficiency and lose a lot of NaCl (not enough aldosterone)?

Back 706

Hyposmotic volume contraction

Front 707

What characterizes a hyposmotic volume contraction?

Back 707

The osmolarity of the ECF decreases
ECF volume decreases
Water shifts from ECF to ICF
Plasma protein concentration and hematocrit increase
Arterial blood pressure decreases