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AIM 2.2 > Renal Physio > Flashcards

Renal Physio Flashcards

1
Q

how does kidney accomplish its homeostatic role?

A

1) filter blood to generate fluid in renal tubule free of cells/proteins.
2) reabsorbs solutes and water from tubular fluid
3) secretes other solutes (uric acid) into tubular fluid
4) excretes tubular fluid (urine)

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2
Q

specific renal functions

A

1) regulation of body fluid volume
2) regulation of BP and volume
3) regulation of concentration of plasma electrolytes
4) regulation of plasma pH
5) elimination of waste products from metabolism (ex: urea from protein, uric acid from nucleic acids)
5) removal of drugs and foreign compounds from circulation
6) synthesis of certain hormones (renin, erythropoeitin)

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3
Q

urine drains from ______ that form renal pyramid into _______ and then into _______.

A

urine drains from RENAL PAPILLAE that form renal pyramid into RENAL CALYX and then into PELVIS.

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4
Q

kidneys receive __% of cardiac output

A

kidneys receive 25% of cardiac output

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5
Q

osmolarity of cortex vs of medulla

A

Cortex (outer area): 300 mOsm – ~same as plasma

Medulla (inner area): 1200 mOsm (4x higher to better concentrate the urine

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6
Q

where in the nephron is 2/3 of the water and sodium reabsorbed?

A

proximal tubule

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7
Q

blood enters glomerulus via ______, and exits via ___________

A

blood enters glomerulus via afferent arteriole, and exits via efferent arteriole

(NOT a venule)

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8
Q

thin descending tubule

A

Very permeable to water.

Water leaves due to increasing concentration gradient.

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9
Q

thin ascending tubule

A

Impermeable to water.

Na+ reabsorption (Na concentration decreases in cortex as tube ascends, so Na+ leaves tubule)

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10
Q

thick ascending tubule

A

Impermeable to water.
Na+ reabsorbed.
TRANSPORTER:

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11
Q

juxtaglomerular apparatus (general and components)

A

Distal tubule in v close proximity to glomerulus.

Macula densa and juxtaglomerular cells

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12
Q

macula densa

A

Senses concentration of solute in fluid flow (mainly Na conc)

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13
Q

juxtaglomerular cells

A

Sense fluid flow.

Produces renin to control constriction of afferent/efferent arterioles

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14
Q

processes involved in urine formation

A

1) glomerular filtration
2) tubular reabsorption
3) tubular secretion
4) excretion

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15
Q

formula for urine excretion

A

excretion = filtration - reabsorption + secretion

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16
Q

Substances that are reabsorbed reenter circulation via _______

A

peritubular capillaries

this is from efferent arterioles

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17
Q

layers of the capillary membrane

A

1) capillary endothelial cells (fenestrated)
2) basement membrane
3) podocytes (form filtration slits)

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18
Q

how does basement membrane prevent proteins from entering Bowman’s space?

A

1) negative charge causes electrostatic repulsion of proteins
2) has only small holes that can only allow water and sodium to pass

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19
Q

nephrin

A

Transmembrane protein embedded in podocyte membrane.

Covers filtration slits. But interdigitations of nephrins leave gaps, allowing fluid to flow through

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20
Q

mutation of nephrins

A

Causes loss of protein in urine.
Leads to edema, heart failure.

NEPHROTIC SYNDROME

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21
Q

GFR

A

Glomerular filtration rate.
The rate at which fluid is filtered thru the glomerulus.

Typical: 125 mL/min

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22
Q

RPF

A

Renal Plasma Flow.
Rate at which plasma is delivered to kidneys.

Typical: 650 mL/min

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23
Q

Filtration Fraction

A

GFR/RPF

Fraction of plasma entering the kidney which undergoes filtration across the glomerular capillary membrane.

Typical: 20%

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24
Q

glomerulonephritis

A

Renal disease initiated by an immune response.
Streptococcal infection causes antigen-antibody complexes to build up in glomerulus, damaging it.
DECREASES GFR.

Increases permeability/leakage, so proteins are lost (proteinuria)

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25
Q

kidney stones

A

Block flow of renal filtrate.
Increase hydrostatic pressure of Bowman’s Capsule.
DECREASES GFR

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26
Q

normal oncotic pressure of Bowman’s capsule

A

0

because no proteins

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27
Q

Filtration Coefficient depends on (2)

A

1) properties of glomerular membrane

2) surface area

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28
Q

how does the oncotic pressure of the glomerular capillary bed change from afferent to efferent arterioles?

A

Increase in oncotic pressure.

Water was filtered out, but protein was not (increases protein concentration)

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29
Q

RBF vs RPF

A

RBF = renal BLOOD flow
All blood flow, including hematocrit (volume of blood occupied by cells).
Typical: 1250 mL/min

RPF = renal PLASMA flow
Excludes hematocrit
Typical: 687 mL/min

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30
Q

renal clearance

A

Corresponds to volume of plasma per unit time from which x has been COMPLETELY removed and excreted.

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31
Q

GFR corresponds to the clearance of a compound with the following properties:

A

1) freely filtered (not bound to plasma proteins)
2) not absorbed or secreted
3) Not metabolized or produced by the kidney
4) does not alter GFR

32
Q

Inulin is used to calculate _________.

also: properties, why it is used

A

Inulin is used to calculate GFR.

Small, fructose molecule.
Not absorbed//secreted.
Not made by body (have to inject it)

**Not typically used to calculate GFR. Creatinine clearance is more typical bc don’t need to infuse it

33
Q

PAH is used to calculate ____________.

also: properties

A

Clearance of PAH is used to calculate RENAL PLASMA FLOW.

Freely filtered.
Efficiently secreted (not 100% --> must be corrected for by dividing by 0.9).
Not reabsorbed.
Small organic anion.
Introduced by infusion.
34
Q

how are RBF and GFR regulated?

A

constriction/dilation of afferent/efferent arterioles

35
Q

upstream constriction: impact on RBF/GFR

A

Decrease GFR

Decrease RBF

36
Q

downstream constriction: impact on RBF/GFR

A

Increase GFR

Decrease RBF

37
Q

downstream dilation: impact on RBF/GFR

A

Decrease GFR.

Increase RBF.

38
Q

upstream dilation: impact on RBF/GFR

A

Increase GFR

Increase RBF

39
Q

vasoconstrictor effect on GFR/RPF

A

Ex: norepinephrine
Constricts both afferent/efferent arterioles.
Decreases both GFR and RBF.

Effect: conserve fluid, increase BP

40
Q

vasodilator effect on GFR/RBF

A

Ex: nitric oxide
Dilates both afferent/efferent arterioles.
Increases both GFR and RBF.

Effect: excrete water/salt, reduce BP

41
Q

kidneys filter ____L of fluid per day

A

180 L per day

42
Q

__% of filtered water, Na, Cl, and HCO3 are reabsorbed

A

99% of filtered water, Na, Cl, and HCO3 are reabsorbed

100% of glucose

43
Q

reabsorption in proximal tubule

fraction, osmolarity, driving force

A

2/3 of Na and water are reabsorbed in PCT.

Iso-osmotic: Na is reabsorbed, and water follows so net is same

Driving force: (Na/K)-ATPase in basolateral membrane maintains a low cytoplasmic [Na]

44
Q

transporters present in PCT

A

(Na/K)-ATPase, basolateral: maintains low cytoplasmic [Na+]

Na/H antiporter, apical: uses Na+ gradient to pump H+ out of cell into filtrate.

Na+-coupled transporters, apical: use Na+ gradient to pump glucose/AAs out of filtrate

Passive transporters, basolateral: glucose/AAs move passively back into blood

45
Q

diabetes mellitus

A

Failure to produce/respond to insulin leads to high blood sugar levels.
Na+/glucose cotransporter becomes saturated, so excess glucose appears in the urine.
High urine volume bc water follows solutes (glucose) –> polyuria

46
Q

reabsorption by thin parts loop of henle

percentages, driving force, permeability

A

25% of Na/Cl
23% of water.

Driving force: high osmolarity of interstitial fluid of inner medulla

Descending: IMPERMEABLE to water
Ascending: permeable to water

47
Q

diuretics

A

Prevent uptake of solute –> water is not reabsorbed and stays in filtrate

48
Q

lumenal positive transepithelial potential

A

Drives paracellular uptake of cations.

Between cells, do not have to enter cell.

49
Q

transporters in thick ascending loop of henle

A

(Na/K/2Cl) co-transporter: Na flowing down gradient into cell drives Cl and K to enter too.

Lumenal positive transepithelial potential: drives cations between cells into blood.

50
Q

transporters in distal tubule

A

IMPERMEABLE TO WATER.

Na/Cl cotransporter: Na moving down gradient drives Cl into cell

51
Q

transporters in principal cells (CD)

A

Na+ channels: Na+ flows down gradient into cell.

Aquaporins: water enters cell (exits filtrate, reabsorbed) – controlled by ADH

K+ channel: K+ flows down gradient out of cell into filtrate (secreted) – controlled by aldosterone

52
Q

ADH

A

secreted in response to high PLASMA OSMOLARITY.

Increases water reabsorption

53
Q

diabetes insipidus

A

Fail to make/secrete ADH, or principal cells fail to respond to ADH.
Large volume of urine (up to 18L per day).
Must drink tons of water to compensate.

54
Q

3 types of diuretics

A

furosamide: loop diuretic
thiazide: targets distal tubule
amiloride: inhibits Na channels in collecting duct

55
Q

Na+ excretion responds to ________

A

Na+ excretion responds to VOLUME

56
Q

water excretion responds primarily to __________

A

water excretion responds primarily to plasma osmolality

57
Q

sympathetic nerve activity

stimulated by, effect

A

STIMULATED BY:
volume contraction

EFFECT:
Increased renin
Decreased GFR
Increased Na+ reabsorption in PCT

58
Q

renin/angiotensin

stimulated by, effect

A

STIMULATED BY:
Increased sympathetic nerve activity.
Decreased afferent arteriole pressure.
Decreased GFR.

EFFECT:
Increase BP
Increase Na reabsorption in PCT
Increase secretion of aldosterone/ADH

59
Q

aldosterone

stimulated by, effect

A

STIMULATED BY:
Increased angiotensin II.
Increased [K+] in plasma

EFFECT:
Increased Na reabsorption in CD.
Increased K secretion in CD

60
Q

ADH

stimulated by, effect

A

STIMULATED BY:
Increased plasma osmolarity.
Volume contraction.
Angiotensin II.

EFFECT:
Increased water reabsorption in CD

61
Q

ANP - Atrial Natriuretic Peptide

stimulated by, effect

A

STIMULATED BY:
volume expansion

EFFECT:
Increased GFR.
Decreased renin/aldosterone/ADH.
Decreased Na reabsorption in CD

62
Q

response to volume contraction

A

Increase sympathetic activity (^renin,

63
Q

K+ secretion by principal cells

A

Controlled by aldosterone (secreted in response to high [K+]).

More K+ channels open on apical side, allowing K+ to flow out into filtrate.

Increased activity of Na/K ATPase on basolateral side: more K+ pumped in = more K+ flowing out on apical side)

Increased activity of Na+ channels on apical side: positive in balances the positive out

64
Q

Ca++ reabsorption by late distal tubule and CD

A

Apical Ca channels
Basolateral Ca-ATPase
Basolateral Na/Ca exchanger

*only transcellular uptake in collecting duct are regulated

65
Q

Ca++ uptake by PT and thick ascending loop of henle

A

Apical Ca channels
Basolateral Ca-ATPase
Basolateral Na/Ca exchanger

AND

paracellular uptake of Ca (via luminal positive transepithelial potential)

66
Q

Hypocalcemia

A

Calcitriol secretion = Ca2+ reabsorption in gut and by late distal tubule/CD.

Parathyroid Hormone (PTH) secretion = increased bone resorption and Ca2+ reabsorption by late distal tubule/collecting duct.

67
Q

Hypercalcemia

A

Calcitonin secretion = Bone formation (decreases [Ca2+] plasma).

68
Q

alpha intercalated cells of collecting duct contain…

A
  1. ATP-driven proton pump (V-ATPase) in apical membrane
    - actively pumps protons from the cytoplasm of the cell into the renal fluid
  2. Cl-/HCO3- exchanger in basolateral membrane
    - allows secretion of bicarbonate, preventing cytoplasm from
    becoming too alkaline during acid secretion
69
Q

endogenous anions secreted by proximal tubule

A

prostaglandins

uric acid

70
Q

anionic drugs secreted by proximal tubule

A

penicillin
salicylate
ibuprofin
adefovir (anti-HIV)

71
Q

endogenous cations secreted by proximal tubule

A

epinephrine

norepinephrine

72
Q

cationic drugs secreted by proximal tubule

A

morphine
amiloride
verapamil
vinblastine

73
Q

How are organic anions secreted via the proximal tubule?

A

basolateral:
anion/alpha-ketoglutarate antiporter

apical:
anion/Cl– exchanger

^drives uptake of OA- from circulation.

74
Q

How are organic cations secreted via the proximal tubule?

A

basolateral:
passive transporter brings organic cations in

apical:
1. organic cation/proton antiporter

  1. MDR (ABC ATPase) drives OC+ out actively
75
Q

Competition between different organic anions or cations for the same transporters in the proximal tubule can lead…

A

altered rates of drug clearance and drug toxicity

76
Q

Name an example of a positive benefit of drug competition in the proximal tubule…

A

competition between PAH and penicillin for secretion by proximal tubule –> increased half life of penicillin in circulation

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