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Exam 3 Physiology > Lecture 16 Tubular Reabsorption and Secretion > Flashcards

Lecture 16 Tubular Reabsorption and Secretion Flashcards

1
Q

where must a substance first pass during passive transport?

A

across the tubular epithelial membranes into interstitial fluid

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2
Q

what follows transport across the membranes and renal interstitial fluid?

A

transport through peritubular capillary membrane and back to the blood

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3
Q

what are the two roots water takes from the lumen to the interstitium?

A

transcellular (thru cell) and paracellular(between cells) via osmosis

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4
Q

specific water channels that transport across membrane

A

aquaporins

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5
Q

aquaporin 1 location

A

widespread, including renal tubules

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6
Q

aquaporin 2 locations

A

present in apical membranes of collecting tubule cells

controlled by ADH (secreted from posterior pituitary)

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7
Q

aquaporin 3 locations

A

present in basolateral membranes of collecting tubule cells

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8
Q

what is bulk flow?

A

flow between tubular cells and peritubular capillaries that occur as a result of hydrostatic and osmotic pressures

depends on starling

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9
Q

insertion of more aquaporins in membrane causes…

A

more water reabsorption

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10
Q

ATPase pumps

A

establish ion gradients across the nephron cell membranes

movement of Na

gradients that drive reabsorption or secretion of many other solutes

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11
Q

symport ATPase

A

aka cotransport

moves with Na+ gradient

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12
Q

antiport ATPase

A

solute moves opposite Na+ gradient

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13
Q

Ex. ATPase channels

A

ENaC channel
CFTR
K+ channels
Uniporters

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14
Q

ENaC pump

A

ATPase
found in apical membrane of nephron cells
closed by amiloride (drug)
open by hormones

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15
Q

where are CTFR channels open? what do they transport?

A

chloride

found in apical membranes of some parts of nephron

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16
Q

where are K+ channels located in kidney?

A

found in apical membranes of some parts of nephron

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17
Q

what drives uniporters in cell membranes

A

[gradient] of substance concerned

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18
Q

what type of transport occurs through channels or uniporters

A

facilitated transport

i.e. glucose transport

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19
Q

what type of transport is directly coupled to energy source

A

active transport

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20
Q

what type of transport is coupled indirectly to an energy source (i.e. ion gradient)

A

secondary active transport

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21
Q

primary active transporters ex.

A

Na+K+ ATPase
H+ ATPase
H+K+ ATPase
Calcium ATPase

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22
Q

examples of Secondary active transport in kidney

A

reabsorption of glucose or amino acids by renal tubule

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23
Q

where are sodium glucose cotransporters located?

A

brush border of proximal tubules

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24
Q

SGLT1

A

reabsorbs 10% of glucose in late proximal tubule

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25
Q

SGLT2

A

reabsorbs 90% of glucose in early proximal tubule

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26
Q

what substances are actively secreted into renal tubules?

A

creatine

para-aminohippuric acid

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27
Q

transport maximum

A

rate at which a solute can be transported

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28
Q

what limits transport maximum?

A

saturation of a specific transport system

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29
Q

why would some passively reabsorbed substances not have a transport maximum

A
  • rate of diffusion is deterred by electrochemical gradient of substance
  • permeability of membrane for the substance
  • time fluid containing substance remains in tubule
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30
Q

2 factors rate of transfusion depends on

A

electrochemical gradient

time the substance is in the tubule (tubular flow rate)

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31
Q

solvent drag

A

passive water reabsorption by osmosis is coupled mainly to sedum reabsorption

osmotic movement of water that is carrying some solutes

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32
Q

which of the following (in L/day) represents the GFR in the average adult human?

A. 3
B. 125
C. 180
D. 360

A

180

33
Q

what is the transport max for glucose?

A

375 mg/min

34
Q

which of the following will result in a decrease of glomerular hydrostatic pressure?

a. arterial pressure
b. afferent arterioler resistance
c. efferent arterioler resistance
d. both B and C
E. all of the above

A

B. Afferent arterioler resistance

35
Q

almost 90% of glucose reabsorption occurs in the early proximal tubule. Which of the following mechanism is responsible for moving glucose from the tubular lumen into cytoplasmic compartment?

a. primary active transport via glucose ATPase pump
b. secondary active transport via Na/glucose cotransporter
c. secondary active transport via Na/glucose antiporter
d. diffusion due to concentration differences between tubular fluid and cytoplasm

A

b. secondary active transport via Na/glucose cotransporter

36
Q

proximal tubule composition

A

highly metabolic with large numbers of mitochondria

extensive brush border on luminal surface

extensive intercellular and basal channels on interstitial surfaces

37
Q

what does the proximal tubule reabsorb?

A

65% of filtered Na, Cl, bicarbonate, and K

reabsorb all filtered glucose and amino acids

38
Q

what does proximal tubule secrete?

A

organic acids, bases, and H ions into lumen

39
Q

sodium reabsorption in first half of proximal tubule

A

occurs via co-transport with glucose, amino acid, and other solutes

40
Q

sodium reabsorption in second half of proximal tubule

A

reabsorption is coupled with chloride ions

41
Q

Sodium transport entry is via

A

antiport with H+

42
Q

loop of henle

thin descending loop of hence and permeability

A

highly permeable to water and moderately permeable to most solutes (urea and sodium)

43
Q

how is H + removed from the cell?

A

anti port with Na+

H+ ATPase

44
Q

thin ascending segment of loop of hence and water permeability

A

impermeable to water

45
Q

thick ascending loop of henle transport compositions

A

Na+K+ATPase pump in basolateral membranes

Na,K, Cl co transporter

Slight back leak of K into lumen

46
Q

what is the electrical gradient of the cytoplasm of proximal tubule? tubular lumen?

A

-70mV, -3 mV

47
Q

Luminal Na+ concentration

A

140 mOsm

48
Q

Cytoplasmic Na+ concentration

A

30mOsm

49
Q

describe H+ and bicarbonate ions in proximal tubule

A

H+ increases in lumen due to anti port transport with Na+
H+ combines with luminal bicarbonate to form carbonic acid
carbonic anhydrase in lumen splits carbonic acid into CO2 and Water

50
Q

what happens after Co2 and Water enter the cell?

A

CO2 and water combine to form carbonic acid
carbonic acid dissociates to from bicarbonate ion and H+
bicarbonate ion diffuses out of cel inter intersistial space

51
Q

Na+K+Atpase pump in basolateral membranes of loop of henle…

A

drive reabsorption of K+ into cell against concentration gradient

52
Q

Na, K, Cl co transporter movement

A

1 Na, 2 Cl, and 1 K into cell

53
Q

Leaking of K+ back into lumen causes

A

a positive charge of +8 mv

Mg++ and Ca++ diffusion through tubular lumen through paracellular space into interstitial fluid

54
Q

permeability of the thick ascending segment of loop of henle

A

impermeable to water

site of action of powerful loop diuretics

55
Q

diuretics that act on the loop of henle

A

furosemide
ethacrynic acid
butametanide

56
Q

what does the first portion of the distal tubule form?

A

macula densa

57
Q

function and permeability of distal tubule

A

impermeable to water and urea

reabsorbs most ions (diluting segments)
Na+Cl- cotransporter in luminal membrane
Na+K+ATPase pump in basolateral membrane

58
Q

principle cells of the late distal tubule/corticle collecting tubule

A

reabsorption of Na+ and water from tubular lumen
secretion of K+ into tubular lumen
Use Na+K+ATPase pump
Primary site of K+ sparing diuretics

59
Q

K+ sparing diuretics

A

spironolactone
eplerenon
amiloride
triameterene

60
Q

intercalated cells of the late distal tubule

A

reabsorb K+ from tubular lumen
secrete H+ into tubular lumen (ea. H+ secretion reabsorbs bicarbonate ion, H+ from carbonic anhydrase, mediated by H+ ATPase)

61
Q

intercalated cells (general)

A

reabsorb potassium and bicarbonate ions from lumen and secrete hydrogen ions

62
Q

epithelial cells of medullary collecting duct

A

cuboidal, smooth surfaces with few mitochondria

63
Q

permeability of medullary collecting duct

A

permeable to water (control by ADH)
permeable to urea (use urea transporters_
capable of secreting H+ against lg. [ ] gradient

64
Q

aldosterone

source and site of action

A

from adrenal cortex, acts on principal cells of cortical collecting ducts

65
Q

aldosterone

stimulus for secretion

A

increased levels of extracellular potassium and levels of angiotensin II

66
Q

absence of aldosterone causes

A

addison’s disease, loss of sodium and accumulation potassium

67
Q

function of aldosterone

A

increases sodium reabsorption and stimulates potassium secretion

stimulates Na+/K+ ATPase pump on basolateral side of cortical collecting tubule membrane

68
Q

hyper secretion of aldosterone

A

conn’s syndrome

69
Q

function of Angiotensin II

A

increased sodium and water reabsorption

returns blood pressure and extracellular volume to normal

70
Q

effects of angiotensin II

A

stimulates aldosterone secretion
constricts efferent arterioles
directly stimulates Na reabsorption in proximal tubules, loops of Henle, distal tubules and collecting tubules

71
Q

source of ADH

A

posterior pituitary

72
Q

function of ADH

A

increases water reabsorption

73
Q

effects of ADH

A

binds to V2 receptors in late distal tubules, collecting tubules, and collecting ducts

increases cAMP formation (stimulates movement of Aq-2 proteins to luminal side of cell membranes, form clusters)

74
Q

source and function of Atrial natriuretic Peptide

A

source: cardiac atrial cells in response to distension
function: inhibits reabsorption of sodium and water

75
Q

source and function of Parathyroid hormone

A

source: parathyroid glands
function: increases calcium reabsorption

76
Q

renal clearance of a substance =

A

volume of plasma completely cleared of the substance by the kidneys per unit time

77
Q

mathematical equation for clearance

A

Cs= (US x V)/Ps

Us = urine concentration 
V= urine flow 
Ps= plasma concentration 
Cs= clearance rate
78
Q

GFR and rate of excretion

A

GFR = Us x V

SO GFR= Cs

Exam 3 Physiology (11 decks)

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