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

Lecture 16 Tubular Reabsorption and Secretion Flashcards

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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
SGLT2
reabsorbs 90% of glucose in early proximal tubule
26
what substances are actively secreted into renal tubules?
creatine | para-aminohippuric acid
27
transport maximum
rate at which a solute can be transported
28
what limits transport maximum?
saturation of a specific transport system
29
why would some passively reabsorbed substances not have a transport maximum
- rate of diffusion is deterred by electrochemical gradient of substance - permeability of membrane for the substance - time fluid containing substance remains in tubule
30
2 factors rate of transfusion depends on
electrochemical gradient | time the substance is in the tubule (tubular flow rate)
31
solvent drag
passive water reabsorption by osmosis is coupled mainly to sedum reabsorption osmotic movement of water that is carrying some solutes
32
which of the following (in L/day) represents the GFR in the average adult human? A. 3 B. 125 C. 180 D. 360
180
33
what is the transport max for glucose?
375 mg/min
34
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
B. Afferent arterioler resistance
35
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
b. secondary active transport via Na/glucose cotransporter
36
proximal tubule composition
highly metabolic with large numbers of mitochondria extensive brush border on luminal surface extensive intercellular and basal channels on interstitial surfaces
37
what does the proximal tubule reabsorb?
65% of filtered Na, Cl, bicarbonate, and K | reabsorb all filtered glucose and amino acids
38
what does proximal tubule secrete?
organic acids, bases, and H ions into lumen
39
sodium reabsorption in first half of proximal tubule
occurs via co-transport with glucose, amino acid, and other solutes
40
sodium reabsorption in second half of proximal tubule
reabsorption is coupled with chloride ions
41
Sodium transport entry is via
antiport with H+
42
loop of henle thin descending loop of hence and permeability
highly permeable to water and moderately permeable to most solutes (urea and sodium)
43
how is H + removed from the cell?
anti port with Na+ | H+ ATPase
44
thin ascending segment of loop of hence and water permeability
impermeable to water
45
thick ascending loop of henle transport compositions
Na+K+ATPase pump in basolateral membranes Na,K, Cl co transporter Slight back leak of K into lumen
46
what is the electrical gradient of the cytoplasm of proximal tubule? tubular lumen?
-70mV, -3 mV
47
Luminal Na+ concentration
140 mOsm
48
Cytoplasmic Na+ concentration
30mOsm
49
describe H+ and bicarbonate ions in proximal tubule
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
what happens after Co2 and Water enter the cell?
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
Na+K+Atpase pump in basolateral membranes of loop of henle...
drive reabsorption of K+ into cell against concentration gradient
52
Na, K, Cl co transporter movement
1 Na, 2 Cl, and 1 K into cell
53
Leaking of K+ back into lumen causes
a positive charge of +8 mv | Mg++ and Ca++ diffusion through tubular lumen through paracellular space into interstitial fluid
54
permeability of the thick ascending segment of loop of henle
impermeable to water | site of action of powerful loop diuretics
55
diuretics that act on the loop of henle
furosemide ethacrynic acid butametanide
56
what does the first portion of the distal tubule form?
macula densa
57
function and permeability of distal tubule
impermeable to water and urea reabsorbs most ions (diluting segments) Na+Cl- cotransporter in luminal membrane Na+K+ATPase pump in basolateral membrane
58
principle cells of the late distal tubule/corticle collecting tubule
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
K+ sparing diuretics
spironolactone eplerenon amiloride triameterene
60
intercalated cells of the late distal tubule
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
intercalated cells (general)
reabsorb potassium and bicarbonate ions from lumen and secrete hydrogen ions
62
epithelial cells of medullary collecting duct
cuboidal, smooth surfaces with few mitochondria
63
permeability of medullary collecting duct
permeable to water (control by ADH) permeable to urea (use urea transporters_ capable of secreting H+ against lg. [ ] gradient
64
aldosterone | source and site of action
from adrenal cortex, acts on principal cells of cortical collecting ducts
65
aldosterone | stimulus for secretion
increased levels of extracellular potassium and levels of angiotensin II
66
absence of aldosterone causes
addison's disease, loss of sodium and accumulation potassium
67
function of aldosterone
increases sodium reabsorption and stimulates potassium secretion stimulates Na+/K+ ATPase pump on basolateral side of cortical collecting tubule membrane
68
hyper secretion of aldosterone
conn's syndrome
69
function of Angiotensin II
increased sodium and water reabsorption returns blood pressure and extracellular volume to normal
70
effects of angiotensin II
stimulates aldosterone secretion constricts efferent arterioles directly stimulates Na reabsorption in proximal tubules, loops of Henle, distal tubules and collecting tubules
71
source of ADH
posterior pituitary
72
function of ADH
increases water reabsorption
73
effects of ADH
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
source and function of Atrial natriuretic Peptide
source: cardiac atrial cells in response to distension function: inhibits reabsorption of sodium and water
75
source and function of Parathyroid hormone
source: parathyroid glands function: increases calcium reabsorption
76
renal clearance of a substance =
volume of plasma completely cleared of the substance by the kidneys per unit time
77
mathematical equation for clearance
Cs= (US x V)/Ps ``` Us = urine concentration V= urine flow Ps= plasma concentration Cs= clearance rate ```
78
GFR and rate of excretion
GFR = Us x V SO GFR= Cs

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