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physiology (Woods) > lecture 16 (T3)- Tubular reabsorption and secretion > Flashcards

lecture 16 (T3)- Tubular reabsorption and secretion Flashcards

1
Q

what must happen for a substance to be reabsorbed (it must first be transported):

A
  • across the tubular epithelial membranes into the renal interstitial fluid
  • through the peritubular capillary membrane back into the blood
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2
Q

what is wanter transported form the lumen through the tubular cells into the interstitial by

A

both transcellular and paracellular routes by osmosis

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3
Q

what are attributes of aquaporin-1

A

widespread, including renal tubulesq

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4
Q

what are attributes of aquaporin-2

A

present in apical membranes of collecting tubule cells

controlled by ADH

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5
Q

what are attributes of aquaporin-3

A

present in basolateral membranes of collecting tubule cells

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6
Q

what establishes ionic gradients across nephron cell membranes

A

ATPases

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7
Q

what are attributes of ENaC channel

A

found in apical membrane of nephron cells
closed by drug amiloride
opened by a number of hormones

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8
Q

where are CFTR (chloride channels) and K+ channels sometimes found on some segments of nephrons

A

apical membranes

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9
Q

what are uniporters in cell membranes driven by

A

concentration gradient of substance concerned

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10
Q

what is an transport occurring through channels or uniporters and an example

A

facilitated transport

ie: glucose transport

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11
Q

what is transport directly coupled to an energy source

A

active transport

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12
Q

what is transport that is coupled indirectly to an energy source

A

secondary active transport

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13
Q

what are examples of primary active transporters

A

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

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14
Q

what does SGLT2 do

A

reabsorbs 90% of glucose in early proximal tubule

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15
Q

what does SGLT1 do

A

reabsorbs 10% of glucose in late proximal tubule

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16
Q

what substances are actively secreted into the renal tubules

A

creatinine

para-aminohippuric acid

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17
Q

what is transport maximum due to

A

saturation of a specific transport system

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18
Q

what is transport maximum

A

limit to the rate at which the salute can be transported

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19
Q

what is the transport max for glucose

A

375 mg/min

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20
Q

what is the filtered load for glucose

A

125 mg/min

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21
Q

what are some reasons that some passively reabsorbed substances do not have a transport max

A

rate of diffusion is determined by electrochemical gradient of the substance
permeability of the membrane for the substance
time that the fluid containing the substance remains within the tubule

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22
Q

what does the rate of transport depend on

A

the electrochemical gradient

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

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23
Q

define solvent drag

A

osmotic movement of water can also carry some solutes

passive water reabsorption by osmosis is coupled mainly to sodium reabsorption

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24
Q

what are characteristics of the proximal tubule

A 
highly metabolic (large number mitochondria)
extensive brush border on luminal surfaces
extensive intercellular and basal channels on interstitial surfaces
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25
Q

what does the proximal tubule reabsorb

A

all filtered glucose and amino acids

65% of filtered sodium, chloride, bicarbonate and potassium

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26
Q

what does the proximal tubule secrete

A

organic acids, bases and hydrogen ions into tubular lumen

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27
Q

what reabsorption occurs in first half of proximal tubule

A

reabsorption is via co-transport along with glucose, amino acids, and other solutes

28
Q

what reabsorption occurs in second half of proximal tubule

A

reabsorption is mainly with chloride ions

29
Q

what is most sodium entry in proximal tubule done by

A

via anti port with H+

30
Q

what is the electoral gradient of sodium transport in proximal tubule

A

cytoplasm: -70 mV

tubular lumen: -3 mV

31
Q

what is the concentration gradient for sodium transport in proximal tubule

A

luminal Na+ concentration= 140mOsm

cytoplasmic Na+ concentration= 30mOsm

32
Q

why does H+ concentration in lumen of proximal tubule increase

A

due to anti port transport with Na+

33
Q

what does H+ combine with in proximal tubule

A

luminal bicarbonate, forming carbonic acid

34
Q

what splits carbonic acid into CO2 and water in the proximal tubule

A

carbonic anhydrase

35
Q

how is H+ removed from cell in proximal tubule

A

anti port with Na+

H+ ATPase

36
Q

what are attributes of thin descending segment of loop of henle

A

highly permeable to water and moderately permeable to most solutes (including urea and sodium)
reabsorbs about 20% of filtered water

37
Q

is the thin ascending segment of the loop of henle permeable to water

A

NO!!!!

38
Q

what does the Na+K+ ATPase pump in the basolateral membranes of the thick ascending segment do

A

drives reabsorption of K+ into cell against concentrating gradient

39
Q

what does the sodium. potassium, chloride co-transporter do in the thick ascending segment

A

moves 1 sodium, 2 chloride and 1 potassium into the cell

40
Q

what does the slight back leak of K+ into the lumen in the thick ascending segment of the loop of hence do

A

creates positive charge of +8mv

forces Mg++ and Ca++ to diffuse through tubular lumen through paracellular space into interstitial fluid

41
Q

is the thick ascending loop of hence permeable to water

A

NOOOOOO

42
Q

what is the site of action of powerful loop diuretics and what are they

A

thick ascending segment of loop of henle

furosemide, ethacrynic acid, bumetanide

43
Q

what forms the macula densa

A

first portion of distal tubule

44
Q

what is another name for the distal tubule

A

diluting segment

45
Q

what are principal cells

A

reabsorb Na+ and water from tubular lumen
secrete K+ into tubular lumen
uses Na+K+ ATPase pump
primary site of K+ sparing diuretics (spironoactone, eplerenone, amiloride, triameterene)

46
Q

what are examples of aldosterone antagonists

A

spironolactane and eplerenon

47
Q

what are examples of Na+ channel blockers

A

amiloride and triamterene

48
Q

what is the main thing that intercalated cells do

A

reabsorb K+ and bicarbonate from tubular lumen

secrete H+ into tubular lumen

49
Q

what are intercalated cells mediated by

A

H+ ATPase transporter

50
Q

what are attributes of medullary collecting duct

A

epithelial cells are cuboidal
permeability to water controlled by ADP
permeable to urea
capable of secreting H+ against a large concentration gradient

51
Q

what is the source of aldosteron

A

adrenal cortex

52
Q

what is the function of aldosterone

A

increases sodium reabsorption and stimulates potassium secretion
stimulates Na+K+ ATPase pump on basolateral side of cortical collecting tubule membrane

53
Q

what is the site of action for aldosterone

A

principal cells of cortical collecting ducts

54
Q

what is the stimulus for secretion of aldosterone

A

increased extracellular potassium

increased levels of angiotensin II

55
Q

what is addisons diesase

A

absence of aldosterone

results in marked loss of sodium and accumulation of potassium

56
Q

what is the diseased caused when there is hyper secretion of aldosterone

A

Conn’s syndrome

57
Q

what is the function of angiotensin II

A

increased sodium and water reabsorption

returns blood pressure and extracellular volume toward norma;

58
Q

what are the effects of angiotensin II

A

stimulates aldosterone secretion
constricts efferent arterioles
directly stimulates sodium reabsorption in proximal tubules, loop of henle, distal tubules, and collecting tubules

59
Q

what is the source of ADH

A

posterior pituitary

60
Q

what is the function of ADH

A

increase water reabsorption

61
Q

what are the effects of ADH

A

binds to V2 receptors in late distal tubules collecting tubules, and collecting ducts
increases formation of cAMp( stimulating movement of aquaporin 2 proteins to lumen side of cell membranes)

62
Q

what is the source of ANP

A

cardiac atrial cells in response to distension

63
Q

what is the function of ANP

A

inhibits reabsorption of sodium and water

64
Q

what is the function of parathyroid hormones

A

increases calcium reabsorption

65
Q

what is renal clearance of a substance

A

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

66
Q

what is the equation for renal clearance

A

Cs X Ps = Us X V

67
Q

how much plasma flowing through the kidneys must be filtered to deliver the inulin that appears in the urin

A

125 ml of plasma

physiology (Woods) (18 decks)

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