lecture 16 (T3)- Tubular reabsorption and secretion Flashcards Preview

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Flashcards in lecture 16 (T3)- Tubular reabsorption and secretion Deck (67):
1

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

* across the tubular epithelial membranes into the renal interstitial fluid
* through the peritubular capillary membrane back into the blood

2

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

both transcellular and paracellular routes by osmosis

3

what are attributes of aquaporin-1

widespread, including renal tubulesq

4

what are attributes of aquaporin-2

present in apical membranes of collecting tubule cells
controlled by ADH

5

what are attributes of aquaporin-3

present in basolateral membranes of collecting tubule cells

6

what establishes ionic gradients across nephron cell membranes

ATPases

7

what are attributes of ENaC channel

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

8

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

apical membranes

9

what are uniporters in cell membranes driven by

concentration gradient of substance concerned

10

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

facilitated transport
ie: glucose transport

11

what is transport directly coupled to an energy source

active transport

12

what is transport that is coupled indirectly to an energy source

secondary active transport

13

what are examples of primary active transporters

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

14

what does SGLT2 do

reabsorbs 90% of glucose in early proximal tubule

15

what does SGLT1 do

reabsorbs 10% of glucose in late proximal tubule

16

what substances are actively secreted into the renal tubules

creatinine
para-aminohippuric acid

17

what is transport maximum due to

saturation of a specific transport system

18

what is transport maximum

limit to the rate at which the salute can be transported

19

what is the transport max for glucose

375 mg/min

20

what is the filtered load for glucose

125 mg/min

21

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

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

22

what does the rate of transport depend on

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

23

define solvent drag

osmotic movement of water can also carry some solutes
(passive water reabsorption by osmosis is coupled mainly to sodium reabsorption)

24

what are characteristics of the proximal tubule

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

25

what does the proximal tubule reabsorb

all filtered glucose and amino acids
65% of filtered sodium, chloride, bicarbonate and potassium

26

what does the proximal tubule secrete

organic acids, bases and hydrogen ions into tubular lumen

27

what reabsorption occurs in first half of proximal tubule

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

28

what reabsorption occurs in second half of proximal tubule

reabsorption is mainly with chloride ions

29

what is most sodium entry in proximal tubule done by

via anti port with H+

30

what is the electoral gradient of sodium transport in proximal tubule

cytoplasm: -70 mV
tubular lumen: -3 mV

31

what is the concentration gradient for sodium transport in proximal tubule

luminal Na+ concentration= 140mOsm
cytoplasmic Na+ concentration= 30mOsm

32

why does H+ concentration in lumen of proximal tubule increase

due to anti port transport with Na+

33

what does H+ combine with in proximal tubule

luminal bicarbonate, forming carbonic acid

34

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

carbonic anhydrase

35

how is H+ removed from cell in proximal tubule

anti port with Na+
H+ ATPase

36

what are attributes of thin descending segment of loop of henle

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

37

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

NO!!!!

38

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

drives reabsorption of K+ into cell against concentrating gradient

39

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

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

40

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

creates positive charge of +8mv
forces Mg++ and Ca++ to diffuse through tubular lumen through paracellular space into interstitial fluid

41

is the thick ascending loop of hence permeable to water

NOOOOOO

42

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

thick ascending segment of loop of henle

furosemide, ethacrynic acid, bumetanide

43

what forms the macula densa

first portion of distal tubule

44

what is another name for the distal tubule

diluting segment

45

what are principal cells

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

what are examples of aldosterone antagonists

spironolactane and eplerenon

47

what are examples of Na+ channel blockers

amiloride and triamterene

48

what is the main thing that intercalated cells do

reabsorb K+ and bicarbonate from tubular lumen
secrete H+ into tubular lumen

49

what are intercalated cells mediated by

H+ ATPase transporter

50

what are attributes of medullary collecting duct

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

51

what is the source of aldosteron

adrenal cortex

52

what is the function of aldosterone

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

53

what is the site of action for aldosterone

principal cells of cortical collecting ducts

54

what is the stimulus for secretion of aldosterone

increased extracellular potassium
increased levels of angiotensin II

55

what is addisons diesase

absence of aldosterone
results in marked loss of sodium and accumulation of potassium

56

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

Conn's syndrome

57

what is the function of angiotensin II

increased sodium and water reabsorption
returns blood pressure and extracellular volume toward norma;

58

what are the effects of angiotensin II

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

59

what is the source of ADH

posterior pituitary

60

what is the function of ADH

increase water reabsorption

61

what are the effects of ADH

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

what is the source of ANP

cardiac atrial cells in response to distension

63

what is the function of ANP

inhibits reabsorption of sodium and water

64

what is the function of parathyroid hormones

increases calcium reabsorption

65

what is renal clearance of a substance

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

66

what is the equation for renal clearance

Cs X Ps = Us X V

67

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

125 ml of plasma