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Physiology Exam III Material > Tubular Reabsorption and Secretion > Flashcards

Tubular Reabsorption and Secretion Flashcards

1
Q

Water is transported from the lumen through the tubular cells into the interstitium via both______ and ______ routes by osmosis

A

transcellular, paracellular

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2
Q

Water is transported by way of

A

specific water channels (aquaporins (AQP))

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3
Q

Aquaporin ___ is widespread, including renal tubules

A

1

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4
Q

Aquaporin ____ is present in apical membranes of collecting tubule cells. and is controlled by ADH

A

Aquaporin 2

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5
Q

Aquaporin 2 is present in

A

apical membrane of collecting tubule cells

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6
Q

Aquaporin 2 is controlled by

A

ADH

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7
Q

Aquaporin ___ is present in basolateral membranes of collecting tubule cells

A

3

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8
Q

______ establish ionic gradients across nephron cell membranes

A

ATPases

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9
Q

_____ drive reabsorption or secretion of many other solutes

A

Gradients

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10
Q

What are the two types of secondary active transporters in the nephron

A

Sympoter (cotransport)

Antiport (countertransporter)

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11
Q

after a gradient is established solutes are transported by way of _____ in the nephron cell membranes

A

secondary active transport

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12
Q

ENaC channel is foud

A

in apical membrane of nephron cells

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13
Q

ENaC channel is closed by drug

A

Amiloride

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14
Q

ENaC channel is opened by

A

a number of hormones

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15
Q

CFTR (chloride) channels and K+ channels are found

A

in apical membranes of some segments of a nephron

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16
Q

Are uniporters found on nephron cell membranes

A

yes

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17
Q

Uniporters of the nephron cell membrane are driven by

A

concentration gradient of substance concerned

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18
Q

Transport directly coupled to an energy source is what type of

A

active transport

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19
Q

Transport occurring through channels or uniporters is

A
  • Facilitated transport

- ex. Glucose transport

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20
Q

Transport that is coupled to an energy source (i.e. ion gradient)

A

Secondary active transport

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21
Q

Examples of primary active transport

A
  • Na+K+ ATPase
  • H+ ATPase
  • H+K+ ATPase
  • Calcium ATPase
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22
Q

Reabsorption of glucose or amino acids by renal tubule are examples of

A

secondary active transport

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23
Q

Sodium-glucose co-transporters are located on

A

brush border of proximal tubule cells

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24
Q

What are the two sodium-glucose co-transporters on brush border of proximal tubule cells

A
  • SGLT2

- SGLT1

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25
Q

SGLT2 reabsorbs _____ of glucose in early proximal tubule

A

90%

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26
Q

SGLT1 reabsorbs ___% of glucose in late proximal tubule

A

10%

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27
Q

SGLT2 reabsords 90% of glucose in

A

early proximal tubule

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28
Q

SGLT1 reabsorbs 10% of glucose in

A

late proximal tubule

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29
Q

Substances that are actively secreted into the renal tubules

A

Creatinine

Para-Aminohippuric acid

30
Q

The limit to the rate at which the solute can be transported (transport maximum) is due to

A

saturation of a specific transport system

31
Q

Transport max for glucose

A

375 mg/min

32
Q

Filtered load for glucose

A

125 mg/min

33
Q

GFR x plasma glucose=

A

125 ml/min x 1 mg/ml

34
Q

Reasons that some passively reabsorbed substances do not have a transport maximum

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
35
Q

Rate of transport depends on

A

-The electrochemical gradient

  • Time the substance is in the tubule
    - depends on tubular flow rate
36
Q

Solvent drag

A
  • passive water reabsorption by osmosis is coupled mainly to sodium reabsorption
  • Osmotic movement of water can also carry some solutes=solvent drag
37
Q

What is the GFR (in liters/day) in average adult human

A

125 liters/day

38
Q

Almost 90 percent of glucose reabsorption occurs in the early proximal tubule. by means of

A

secondary active transport via a sodium/ glucose cotransporter

39
Q

The proximal tubule is highly ______ with large numbers of

A

Metabolic, mitochondria

40
Q

Characteristics of the proximal tuble

A
  • highly metabolic with large numbers of mitochondria
  • extensive brush borders on luminal surfaces
  • extensive intercellular and basal channels on interstitial surfaces
41
Q

The proximal tubule reabsorbs

A
  • 65 % of filtered sodium, chloride, bicarbonate and potassium
  • Reabsorbs all filtered glucose and amino acids
42
Q

The proximal convoluted tubule adds what into the lumen tubular fluid

A

H+, organic acids, bases

43
Q

As we go through the proximal convoluted tubule the ratio of tubular fluid/plasma concentration of sodium does what

A

it stays the same (about 1.0)

44
Q

As we go through the proximal tubule the tubular fluid/plasma concentration of creatinine and urea does what

A

increases

45
Q

The proximal tubule secretes what into the tubular lumen

A

organic acids
bases
hydrogen ions

46
Q

in the first half of the proximal tubule sodium reabsorption is via

A

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

47
Q

In the second half of the proximal tubule sodium reabsorption is mainly due to

A

reabsorption with chloride ions

48
Q

Sodium transport in the proximal tubule

A
  • most sodium entry is via antiport with H+
  • Na+ is pumped out of cell via Na+K+ ATPase pump
  • Electrical gradient
    • Cytoplasm= -70mV
    • Tubular lumen= -3 mV
  • Concentration gradient
    • Luminal Na+ concentration=14-mOsm
    • Cytoplasmic Na+ concentration= 30 mOsm
49
Q

What is the proximal tubule luminal Na+ concentration

A

140mOsm

50
Q

What is the proximal tubule cytoplasmic Na+ concentration

A

30 mOsm

51
Q

hyrogen and bicarbonarte ions in the proximal tubule

A
  • H+ increases in lumen due to antiport transport with Na+
  • H+ combines with luminal bicarbonate
  • Forms carbonic acid
  • Carbonic anhydrase in lumen splits carbonic acid into carbon dioxide and water
52
Q

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
53
Q

Carbon dioxide and water in the proximal tubule

A
  • Carbon dioxide and water combine to form carbonic acid
  • Carbon acid dissociates to form bicarbonate ion and H+
  • Bicarbonate ion diffuses out of cell into interstitial space
  • H+ removed form Cell via
    • antiproton with Na+
    • H+ ATPase
54
Q

The thin descending segment of the loop of Henle

A
  • Highly permeable to water and moderately permeable to most solutes, including urea and sodium
  • Reabsorbs about 20% of filtered water
55
Q

The thin ascending segment of the loop of Henle

A

impermeable to water

56
Q

Thick ascending segment in loop of henle

A
  • Na+ K+ ATPase pump in basolateral membranes
    • Drives reabsorption of K+ into cell against concentration gradient
  • Sodium, Potassium, Chloride co-transporter
    • Moves 1-Sodium, 2-Chloride, 1 potassium into cell
  • Slight back lead of K+ into lumen
    • Creates positive charge of +8mv
    • Forces Mg++ and Ca++ to diffuse through tubular lumen through paracellular space into interstitial fluid
  • impermeable to water
  • Site of action of powerful “loop” diuretics
    • Furosemide
    • Ethacrynic acid
    • Bumetanide
57
Q

Powerful diuretics that work on thick ascending segment of the loop of Henle

A
  • Furosemide
  • Ethacrynic acid
  • Bumetanide
58
Q

Source of Aldosterone

A

Adrenal cortex

59
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
60
Q

Aldosterone site of action

A
  • Major site of action is on the principle cells of cortical collecting ducts
61
Q

Stimulus for secretion of Aldosterone

A
  • Increased extracellular potassium

- Increased levels of Angiotensin II

62
Q

Absence of Aldosterone causes

A
  • Addison’s disease

- Results in marked loss of sodium and accumulation of potassium

63
Q

Hypersecretion of Aldosterone is caused from

A

Conn’s syndrome

64
Q

Function of Angiotensin II

A
  • Increased sodium and water reabsorption

- Returns blood pressure and extracellular volume toward normal

65
Q

Effects of Angiotensin II

A
  • Stimulates Aldosterone secretion
  • Constricts efferent arterioles
  • Directly stimulates sodium reabsorption in proximal tubules, loops of Henle, distal tubules, and collecting tubules
66
Q

source of ADH

A

posterior pituitary

67
Q

Function of ADH

A

Increases water reabsorption

68
Q

Effects of ADH

A
  • Binds to V2 receptors in late distal tubules, collecting tubules, and collecting ducts
  • increases formation of cAMP
    • Stimulates movement of aquaporin-2 proteins to luminal side of cell membrane (form cluster)
69
Q

The source of atrial natriuretic peptide

A

-Cardiac atrial cells in response to distension

70
Q

Function of Atrial natriuretic peptide

A

Inhibits reabsorption of sodium and water

71
Q

Source of Parathyroid hormone

A

Parathyroid glands

72
Q

Function of parathyroid hormone

A

Increases calcium reabsorption

Physiology Exam III Material (13 decks)

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