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Physiology > Renal-Chapter 28 > Flashcards

Renal-Chapter 28 Flashcards

1
Q

Which has a larger value, filtration and reabsorption or urinary excretion?

A

Filtration and reabsorption

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2
Q

Which is more selecitve filtration or reabsorption?

A

Filtration is relatively non-selective

Reabsorption is highly selective

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3
Q

For a substance to be reabsorbed, what are two things it must do?

A

1-Travel across tubular epithelial membrane into renal interstitial fluid

THEN

2-Travel through peritubular capillary membrane into blood

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4
Q

Transcellular route vs paracellular route

A

Transcellular route
Solutes travel through cell membranes of tubular cells into interstitial fluid.
(example=water)

Paracellular route
Solutes travel through spaces between cell junctions of tubular cells into interstitial fluid.

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5
Q

Can Na+ move through transcellular route or paracellular route?

A

BOTH routes

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6
Q

Explain how Na+ moves transceullarly via active transport

A

On basolateral side of of tubular epithelial cell there are extensive Na/K ATPase pumps that pump Na into interstitial fluid and K into tubular epithelial cell. Requires E.

Due to low concentration of Na in tubular epithelial cells, Na is able to passively diffuse into the tubular epithelial (LOW Na) from tubular lumen (HIGH Na).

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7
Q

What is transport maximum

A

The limit to the rate at which a solute can be transported.

When this limit is reached, there can not be any more reabsorbtion and whatever is not reabsorbed will be secreted and excreted in urine.

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8
Q

What does it mean if glucose has reached its threshold during transport?

Example

A

The amount of glucose that has been filtered has reached a point where not all of it will be reabsorbed. The excess glucose will be excreted in urine.

See in diabetes mellitus. There’s so much glucose that it is not reabsorbed in the blood and you will see glucose in urine.

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9
Q

Where does water move as solutes move?

A

Water moves (passively) where ever the solutes go due to osmosis.

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10
Q

As Na+ (and H2O )moves to be reabsorbed into the blood, what does that do to the lumen?

A

Leaves with a (-) charge since Na+ is leaving.

This creates a urea gradient that favors reabsorption. Urea travels passively through urea transporters.

Cl- also increases in lumen and travels paracellularly and passively.

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11
Q

Proximal Tubular reabsorption percentage

  • What’s reabsorbed?
  • What;s secreted?
A

Proximal tubules reabsorb 65 percent of filtered: Na+, Cl-, HCO3-, K+

Reabsorb essentially all filtered glucose and AA

Secretes organic acids, bases, and H+ into tubular lumen.

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12
Q

What are special features of the proximal tubule?

A

Has apical microvilli to increase SA (helps reabsorption)

Also, lots of mitochondria to provide E for active transport.

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13
Q

Generally, why doesn’t osmolarity change in proximal tubule?

A

Because water follows solutes

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14
Q

In proximal tubules, what would it mean if tubular fluid/plasma concentration ratio was less than one? Greater than one?

A

Less than 1
Substance is transported at rates higher than water- everything is reabsorbed
See with glucose and AA

Greater than 1
Transport is slower than water.
See with creatinine.

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15
Q

What type of diffusion is seen in the thin descending segment? Why?

A

Simple diffusion

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16
Q

What is reabsorbed at descending LOH?

A

Highly permeable to water (20 percent of filtered water is reabsorbed here)

Moderately permeable to most solutes (urea, Na+)

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17
Q

Are there are a lot of mitochondria in descending LOH?

A

Few

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18
Q

Is there active reabsorption at descending LOH?

A

Little to no

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19
Q

Ascending thin LOH permeability

A

IMPERMEABLE TO WATER

Permeable to Na+ and urea

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20
Q

Ascending thick LOH permeability

A

IMPERMEABLE TO WATER

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21
Q

Ascending thick LOH reabsorption

A

Reabsorption of about 25 percent of filtered Na+, Cl-, K+ and Ca2+, HCO3-, and Mg2+

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22
Q

Does ascending LOH secrete anything?

A

H+ into tubular lumen

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23
Q

What happens to the tubular fluid in the Thick Ascending LOH?

A

Fluid becomes very dilute and in a hypoosmotic environment

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24
Q

How does Na+, Cl-, and K+ transported into tubular cells in the thick ascending LOH?

  • Ratio
  • Prevents
A

Na+/Cl-/K+ Co-transporter in luminal membrane (Opposite side of Na+/K+ ATPase pump.

Pumps in 1:2:1 ratio respectively.

Prevents reabsorption of Na+ if Na/Cl/K transporter is inhibted

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25
Q

Counter transport active in thick ascending LOH

A

Na+/H+ counter transporter

Na+ transported into tubular cell while H+ transported into tubular lumen

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26
Q

Due to slight positive charge in lumen during filtrate flow in thick ascending LOH, what happens?

A

Positive elements like Na+, K+, Mg2+, and Ca2+ travel paracellularly into the interstitial fluid

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27
Q

Where is the site of action for loop diuretics?

A

Furosemide, ethacrynic acid, bumetanide

Thick ascending LOH…they’ll inhibit Na/Cl/K co-transporter.

This will allow more solutes to stay in the tubular lumen and cause H20 to stay in lumen.

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28
Q 
Of the following, where is there active NaCl transport?
Proximal Tubule
Thin descending LOH
Thin ascending LOH
Thick ascending LOH
A

Proximal tubule

Thick ascending LOH

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29
Q 
Of the following, where is water permeable?
Proximal Tubule
Thin descending LOH
Thin ascending LOH
Thick ascending LOH
A

Proximal tubule

Thin descending LOH

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30
Q 
Of the following, where is NaCl permeable?
Proximal Tubule
Thin descending LOH
Thin ascending LOH
Thick ascending LOH
A

Proximal tubule

Thin descending LOH

Thin ascending LOH

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31
Q 
Of the following, where is ureae permeable?
Proximal Tubule
Thin descending LOH
Thin ascending LOH
Thick ascending LOH
A

Proximal tubule

Thin descending LOH

Thin ascending LOH

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32
Q

What important region is located inbetween the efferent/afferent arterioles and the early distal convoluted tubule?

A

Macula densa

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33
Q

The early distal tubule is similar to what section? How?

A

Similar to thick ascending LOH

Reabsorbs Na+, Cl-, Ca2+, and Mg2+
IMPERMEABLE TO WATER AND UREA

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34
Q

Early distal tubule is also known as the

A

Diluting segment

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35
Q

How are the ascending thick LOH and early distal tubule different. How?

A

How they reasborb Na+

Reabsorbs about 5 percent of filtered Na+

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36
Q

What pumps/means of transportation are observed in the early distal tubule?

A

Na+/K+ ATPase ( transports Na+ into interstitial fluid)

Na+/Cl- co transporter (transports Na+ from lumen into tubular cells).

Cl- can diffuse into interstitial fluid via Cl- channels

37
Q

What can inhibit Na+/Cl- co-transporter in early distal tubule?

A

Thiazide diuretics

38
Q

What are the two types of cells in the late distal tubules and cortical collecting tubules

A

Principal cells

Intercalated cells

39
Q

What do prinicipal cells do?

-controlled by

A

Reabsorb Na+ and secrete K+ into the lumen

aldosterone control

40
Q

What do intercalated cells do?

A

Reabsorb K+ and HCO3- from the lumen and secrete H+ into the lumen.

41
Q

What controls the reabsorption of water in the late distal tubule and cortical collecting tubule?

A

Anti-diuretic hormones (ADH, AVP)

42
Q

What stimulates secretion of aldosterone? What is the effect?

A

Angiotensin II (secretes when low Na+; high ECF K+, and volume depletion)

When aldosterone is released, there is an increase in Na+ and water reabsorption. There’s also an increase in K+ secretion.

  • Stimulates basolateral Na+/K+ ATPase
  • Increases expression of luminal Na+ channels
43
Q

What is aldosterone?

A

Adrenal secreted mineralocorticoid

44
Q

What do K+ sparing diuretics do?

A

Inhibit stimulation of Na+ reabsirption and K+ secretion

Increases water excretion

45
Q

K+ sparing diuretics are an antagonist to

A

Aldosterone

Directly competes with aldosterone for receptors

46
Q

K+ sparing diuretics inhibit what

A

Indirectly inhibits Na+ channel.

Inhibits Na+/K+ ATPase by blocking Na+ reabsorption from lumen

47
Q

What are some K+ sparing diuretics that are aldosterone anatgonists?

A

Spironolactone

Eplerenone

48
Q

What are some K+ sparing diuretics that are Na+ channel blockers?

A

Amiloride

Triamterene

49
Q

What cells are important for acid-base regulation?

A

Intercalated cells (30-40 percent of CT and CD cells)

50
Q

What are the different types of intercalated cells?

A

Type A= eliminates H+ and reabsorbs HCO3- in acidosis

Type B= reabsorbs H+ and secretes HCO3- in alkalosis

51
Q

In late distal tubules and cortical collecting tubules, what controls the permeability of water?

A

ADH

  • high ADH= tubular segments permeable to H2O
  • absence of ADH, impermeable to H2O
  • Diluting and concentrating urine
52
Q

Medullary collecting ducts

  • Reabsorb
  • Secrete
  • Permeability
A

Reabsorbs less than 10 percent of filtered H2O and Na+

Actively reabsorbs Na+

Secretes H+ ions (acid-base balance)

Permeable to urea (urea transporters present)

53
Q

What is the last segment with urine processing ability?

A

Medullary collecting ducts

54
Q

In medullary collecting ducts, what controls the reabsorption of water?

A

ADH

55
Q 
Of the following sections, which has active NaCl transport?
proximal tubule
thin descending LOH
thin ascending LOH
thick ascending LOH
distal tubule
cortical collecting tubule
inner medullary collecting duct
A

All except thin descending LOH and thin ascending LOH

Proximal tubule and thick ascending LOH have more

56
Q 
Of the following sections, which are permeable to H20. Permeable with ADH
proximal tubule
thin descending LOH
thin ascending LOH
thick ascending LOH
distal tubule
cortical collecting tubule
inner medullary collecting duct
A

H20 permeable
Proximal tubule
Thin descending LOH

ADH
Distal tubule
Cortical collecting tubule
Inner medullary collecting duct

57
Q 
Of the following sections, which  are permeable to NaCl
proximal tubule
thin descending LOH
thin ascending LOH
thick ascending LOH
distal tubule
cortical collecting tubule
inner medullary collecting duct
A

Proximal tubule
Thin descending LOH
Thin ascending LOH

58
Q 
Of the following sections, which are permeable to urea?
proximal tubule
thin descending LOH
thin ascending LOH
thick ascending LOH
distal tubule
cortical collecting tubule
inner medullary collecting duct
A

Proximal tubule
Thin descending LOH
Thin ascending LOH

With ADH
Inner medullary collecting duct

59
Q

As glomerular filtrate passes through tubule, what percent of water gets reabsorbed?

A

99 (and most solutes)

60
Q

What forces determine rate of reabsorption in peritubular caps?

A

Hydrostatic and colloid osmotic pressure

61
Q

For peritubular capillaries

If you increase arterial pressure what will happen to hydrostatic pressure and reabsorption?

A

Increase peritubular hydrostatic pressure

Decrease reabsorption

62
Q

If you increase resistance of afferent and efferent arterioles, what happens to peritubular capillary and reabsorption?

A

Capillary pressure will decrease

Reabsorption will increase

63
Q

What are the 2 major forces that regulate capillary hydrostatic pressure?

A

Arterial pressure

Resistance of afferent and efferent arterioles

64
Q

What effects does systemic colloid osmotic pressure have on peritubular capillaries?

A

Increase in plasma protein concentration will increase colloid osmotic pressure in peritubular capillaries and increase reabsorption

65
Q

If filtration fraction is increased with the peritubular capillaries, what happens to reabsorption?

A

Reabsorption in the peritubular capillaries will increase when there’s an increase in filtration fraction.

66
Q

T/F Generally, forces that increase peritubular capillary reabsorption also decreases renal tube reabsorption

A

F

Increase in peritubular capillary reabsorption has increase in renal tubule reabsorption

67
Q

Hemodynamic changes that decrease peritubular capillary reabsorption will do what to tubular reabsorption?

A

Decrease

68
Q

The colloid osmotic pressure of peritubular capillaries are determined by

A

Systemic plasma colloid osmotic pressure

Filtration fraction

69
Q

Aldosterone

  • Site of action
  • Effects
A

Collecting tubule and duct

Increase NaCl
Increase H2O reabsorption
Increase K+ secretion

70
Q

Angiotensin II

  • Site of action
  • Effects
A

Proximal tubule, thick ascending LOH, distale tubule, collecting tubule

Increase NaCl
Increase H2O reabsorption
Increase H+ secretion

71
Q

ADH

  • Site of action
  • Effects
A

Distal tubule, collecting tubule and duct

Increase H2O reabsorption

72
Q

Atrial natriuretic peptide

  • Site of action
  • Effects
A

Distal tubule, collecting tubule and duct

Decrease NaCl reabsorption

73
Q

Parathyroid hormone

  • Site of action
  • Effects
A

Proximal tubule, thick ascending LOH, distal tubule

Decrease PO4 reabsorption
Increase Ca2+ reabsorption

74
Q

T/F Aldosterone increases Na+ reabsorption and stimulates K+ reabsorption

A

F

Increases Na+ reabsorption
K+ secretion

75
Q

What are zona glomerulose cells

A

In the adrenal cortex

Secrete aldosterone

76
Q

Principal cells of late distal tubules and cortical collecting ducts when aldosterone present does 3 things

A

-Stimulates Na+/K+ ATPase on basolateral membrane

Increases Na+ permeability on luminal membrane

Increases K+ secretion into tubular fluid

77
Q

What are stimuli for secretion when aldosterone is present?

A

Increased extracellular K+ concentration

Angiotensin II

78
Q

What is Conn’s Syndrome

A

Excessive amount of aldosterone secretion

  • Na+ retention
  • Decreased plasma K+ concentration due to xs K+ secretion
79
Q

What is Addison’s disease

A

No aldosterone secretion

  • Loss of Na+ from body
  • Accumulation of K+ in ECF
80
Q

What is the body’s most powerful salt-retaining hormone?

A

Angiotensin II

81
Q

Renin release is stimulated by (2)

-Give examples

A

Low blood pressure or low ECF volume

Hemorrhage
Severe diarrhea

82
Q

What is the mechansm to increase salt and water reabsorption with angiotensin II

A

Aldosterone is released

Constriction of efferent arterioles

  • Decreases hydrostatic pressure of peritubular capillaries
  • Increase colloid osmotic pressure in peritubular capillaries

Stimulate Na+ reabsorption

83
Q

Angiotensin II stimulates Na+ reabsorption where?

A

Proximal tubule

LOH

Distal tubule

Collecting tubule

84
Q

Angiotensin II stimulates what in the luminal membrane and tubular cell?

A

Na+/H+ exchange

Stimulates Na+/K+ ATPase

Stimulates Na+/HCO3- cotransport on basolateral membrane

85
Q

ADH or Arginine vasopressin increases water permeability where

A

DT

CT

CD

86
Q

How does ADH work?

A

Binds to V2 receptors

Stimulates production of cAMP

Apical membrane insertion of water channels

Water travels down concentration gradient and is rapidly reabsorbed

87
Q

How does Atrial natriuretic peptide work?

A

Increased plasma volumed causes atria to release ANP

Water and Na+ reabsorption in inhibited in the CD

Increased urine excretion and decreased blood volume

(Dangerous when congestive heart failure when atria are stretched)

88
Q

How does parathyroid horome

A

Low extracellular concentration of free Ca2+ causes realease of parathyroid hormone from parathyroid gland

Increase Ca2+ reabsorption in thick ascending LOH and DT

Inhibits PO4 reabsorption
Stimulates Mg2_ reabsorption

89
Q

How can sympathetic nervous system increase Na+ reabsorption

A

Strong sympathetic nervous system can constrict the afferent and efferent arteriole to reduce GFR.

Low levels of sympathetic activity will increase Na+ reabsorption in the PT and LOH (noepinephrine->alpha adrenergic receptor)

Sympathetic nervous system activation increases renin release and angiotensin II formation

Physiology (18 decks)

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