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Advanced Physiology > Week 11 - Fluid/Electrolyte/Kidney > Flashcards

Week 11 - Fluid/Electrolyte/Kidney Flashcards

1
Q

Volume - Intracellular fluid

A

28.0 L

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2
Q

Volume - Interstitial Fluid

A

11.0L

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3
Q

Volume - Plasma

A

3.0L

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4
Q

Volume - Extracellular Fluid

A

14.0L

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5
Q

Salts are important for:

A

Neuromuscular excitability; secretory activity; membrane permeability; controlling fluid movements

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6
Q

Urine formation results from…

A

glomerular filtration > tubular reabsorption > tubular secretion

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7
Q

Excretion =

A

filtration - reabsorption + secretion

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8
Q

Tubuloglomerular feedback has two mechanisms:

A
  • Afferent feedback mechanism

- Efferent feedback mechanism

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9
Q

Tubuloglomerular feedback: links ? at macula densa with renal arterial resistance and autoregulation of GFR

A

NaCl

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10
Q

Tubuloglomerular feedback: links NaCl at ? with renal arterial resistance and autoregulation of GFR

A

macula densa

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11
Q

Tubuloglomerular feedback: links NaCl at macula densa with ?

A

renal arterial resistance and autoregulation of GFR

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12
Q

GFR = ?

A

Glomerular Filtration Rate

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13
Q

Tubuloglomerular feedback ensures?

A

constant NaCl delivery to distal tubule

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14
Q

Macula densa cells detect decreased NaCl, generates signal with what effects?

A
  1. decreased afferent arteriole resistance to blood flow (increase glomerular hydrostatic pressure - GFR return to normal)
  2. increased renin release from juxtaglomerular cells of afferent and efferent arterioles - activates renin-angiotensin mechanism > causes vasoconstriction of efferent arteriole > increase glomerular hydrostatic pressure - GFR return to normal
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15
Q

Reabsorption - Proximal Tubule - what reabsorbed and %?

A

About 65% of filtered water, Na (slightly lower percentage of Cl) reabsorbed in proximal tubule.

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16
Q

What is the major force of reabsorption of Na, Cl, water at proximal tubule?

A

Na/K ATPase Pump

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17
Q

Mechanisms of Na and Cl transport - proximal tubule

A

First half: Na is reabsorbed by cotransport along with glucose, amino acids, and other solutes.
Second half: Na is reabsorbed mainly with Cl ions.

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18
Q

Secretion - Proximal Tubule

A

Important site for the secretion of waste products of metabolism and harmful drugs/toxins for rapid removal from blood.

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19
Q

Functionally distinct segments of Loop of Henle

A

Thin descending, thin ascending, thick ascending

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20
Q

What happens to water in the descending Loop of Henle?

A

It is highly permeable to water. About 20% of filtered H20 is reabsorbed here.

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21
Q

What happens to water in the ascending Loop of Henle?

A

Both thin and thick segments impermeable to H20.

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22
Q

Compare absorption in thin v. thick ascending Loop of Henle?

A

Thin: much lower reabsorptive capacity, does not reabsorb significant amounts of solute.
Thick: Active reabsorption of Na, Cl, K. About 25% of Na, Cl, K reabsorbed here.

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23
Q

First portion of the ____ forms the macula densa

A

early distal tubule

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24
Q

After macula densa, early distal tubule has similar characteristics to what?

A

thick ascending Loop of Henle

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25
Q

Early Distal Tubule reabsorption

A

Absorbs most ions like Na, Cl, K, and impermeable to water. About 5% of filtered NaCl reabsorbed here.

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26
Q

Late Distal Tubule and Cortical Collecting Duct - composed of 2 distinct cell types:

A

Principle Cells: reabsorb Na+ and H20 and secrete K+ into the lumen.
Type A Intercalated Cells: absorb K and secrete H+

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27
Q

Late Distal Tubule and Cortical Collecting Duct - Functional Characteristics

A
  1. Impermeable to Urea
  2. Reabsorb Na+, rate is under hormonal control (aldosterone)
  3. Secrete K+ (aldosterone)
  4. Can secrete H+ in regulation of acid/base balance
  5. H20 permeability is controlled by concentration of ADH.
28
Q

Reabsorption/Secretion: Medullary Collecting Duct

A

Reabsorb less than 10% of H20, Na but is the final site of urine formation. Extremely important for determining final concentration of urine.

29
Q

Medullary Collecting Duct - Special Characteristics

A
  1. Permeability to H20 is controlled by ADH.
  2. Permeable to urea.
  3. Can secrete H+.
30
Q

What is the final site of urine formation?

A

Medullary Collecting Duct

31
Q

Aldosterone - Role

A

Important regulator of Na reabsorption and K+ and H+ secretion by principle cells.

32
Q

Aldosterone - Mechanism (tubular reabs/secretion)

A

Stimulating Na/K ATPase pump on the basolateral side of the collecting duct membrane and increasing Na permeability on luminal side.

33
Q

Most important stimuli for aldosterone secretion:

A
  1. Increased extracellular [K]

2. Increased Angiotensin II levels

34
Q

Perhaps the body’s most powerful Na-retaining hormone?

A

Angiotensin II

35
Q

What is released as part of the renin-angiotensin mechanism to control bp and osmolarity as well as extracellular fluid?

A

Angiotensin II

36
Q

Angiotensin II is released as part of renin-angiotensin mechanism in order to…

A

control blood pressure, osmolarity and extracellular fluid

37
Q

Angiotensin II increases Na/H2O reabsorption from renal tubules through 3 main effects:

A
  1. Angiotensin II stimulates aldosterone secretion which increases Na reabsorption.
  2. Angiotensin II constricts the efferent arterioles: (> reduces peritubular capillary hydrostatic pressure > increases tubular reabsorption from proximal tubules), (>raises filtration fraction in glomerulus > raises protein concentration in peritubular capillaries > increases reabsorptive force in capillaries and therefore tubular reabsorption)
  3. Directly stimulates reabsorption of Na in renal tubules by stimulating Na/K ATPase Pump, stim. Na/H exchange and Na/HCO3- co-transport.
38
Q

AVP =

A

Arginine Vasopressin

39
Q

What increases water permeability of distal tubule and collecting duct?

A

ADH

40
Q

How does ADH increase H2O permeability?

A

ADH binds to V2 receptors in the late distal tubules and collecting ducts. V2 is a GPCR, so causes formation of cAMP and phosphorylation cascade activation. This stimulates the insertion of AQP-2 into the luminal side of tubular membranes.

41
Q

Insertion of AQP-2 into which side of tubular membranes

A

luminal

42
Q

Maximal urine concentration

A

1200-1400 mOsm/L

43
Q

Minimal urine concentration

A

50-70 mOsm/L

44
Q

Formation of dilute urine: reabsorption character, mechanism

A

Continued electrolyte reabsorption, decreased water reabsorption.
Mechanism: decreased ADH release and reduced water permeability in distal and collecting tubules.

45
Q

Formation of concentrated urine: reabsorption character, mechanism

A

Continued electrolyte reabsorption, increased water reabsorption
Mechanism: Increased ADH release and increased water permeability in distal and collecting tubules
High osmolarity of renal medulla

46
Q

The process by which the medulla interstitial fluid becomes hyper-osmotic involves the ___ mechanism.

A

Countercurrent multiplier mechanism

47
Q

Major factors that contribute to concentration gradient build up in the medulla…

A
  1. Active transport and co-transport of solutes into the interstitium from the thick ascending loop of Henle.
  2. Active transport of solutes from collecting duct into interstitium.
  3. Facilitated diffusion of urea from the collecting ducts into the medullary interstitium ( under ADH control)
  4. Small amount of water reabsorption compared to solute reabs. into the medullary interstitium.
48
Q

Formation of concentrated urine when what levels are high?

A

ADH

49
Q

When ADH levels are high, what type of urine is formed?

A

concentrated

50
Q

A healthy person usually excretes about ___% of the filtered load of urea.

A

20-50%

51
Q

Urea excretion rate generally determined by:

A
  1. conc. of urea in plasma.
  2. GFR.
  3. tubular urea reabsorption
52
Q

In the proximal tubule, ___% of filtered urea is reabsorbed.

A

40-50%

53
Q

40-50% of filtered urea is reabsorbed where:

A

proximal tubule

54
Q

The concentration of urea continues to rise as?

A

the tubular fluid flows in to the thin segments of the Loop of Henle

55
Q

The passive secretion of urea into the loop of Henle is facilitated by:

A

UT-A2

56
Q

UT-A2 facilitates:

A

the passive secretion of urea into the loop of Henle

57
Q

Osmolarity of proximal tubule

A

300mOsm/L

58
Q

Osmolarity - Desc. loop of henle

A

gradually increases until it is nearly equal with that of the ISF (about 1200mOsm/L if blood ADH high)

59
Q

osmolarity - thick ascending loop

A

becomes very dilute…falling to a conc. of about 100mOsm/L

60
Q

Osmolarity - early distal tubule

A

further dilution to about 50mOsm/L

61
Q

Obligatory urine volume

A

The minimum urine volume in which the excreted solute can be dissolved and excreted.
(Solute that needs to be excreted)/(max urine osmolarity) = obligatory urine volume

62
Q

Primary systems that control the amount of sodium and water excreted by the kidneys:

A
  1. The osmoreceptor-ADH mechanism
  2. The thirst mechanism
  3. The renin-angiotensin mechanism
63
Q

Osmoreceptor-ADH regulates:

A

extracellular fluid osmolarity

64
Q

Osmoreceptor-ADH feedback mechanism:

A
  1. An increase in extracellular fluid osmolarity causes osmoreceptors in the anterior hypothalamus to shrink, causing them to fire.
  2. Signal travels to the neurons in the supraoptic nuclei of the hypothalamus causing the release of ADH from secretory granules stored in their axons located in the posterior pituitary.
  3. ADH is released into the bloodstream and increases water permeability in the late distal tubules and collecting ducts.
  4. This causes an increase in water reabsorption and the excretion of low volume, high concentration urine.
  5. This causes a dilution of solutes in the extracellular fluid, correcting osmolarity.
65
Q

Thirst mechanism: what increases thirst?

A
  1. Inc. Plasma osmolarity
  2. Dec. blood volume
  3. Dec. blood pressure
  4. Inc. Angiotensin II
  5. Dry mouth
66
Q

Thirst mechanism: what decreases thirst?

A
  1. Dec. Plasma osmolarity
  2. Inc. blood volume
  3. Inc. blood pressure
  4. Dec. Angiotensin II
  5. Gastric distension

Advanced Physiology (10 decks)

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