Lecture 3-Renal Concentrating Mechanisms And Urine Formation

Question 1

___ is a protein enzyme released by the kidneys when BP is too low

Answer 1

Renin

Question 2

The ___ apparatus is the site of renin synthesis

Answer 2

Juxtaglomerular apparatus

Question 3

The JGA consists of (4) components: 1) modified smooth muscle cells in ___ arteriole; 2) modified smooth muscle cells in the ___ arteriole; 3) extraglomerular ___ cells; 4) ___ cells in the distal tubule

Answer 3

1) modified smooth muscle cells in the afferent arteriole; 2) modified smooth muscle cells in the efferent arteriole; 3) extraglomerular mesangial cells; 4) macula densa cells in the distal tubule

Question 4

Glomerulus blood supply in = ___ arterioles; glomerulus blood supply out = ___ arterioles

Answer 4

In = afferent; out = efferent

Question 5

Renin Angiotensin Pathway—renin causes ___ to be cleaved to ___; ___ converted to ___ in the lung by ___ (inhibited by ___); ___ is the most potent vasoconstrictor known

Answer 5

Renin causes angiotensinogen to be cleaved to angiotensin I; angiotensin I converted to angiotensin II in the lung by angiotensin converting enzyme (inhibited by ACE inhibitors); angiotensin II is the most potent vasoconstrictor known

Question 6

Actions of angiotensin II—vaso___ and ___ (increased/decreased) blood pressure; increased ___ synthesis and release; increased ___ release; increased thirst; feedback inhibition of ___ release

Answer 6

Vasoconstriction and increased blood pressure; increased aldosterone synthesis and release; increased ADH (antidiuretic hormone) release; increased thirst; feedback inhibition of renin release

Question 7

Although angiotensin II constricts both afferent and efferent arterioles, it releases ___, which act to maintain GFR in spite of its constrictive effects

Answer 7

Prostaglandins

Question 8

Angiotensin II acts on the ___ gland to stimulate the release of aldosterone

Answer 8

Adrenal

Question 9

Aldosterone acts on the kidneys to stimulate reabsorption of ___ and ___

Answer 9

Salt and water

Question 10

Aldosterone is a steroid hormone synthesized in the zona ___ of the adrenal cortex

Answer 10

Zona glomerulosa

Question 11

Stimulation for aldosterone release and synthesis include: ___ (increased/decreased) K+ levels in the ECF; angiotensin ___; ___ (increased/decreased) Na+ levels

Answer 11

increased K+ levels in the ECF; angiotensin II; decreased Na+ levels

Question 12

Aldosterone acts on the ___ tubule and collecting ducts to cause K+ and H+ ___ in exchange for ___; net effect is to get rid of ___ and ___

Answer 12

Aldosterone acts on the distal tubule and collecting ducts to cause K+ and H+ secretion (removal) in exchange for Na+; net effect is to get rid of K+ and H+

Question 13

Aldosterone helps to control blood pressure by holding onto ___ and losing ___ from the blood

Answer 13

Holding onto salt and losing potassium

Question 14

___ is a hormone antagonistic to the angiotensin pathway

Answer 14

ANP

Question 15

ANP ___ (increases/decreases) blood volume and pressure by: ___ (increasing/decreasing) the glomerular filtration rate; ___ (increasing/decreasing) reabsorption of Na+ by nephrons; inhibiting the release of ___, ___, and ___

Answer 15

ANP decreases blood volume and pressure by: increasing the glomerular filtration rate; decreasing reabsorption of Na+ by nephrons; inhibiting the release of renin, aldosterone, and ADH

Question 16

Clinical relevance of aldosterone—___ syndrome

Answer 16

Conn’s

Question 17

Conn’s syndrome = ___aldosteronism

Answer 17

Hyper

Question 18

Conn’s syndrome—aldosterone secreting tumor causes ___tension, ___natremia, ___kalemia; eventually, the increased Na+ load exceeds the distal tubule and collecting duct ability to ___ Na+; however, ___ excretion continues and this can be fatal (___kalemia will cause ___polarization of nerve and muscle cells)

Answer 18

Hypertension, hypernatremia, hypokalemia; eventually, the increased Na+ load exceeds the distal tubule and collecting duct ability to reabsorb Na+; however, K+ excretion continues and this can be fatal (hypokalemia will cause hyperpolarization of nerve and muscle cells)

Question 19

Renal concentrating and diluting mechanisms—___ hormone; ___ peptide; the ___ multiplier; the role of ___

Answer 19

Antidiuretic hormone (ADH); atrial natriuretic peptide (ANP); the countercurrent multiplier; the role of urea

Question 20

The kidneys can excrete a large volume of dilute urine or a small volume of concentrated urine without major changes in rates of excretion of solutes such as sodium and potassium—T/F?

Answer 20

True

Question 21

The kidney is able to excrete excess water by forming a ___ (dilute/concentrated) urine

Answer 21

Dilute

Question 22

The kidney conserves water by ___ (diluting/concentrating) the urine

Answer 22

Concentrating

Question 23

Obligatory urine volume is dictated by the maximum ___ ability of the kidney

Answer 23

Maximum concentrating ability of the kidney

Question 24

Obligatory urine volume = ___ L/Day

Answer 24

0.5 L/Day

Example: A normal 70 kg human must excrete 600 mOsm of solute each day; assuming a maximum urine concentrating ability of 1200 mOsm/L. (600 mOsm/Day) / (1200 mOsm/L) = 0.5 L/Day

Question 25

When there is a water deficit in the body, the kidneys form ___ urine by continuing to excrete solutes while ___ (increasing/decreasing) water reabsorption and ___ (increasing/decreasing) the volume of urine formed.

Answer 25

The kidneys form concentrated urine by continuing to excrete solutes while increasing water reabsorption and decreasing the volume of urine formed

Question 26

The human kidney can produce a maximal urine concentration of ___ to ___ mOsm/L, ___ to ___ times the osmolarity of plasma

Answer 26

1200 to 1400 mOsm/L, 4 to 5 times the osmolarity of plasma

Question 27

Antidiuretic hormone (ADH) is also called ___

Answer 27

Arginine vasopressin

Question 28

ADH is synthesized in the ___; it is stored and released from the ___

Answer 28

ADH is synthesized in the hypothalamus; it is stored and released from the posterior pituitary

Question 29

ADH plays a major role in ___ water by ___ urine

Answer 29

Conserving water by concentrating urine

Question 30

Plasma hypotonicity ___ (stimulates/suppresses) ADH release, resulting in excretion of ___ (concentrated/dilute) urine

Answer 30

Suppresses ADH release, resulting in excretion of dilute urine

Question 31

Hypertonicity ___ (stimulates/suppresses) ADH release, which ___ (increases/decreases) the permeability of the collecting duct to water and ___ (increases/decreases) water reabsorption

Answer 31

Hypertonicity stimulates ADH release, which increases the permeability of the collecting duct to water and increases water reabsorption

Question 32

In response to changing plasma sodium levels, changing secretion of ADH can vary urinary osmolality from ___ to ___ mOsm/kg and urinary volume from ___ to ___ L/day

Answer 32

Vary urinary osmolality from 50 to 1200 mOsm/kg and urinary volume from 0.4 to 20 L/day

Question 33

Osmoreceptor-ADH feedback—1) an ___ (increase/decrease) in extracellular fluid osmolarity (which in practical terms means an ___ (increase/decrease) in plasma sodium concentration), causes the special nerve cells called ___ cells, located in the ___ hypothalamus near the ___ nuclei to shrink

Answer 33

An increase in extracellular fluid osmolarity (which in practical terms means an increase in plasma sodium concentration), causes the special nerve cells called osmoreceptor cells, located in the anterior hypothalamus near the supraoptic nuclei to shrink

Question 34

Osmoreceptor-ADH feedback—2) shrinkage of the osmoreceptor cells causes them to fire, sending nerve signals to additional nerve cells in the ___ nuclei, which then relay these signals down the stalk of the pituitary gland to the ___ (anterior/posterior) pituitary

Answer 34

Sending nerve signals to additional nerve cells in the supraoptic nuclei, which then relay these signals down the stalk of the pituitary gland to the posterior pituitary

Question 35

Osmoreceptor-ADH feedback—3) these action potentials conducted to the posterior pituitary stimulate the release of ___, which is stored in secretory granules (or vesicles) in the nerve endings

Answer 35

ADH

Question 36

Osmoreceptor-ADH feedback—4) ADH enters the bloodstream and is transported to the kidneys, where it ___ (increases/decreases) the water permeability of the late ___ tubules, ___ collecting tubules, and ___ collecting ducts

Answer 36

Where it increases the water permeability of the late distal tubules, cortical collecting tubules, and medullary collecting ducts

Question 37

Osmoreceptor-ADH feedback—5) the increased water permeability in the distal nephron segments causes ___ (increased/decreased) water reabsorption and excretion of a ___ (small/large) volume of ___ (dilute/concentrated) urine

Answer 37

Increased water reabsorption and excretion of a small volume of concentrated urine

Question 38

Stimuli for ADH release—___receptors in the hypothalamus respond to effective ECF osmolality—___ (increased/decreased) osmolality stimulates ADH release

Answer 38

Osmoreceptors in the hypothalamus respond to effective ECF osmolality—increased osmolality stimulates ADH release

Question 39

Stimuli for ADH release—___receptors in the atria and aorta will detect ___ (increases/decreases) in volume and stimulate ADH release

Answer 39

Mechanoreceptors in the atria and aorta will detect decreases in volume and stimulate ADH release

Question 40

Other stimuli for ADH release include angiotensin II, fright, nausea, pain, anesthesia, nicotine—T/F?

Answer 40

True

Question 41

Alcohol stimulates ADH release—T/F?

Answer 41

False—alcohol inhibits ADH release

Question 42

Increase ADH—___ (increased/decreased) plasma osmolarity, ___ (increased/decreased) blood volume, ___ (increased/decreased) blood pressure

Answer 42

Increased plasma osmolarity, decreased blood volume, decreased blood pressure

Question 43

Decrease ADH—___ (increased/decreased) plasma osmolarity, ___ (increased/decreased) blood volume, ___ (increased/decreased) blood pressure

Answer 43

Decreased plasma osmolarity, increased blood volume, increased blood pressure

Question 44

How does ADH work? It increases the permeability of the collecting system to ___

Answer 44

Water

Question 45

In the absence of ADH, the collecting system is relatively ___ to water, leading to ___ (increased/decreased) water conservation and a ___ (dilute/concentrated) urine

Answer 45

In the absence of ADH, the collecting system is relatively impermeable to water, leading to decreased water conservation and a dilute urine

Question 46

ADH also increases ___ permeability in the medullary collecting ducts

Answer 46

Urea

Question 47

In order for ADH to work, there must be a driving force to move water out of the tubules and into the interstitium—i.e.: a ___tonic interstitium

Answer 47

A hypertonic interstitium

Question 48

Regardless of whether ADH is present or absent, fluid leaving the early distal tubular segment is ___osmotic, with an osmolarity of only about ___ the osmolarity of plasma

Answer 48

Fluid leaving the early distal tubular segment is hypoosmotic, with an osmolarity of only about 1/3 the osmolarity of plasma

Question 49

The mechanism for forming dilute urine is to continue reabsorbing ___ from the distal segments of the tubular system while failing to reabsorb ___

Answer 49

Continue reabsorbing solutes while failing to reabsorb water

Question 50

In healthy kidneys, fluid leaving the ascending loop of Henle and early distal tubule is always dilute, regardless of the level of ADH—T/F?

Answer 50

True

Question 51

In the absence of ADH, urine is further diluted in the late distal tubule and collecting ducts, and a large volume of dilute urine is excreted, decreasing osmolarity to as low as ___ mOsm/L

Answer 51

50 mOsm/L

Question 52

The basic requirements for forming a concentrated urine are: 1) a ___ (high/low) level of ADH, which increases the permeability of the distal tubules and collecting ducts to water, thereby allowing these tubular segments to avidly reabsorb water; 2) a ___ (high/low) osmolarity of the renal medullary interstitial fluid, which provides the osmotic gradient necessary for water reabsorption to occur in the presence of high levels of ADH; 3) water moves through the tubular membrane by osmosis into the renal ___; from there, it is carried away by the ___ back into the blood

Answer 52

1) a high level of ADH; 2) a high osmolarity of the renal medullary interstitial fluid; 3) water moves through the tubular membrane by osmosis into the renal interstitium; from there, it is carried away by the vasa recta back into the blood

Question 53

The renal medullary interstitium surrounding the collecting ducts is normally ___osmotic (hypo/hyper), so when ADH levels are high, water moves through the tubular membrane by osmosis into the renal ___

Answer 53

Hyperosmotic, renal interstitium

Question 54

The urine-concentrating ability is limited by the level of ___ and by the degree of ___osmolarity of the renal medulla

Answer 54

By the level of ADH and by the degree of hyperosmolarity of the renal medulla

Question 55

Key features of the countercurrent multiplier that help the kidneys to concentrate urine: 1) ___ shape of the loop of Henle allows for flow in ___ directions (this is where the word countercurrent comes from); 2) differences in ___ of certain nephron segments which flow in opposite directions to one another

Answer 55

1) “U” shape of the loop of Henle allows for flow in opposite directions; 2) differences in permeability of certain nephron segments

Question 56

Energy to run the countercurrent multiplier comes from ___

Answer 56

ATP—Na+/K+/ATPase

Question 57

The human kidney can produce a maximal urine concentration of ___ to ___ mOsm/L…___ to ___ times the osmolarity of plasma

Answer 57

1200 to 1400 mOsm/L…4 to 5x the osmolarity of plasma

Question 58

The countercurrent multiplier mechanism depends on the special anatomical arrangement of the ___ and the ___, the specialized peritubular capillaries of the renal medulla

Answer 58

Special anatomical arrangement of the loops of Henle and the vasa recta, the specialized peritubular capillaries of the renal medulla

Question 59

Anatomy of the medullary countercurrent multiplier system—___ nephrons with ___ (long/short) loops of Henle and ___ peritubular capillaries reach into the medulla

Answer 59

Juxtamedullary nephrons with long loops of Henle and vasa recta peritubular capillaries

Question 60

The anatomical relationship of the juxtamedullary nephrons and collecting ducts allows the creation of a ___osmotic gradient in the renal medulla interstitium

Answer 60

Hyperosmotic gradient

Question 61

The osmolarity of the interstitial fluid in the medulla of the kidney is much ___ (lower/higher), and may increase progressively to about ___ to ___ mOsm/L in the pelvic tip of the medulla

Answer 61

Much higher, 1200 to 1400 mOsm/L

Question 62

How does the countercurrent multiplier work?—active transport of ___ and ___ in the ___ loop increases the osmolality of the interstitial space

Answer 62

Active transport of Na and Cl in the thick ascending loop increases the osmolality of the interstitial space

Question 63

Because the thick ascending limb is virtually impermeable to ___, the solutes pumped out (Na and Cl) are not followed by the osmotic flow of ___ into the interstitium

Answer 63

Impermeable to water, are not followed by the osmotic flow of water

Question 64

Fluid that enters the descending limb is still ___-osmotic, but much of it is absorbed in the descending limb, allowing the tubular fluid to become more ___

Answer 64

Iso-osmotic, allowing the tubular fluid to become more concentrated

Question 65

A high concentration of Na Cl in the tubular fluid is delivered to the ___, where solute is pumped to the interstitium, ___ (increasing/decreasing) its osmolality

Answer 65

Thick ascending limb, increasing its osmolality

Question 66

How does solute concentration build up into the renal medulla?—1) active transport of ___ ions and co-transport of ___, ___, and other ions out of the ___ limb of the loop of Henle into the medullary ___; 2) active transport of ions from the ___ ducts into the medullary ___; 3) facilitated diffusion of ___ from the inner medullary collecting ducts into the medullary ___; 4) diffusion of only small amounts of ___ from the medullary tubules into the medullary ___—far less than the reabsorption of ___ into the medullary interstitium

Answer 66

1) active transport of sodium ions and co-transport of potassium, chloride, and other ions out of the thick ascending limb of the loop of Henle into the medullary interstitium; 2) active transport of ions from the collecting ducts into the medullary interstitium; 3) facilitated diffusion of urea from the inner medullary collecting ducts into the medullary interstitium; 4) diffusion of only small amounts of water from the medullary tubules into the medullary interstitium—far less than the reabsorption of solutes into the medullary interstitium

Question 67

The buildup of solute concentration into the renal medulla multiplies the concentration gradient established by the active pumping of ions out of the ___ loop of Henle, eventually raising the interstitial fluid osmolarity to ___ to ___ mOsm/L

Answer 67

Out of the thick ascending loop of Henle, eventually raising the interstitial fluid osmolarity to 1200 to 1400 mOsm/L

Question 68

As solute builds up in the renal medulla, the interstitium becomes very ___osmolar, but unless ___ is present, the tubular fluid stays dilute; when ___ is present, the collecting duct is ___ permeable and the tubular fluid will ___ with the interstitium, creating a concentrated urine

Answer 68

Interstitium becomes very hyperosmolar, but unless ADH is present, the tubular fluid stays dilute; when ADH is present, the collecting duct is water permeable and the tubular fluid will equilibrate with the interstitium, creating a concentrated urine

Question 69

As fluid flows into the cortical collecting tubule, the amount of water reabsorbed is critically dependent on the plasma concentration of ___

Answer 69

ADH

Question 70

In the absence of ADH, this segment [the cortical collecting tubule] is almost impermeable to ___ and fails to reabsorb ___ but continues to reabsorb ___ and further ___ (dilutes/concentrates) the urine

Answer 70

Is almost impermeable to water and fails to reabsorb water but continues to reabsorb solutes and further dilutes the urine

Question 71

When there is a high concentration of ADH, the cortical collecting tubule becomes highly permeable to ___, so large amounts of water are now ___ from the tubule into the cortex interstitium, where it is swept away by the rapidly flowing peritubular capillaries; the fact that these large amounts of water are reabsorbed into the ___, rather than the renal medulla, helps to preserve the ___ (high/low) medullary interstitial fluid osmolarity

Answer 71

Cortical collecting tubule becomes highly permeable to water, so large amounts of water are now reabsorbed from the tubule into the cortex interstitium; the fact that these large amounts of water are reabsorbed into the cortex, rather than the renal medulla, helps to preserve the high medullary interstitial fluid osmolarity

Question 72

The TAL is located in the ___ (inner/outer) medulla, but the osmotic gradient is maximal in the ___ (inner/outer) medulla…how does this work?

Answer 72

TAL is located in the outer medulla, but the osmotic gradient is maximal in the inner medulla…the answer involves urea

Question 73

Urea is a byproduct of ___ metabolism, consisting of 2 ___ molecules

Answer 73

Byproduct of amino acid metabolism, consisting of 2 ammonia molecules

Question 74

Approximately ___-___ g/day of urea are made in the liver

Answer 74

25-30 g/day

Question 75

In cases of liver failure, ammonia levels ___ (increase/decrease) and encephalopathy and coma then develop

Answer 75

Ammonia levels increase

Question 76

Urea contributes to about ___-___% of the osmolarity of the renal medullary interstitium when the kidney is forming a maximally concentrated urine

Answer 76

40-50% of the osmolarity (500 to 600 mOsm/L)

Question 77

Unlike sodium chloride, urea is ___ (actively/passively) reabsorbed from the tubule

Answer 77

Passively

Question 78

When there is a water deficit and blood concentration of ADH is high, ___ (small/large) amounts of urea are passively reabsorbed from the inner medullary collecting ducts into the interstitium

Answer 78

Large amounts

Question 79

The medullary interstitium has a ___ (low/high) concentration of urea; this plays an important role in generating a ___tonic interstitium

Answer 79

High; important role in generating a hypertonic interstitium

Question 80

The TAL is ___ (permeable/impermeable) to water and urea

Answer 80

Impermeable

Question 81

When ___ is present, water is reabsorbed into the cortex and outer medulla; the tubular contents thus become ___ (more/less) concentrated, and a ___ (low/high) concentration of urea reaches the inner medulla

Answer 81

ADH; the tubular contents thus become more concentrated, and a high concentration of urea reaches the inner medulla

Question 82

The inner medulla is permeable to urea only in the presence of ___, and urea diffuses into the interstitium and becomes trapped there

Answer 82

ADH

Question 83

The ___ ascending limb is urea permeable, so some diffuses into the tubule and is recycled

Answer 83

Thin

Question 84

As water flows up the ascending loop of Henle and into the distal and cortical collecting tubules, ___ (small/large) amounts of urea are reabsorbed because these segments are ___ (permeable/impermeable) to urea; in the presence of high concentrations of ADH, water is reabsorbed rapidly from the cortical collecting tubule and the urea concentration ___ (increases/decreases) rapidly because urea ___ (is/is not) very permeable in this part of the tubule

Answer 84

As water flows up the ascending loop of Henle and into the distal and cortical collecting tubules, small amounts of urea are reabsorbed because these segments are impermeable to urea; in the presence of high concentrations of ADH, water is reabsorbed rapidly from the cortical collecting tubule and the urea concentration increases rapidly because urea is not very permeable in this part of the tubule

Question 85

Urea contributes to ___% of the osmolarity of the renal medulla gradient during max urine concentration

Answer 85

40%

Question 86

Urea ___ (actively/passively) diffuses from the medullar collecting duct during water deficits when ___ is present

Answer 86

Passively diffuses during water deficits when ADH is present

Question 87

Urea is recirculated from the medulla interstitium into the loop of Henle and is returned to the tubular fluid—T/F?

Answer 87

True

Question 88

Blood flow is provided to the renal medulla by the ___ to supply the metabolic needs of the cells in this part of the kidney; without a special medullary blood flow system, the solutes pumped into the renal medulla by the countercurrent multiplier system would be rapidly dissipated

Answer 88

Vasa recta

Question 89

2 functions of the vasa recta: 1) remove ___ fluid from the interstitium; 2) ___ (minimize/maximize) solute uptake from the medulla in order to maintain medullary ___tonicity

Answer 89

1) remove reabsorbed fluid from the interstitium; 2) minimize solute uptake from the medulla in order to maintain medullary hypertonicity

Question 90

Countercurrent exchange in the vasa recta—___ blood flow contributes to solute concentration

Answer 90

Medullary blood flow

Question 91

Countercurrent exchange in the vasa recta—medullary blood flow is ___ (high/low); ___-___% of total renal blood flow; sluggish flow minimizes ___ loss

Answer 91

Medullary blood flow is low; 1-2% of total renal blood flow; sluggish flow minimizes solute loss

Question 92

Countercurrent exchange in the vasa recta—___-shaped vasa recta; acts as countercurrent exchangers to minimize ___ loss; little net dilution of interstitium by U-shaped vessels

Answer 92

U-shaped vasa recta; acts as countercurrent exchanges minimize solute loss

Question 93

Blood enters and leaves the medulla by way of the ___ at the boundary of the cortex and renal medulla

Answer 93

By way of the vasa recta

Question 94

The vasa recta, like other capillaries, are highly permeable to ___ in the blood, except for plasma ___

Answer 94

Highly permeable to solutes in the blood, except for plasma proteins

Question 95

In the descending VR, fluid ___ (enters/leaves) the VR; ___ (more/less) fluid ___ than solute ___

Answer 95

In the descending VR, fluid leaves the VR, more fluid leaves than solute enters

Question 96

In the ascending VR, the situation reverses because of the ___ (increasing/decreasing) hydrostatic pressure and ___ (increasing/decreasing) osmolality of the blood

Answer 96

Decreasing hydrostatic pressure and increasing osmolality of the blood

Question 97

Overall, more fluid is ___ than is ___

Answer 97

Reabsorbed than is lost

Question 98

The vasa recta ___ (does/does not) create the medullary hyperosmolarity, but it does prevent it from being ___

Answer 98

Does not create the medullary hyperosmolarity, but it does prevent it from being dissipated

Question 99

Maximum concentrating ability of the kidney is determined not only by the level of ___, but also by the ___ of the renal medulla interstitial fluid

Answer 99

Not only by the level of ADH, but also by the osmolarity of the renal medulla interstitial fluid

Question 100

Even with maximal levels of ADH, urine-concentrating ability will be reduced if medullary blood flow increases enough to reduce the hyperosmolarity in the renal medulla—T/F?

Answer 100

True

Question 101

Disorders of urinary concentrating ability—1) inappropriate secretion of ___—either too much or too little secretion results in abnormal water excretion by the kidneys; 2) impairment of the ___ mechanism; 3) inability of the distal tubule, collecting tubule, and collecting ducts to respond to ___

Answer 101

1) inappropriate secretion of ADH; 2) impairment of the countercurrent mechanism; 3) inability of the distal tubule, collecting tubule, and collecting ducts to respond to ADH

Question 102

Disorders of urinary concentrating ability—2) impairment of the countercurrent mechanism—a ___osmotic medullary interstitium is required for maximal urine concentrating ability; no matter how much ADH is present, maximal urine concentration is limited by the degree of ___osmolarity of the medullary interstitium

Answer 102

A hyperosmotic medullary interstitium; maximal urine concentration is limited by the degree of hyperosmolarity of the medullary interstitium

Question 103

Failure to produce or release ADH from the ___ pituitary = “___” diabetes insipidus

Answer 103

Failure to produce or release ADH from the posterior pituitary = “Central” diabetes insipidus

Question 104

Central DI—the distal tubular segments cannot reabsorb ___ in the absence of ADH; results in the formation of a large volume of ___ urine with urine volumes that can exceed ___ L/day

Answer 104

Cannot reabsorb water in the absence of ADH; results in the formation of a large volume of dilute urine with urine volumes that can exceed 15 L/day

Question 105

Central DI—the primary abnormality observed clinically in people with this condition is the large volume of ___ urine

Answer 105

Dilute

Question 106

Treatment for central DI is administration of a synthetic analog of ADH, ___, which acts selectively on ___ receptors to ___ (increase/decrease) water permeability in the late distal and collecting tubules

Answer 106

Desmopressin, which acts selectively on V2 receptors to increase water permeability in the late distal and collecting tubules

Question 107

“___” diabetes insipidus—___ or ___ levels of ADH are present, but the renal tubular segments ___ (can/cannot) respond appropriately

Answer 107

Nephrogenic diabetes insipidus—normal or elevated levels of ADH are present, but the renal tubular segments cannot respond appropriately

Question 108

Nephrogenic DI—the abnormality resides in the ___

Answer 108

Kidneys

Question 109

Nephrogenic DI can be due to either failure of the ___ mechanism to form a ___osmotic renal medullary interstitium, or failure of the distal and collecting tubules and collecting ducts to respond to ___

Answer 109

Failure of the countercurrent mechanism to form a hyperosmotic renal medullary interstitium, or failure of the distal and collecting tubules and collecting ducts to respond to ADH

Question 110

Nephrogenic DI—many types of renal diseases can impair the concentrating mechanism, especially those that damage the renal ___

Answer 110

Medulla

Question 111

Nephrogenic DI—impairment of the function of the loop of Henle, as occurs with diuretics that inhibit electrolyte reabsorption by this segment, such as ___, can compromise urine-concentrating ability

Answer 111

Furosemide

Question 112

Nephrogenic DI—certain drugs such as ___ and ___ can impair the ability of the distal nephron segments to respond to ADH

Answer 112

Lithium and tetracyclines

Question 113

Diagnosis of nephrogenic DI—can diagnose with test dose of ___

Answer 113

ADH