Physiology - Pulmonary / Renal Block (II)

Question 1

A 20-year-old, unresponsive woman is brought to the ED with respiratory distress after ingesting ‘ecstasy’ and subsequently drinking large amounts of fluid.

Her lab results are shown below. Explain why she has these results.

Electrolytes:

• Na⁺ — 117 mmol/L*
• Cl^- — 87 mmol/L*
• HCO₃^- — 15 mmol/L*

Serum osmolarity: 245 mOsm/kg

Urine specific gravity: 1.015

Answer 1

Her large intake of fluid has (due to dehydration and extreme thirst caused by ecstasy) has diluted out her electrolytes, so all are low, and her fluids are extremely dilute

Question 2

In a healthy adult, what percentage of the body is typically made up by adipose?

What is the rest classified as?

Answer 2

20% (men: 10 - 20; women: 18 - 25);

lean body mass (80%)

Question 3

How many liters of water are found in the average healthy 70 kg individual?

How much of this is intracellular? Extracellular? Plasma?

Answer 3

40 L;

25 L

15 L (11.5 L interstitial; 3.5 L plasma)

Question 4

What is the 60-40-20 rule of thumb for fluids?

Answer 4

60% of body weight

40% intracellular

20% extracellular

Question 5

What is the state of the water in the interstitium?

Answer 5

It is gel-like (combined with ground substance and other extracellular materials)

Question 6

What term describes excess fluid in the interstitial space?

Answer 6

Edema

Question 7

What proportion of lean body mass is water?

What percentage of a healthy individual is made up by lean body mass (non-adipose tissues, including water)?

Answer 7

73%;

80%

Question 8

Body fat = Total weight - ____________________.

Lean body mass = total body water / _____.

Answer 8

Lean body mass;

0.73

Question 9

Calculate the lean body mass and adipose fraction for the following patient.

5’4 woman

91 kg weight

40 L water

Answer 9

40 L / 0.73 = 54.8 L lean body mass

91 - 54.8 = 36.2 kg fat

36.2/91 = 40% adipose

Question 10

Obesity can be defined by an individual’s adipose content (as a fraction of weight).

What percentage defines obesity in a man?

What percentage defines obesity in a woman?

Answer 10

≥ 25%

≥ 32%

Question 11

What proportion of body water is intracellular?

What proportion is extracellular?

Of the extracellular, what proportion is plasma?

Answer 11

~2/3

~1/3

~1/4

Question 12

The quantity of a substance in fluid is equal to the volume of fluid multiplied by:

Answer 12

The concentration of the substance

(Quantity = volume * concentration)

Question 13

Evans blue dye is a substance that binds plasma proteins.

You administer 10 mg into an 80 kg patient’s bloodstream and remove a sample 10 min later. The evans blue dye concentration of the sample is 0.4 mg / 100 mL.

What is the plasma volume of the individual?

What is the blood volume of the individual?

Answer 13

Quantity administered = volume * concentration

10 mg = V * 0.4 mg / 100 mL

10 mg / 0.4 mg / 100 mL = V = 2500 mL

Plasma volume / fraction of plasma in the blood = blood volume

2500 mL / 0.55 = 4546 mL

Question 14

What body fluid compartment volumes can be directly measured?

Which can only be indirectly measured?

Answer 14

Total body water,

ECF, plasma, blood volume;

ICF,

interstitial fluid

Question 15

What substance can be used to measure total body water?

What substance can be used to measure ECF?

What substance can be used to measure blood volume?

What substance can be used to measure plasma volume?

Answer 15

D₂O

Inulin

Radiolabeled iron

Radiolabeled albumin

Question 16

How is the anion gap measured?

Answer 16

Cations - anions

(Na⁺ + K⁺) - (Cl^- + HCO₃^-)

Question 17

Calculate the anion gap for the following electrolytes.

Na⁺ — 117 mmol/L

Cl^- — 87 mmol/L

HCO₃^- — 15 mmol/L

K⁺ — 4 mmol/L

Answer 17

(117 + 4) - (87 + 15) = 19

Question 18

Besides electrolyte abnormalities, what might cause a change in the anion gap?

Answer 18

A change in organic anion concentrations (e.g. protein, ketones, etc.)

Question 19

A 20-year-old, unresponsive woman is brought to the ED with respiratory distress after ingesting ‘ecstasy’ and subsequently drinking large amounts of fluid.

Her lab results are shown below. What is your diagnosis?

Electrolytes:

• Na⁺ — 117 mmol/L*
• Cl^- — 87 mmol/L*
• HCO₃^- — 15 mmol/L*

Serum osmolarity: 245 mOsm/kg

Urine specific gravity: 1.015

Answer 19

Hyponatremia;

cerebral and pulmonary edema

(hypoosmolar syndrome)

Question 20

What is the normal serum osmolality?

True/False. It is not a colligative property.

Answer 20

290 mOsm/kg;

false

Question 21

What is a severe consequence of body hypoosmolality?

Answer 21

Cerebral edema (and eventual death)

Question 22

Describe how each of the following will impact the ECF:

1. An infusion of hypotonic fluid
2. An infusion of isotonic fluid
3. An infusion of hypertonic fluid

Answer 22

1. Expands by less than the volume infused
2. Expands by the volume infused
3. Expands by more than the volume infused

Question 23

How is the renal fraction calculated?

What is it normally?

Answer 23

Renal blood flow / cardiac output

20%

Question 24

True/False.

The kidneys use up virtually 100% of the oxygen they receive.

Answer 24

False.

The kidneys actually use very little of the oxygen coming in and there is some shunting of oxygen through the arteriovenous system

Question 25

**True/False**. The renal arterial system is non-anastomotic, and it is easy for small segments to be infarcted.

Answer 25

True.

Question 26

**True/False**. Albumin's size is the main reason it doesn't leave the glomerulus through the filtration slits.

Answer 26

**False**. Its _charge_ is the main reason it doesn't pass through

Question 27

Protein loss in the urine will happen either because of loss of the _____________ or a widening of the \_\_\_\_\_\_\_\_\_\_\_\_.

Answer 27

Charge barrier; filtration slits

Question 28

Renal resistance happens in which vessels?

Answer 28

The arteries, afferent arteriole, and efferent arteriole

Question 29

The glomerular filtration rate is maintained at a high pressure to overcome what pressure that would keep fluid in the glomerulus?

Answer 29

The colloid osmotic pressure (hydrostatic pressure - osmotic pressure)

Question 30

What is the average GFR? What is the average renal blood flow?

Answer 30

125 mL / min *(180 L / day)*; 1200 mL / min

Question 31

What are the three intrinsic mechanisms of renal blood flow control?

Answer 31

Autoregulation *(myogenic)* Tubuloglomerular feedback *(tubular pressures increase --\> glomerular pressure increases in response)* Paracrine factors

Question 32

What are the main extrinsic mechanisms of renal blood flow control?

Answer 32

Sympathetic nerves Hormones (including ANP)

Question 33

Which are the vasoconstricting hormones affecting renal blood flow?

Answer 33

Epinephrine Angiotensin II Endothelin

Question 34

Which are the vasodilating hormones affecting renal blood flow?

Answer 34

Prostaglandins Bradykinin Atrial natriuretic peptide Nitric oxide

Question 35

Does angiotensin II affect glomerular filtration or systemic arteriolar constriction?

Answer 35

Both

Question 36

In what electrolyte circumstance is an NSAID more likely to decrease GFR?

Answer 36

Sodium-depleted circumstances | (increased vasoconstriction effect)

Question 37

Atrial natriuretic peptide causes a decrease in the release of what two other hormones? What effect does ANP have on the vasculature?

Answer 37

Renin, aldosterone; renal vasodilation

Question 38

What effect do tubuloglomerular feedback and autoregulation have on renal blood flow? What effect do they have on GFR?

Answer 38

Both maintained during fluctuations in arterial pressure

Question 39

What effect does the renin-angiotensin system have on renal blood flow? What effect do they have on GFR?

Answer 39

Reduces both

Question 40

What substance partially counteracts the effects of angiotensin II?

Answer 40

Prostaglandins

Question 41

Via what clearance equation is GFR calculated?

Answer 41

Clearance_x = Urine flow \* Urine_x / Plasma_x

Question 42

**True/False**. In order for a substance to be useful in calculating GFR via the clearance equation, it must be: freely filtered at the glomerulus, not reabsorbed or secreted, not metabolized or degraded, easily measured.

Answer 42

**True**.

Question 43

What are some endogenous substances that can be used for measuring GFR?

Answer 43

Inulin; mannitol; radiolabeled compounds

Question 44

Calculate the GFR for the following patient using the results of this 24-hour urine collection: 1.6 L urine Urine creatinine 105 mg / dL Plasma creatinine 0.9 mg / dL

Answer 44

**130 ml/min** ((1600 mL / 24 hours / 60 min) \* 105 mg / dL) / 0.9 mg / dL

Question 45

The plasma concentration of what substance is a good indicator of their GFR? What is a normal value for this substance?

Answer 45

Creatinine; 1 mg/dL

Question 46

If the plasma creatinine level is 1, what does this indicate about the glomerular filtration rate? If it increases to 2, what does this indicate? If it increases to 3, what does this indicate? If it increases to 4, what does this indicate?

Answer 46

**Normal** GFR *(~120 mL/min) (i.e. 100%/1)* GFR down to **50**% *(~60 mL/min) (i.e. 100%/2)* GFR down to **33**% *(~40 mL/min) (i.e. 100%/3)* GFR down to **25**% *(~30 mL/min) (i.e. 100%/4)*

Question 47

What would a plasma creatinine concentration of 5 roughly indicate about GFR?

Answer 47

A GFR of 24 mL/min (normal: 120 mL/min) (100% function / 5)

Question 48

Calculate the GFR for the following patient using the results of this 24-hour urine collection: Urine flow: 3 mL/min Urine inulin 9.5 mg / mL Plasma inulin 0.26 mg / mL

Answer 48

**110 mL/min** (UF \* U_x)/P_x

Question 49

If calculating GFR via renal plasma flow, what equation would be used?

Answer 49

Renal plasma flow = (Urine flow \* Urine_x) / (P_a(x) - P_v(x))

Question 50

What is a useful substance for calculating GFR via renal plasma flow? Why?

Answer 50

Para-aminohippurate; it is fully secreted

Question 51

**True/False**. Measuring GFR via clearance necessitates a substance that is fully filtered. AND Measuring GFR via renal plasma flow necessitates a substance that is neither secreted nor reabsorbed.

Answer 51

**False**. ## Footnote * Measuring GFR via _renal plasma flow_ necessitates a substance that is fully filtered (e.g. para-aminohippurate).* * AND* * Measuring GFR via _clearance_ necessitates a substance that is neither secreted nor reabsorbed (e.g. inulin).*

Question 52

If a substance's clearance is less than the GFR, what does this indicate?

Answer 52

There is net reabsorption

Question 53

If a substance's clearance is greater than the GFR, what does this indicate?

Answer 53

There is net secretion of the substance

Question 54

If a substance's clearance is less than the GFR, what does this indicate? If a substance's clearance is greater than the GFR, what does this indicate?

Answer 54

Net reabsorption; net secretion

Question 55

Where does the majority (67%) of filtered sodium and water get reabsorbed in the nephron? Where does the next 25% get reabsorbed? And the final 7 - 8%?

Answer 55

The proximal convoluted tubule; the loop of Henle; the DCT/collecting duct

Question 56

**True/False**. \< 1% of filtered water and sodium actually gets excreted in the urine.

Answer 56

**True**.

Question 57

Describe the relative amounts of sodium and water reabsorbed in each part of the nephron.

Answer 57

Question 58

Which portion of the nephron is known as the 'bulk reasborber?'

Answer 58

The proximal convoluted tubule

Question 59

Basolateral Na⁺/K⁺ ATPases maintain a low sodium concentration in the proximal tubular cells. What process does this facilitate and of what substances?

Answer 59

Apical reabsorption via sodium-linked cotransport; glucose, amino acids, lactate, citrate, succinate, etc.

Question 60

Via what mechanism is sodium maintained at a very low concentration in proximal tubule cells so that a gradient exists for sodium-linked cotransport of a variety of organic anions and other substances?

Answer 60

Basolateral Na⁺/K⁺ ATPases

Question 61

What type of inhibition exists between solutes vying for position with the sodium-solute cotransporters in the PCT lumen?

Answer 61

Competitive inhibition

Question 62

What will happen to PCT reabsorption during ATP-depletion?

Answer 62

It decreases due to decreased Na⁺/K+ activity

Question 63

Normal plasma glucose is about: Normal urine glucose concentrations are about: Glucose is reabsorbed until what concentration?

Answer 63

100 mg/dL 0 mg/dL 375 mg/dL

Question 64

Is most organic anion reabsorbtion in the PCT by passive or active transport? What is the main form of transport used?

Answer 64

**Active**; sodium-linked cotransport (secondary active transport)

Question 65

Is sodium-linked cotransport active or passive transport?

Answer 65

Active (secondary)

Question 66

Is urea actively or passively reabsorbed in the nephron? An increase in what will increase urea excretion (i.e. what will decrease reabsorption)?

Answer 66

Passively; urine flow rate

Question 67

How is phosphate reabsorbed in the PCT?

Answer 67

Actively | (sodium cotransport)

Question 68

What sodium exchanger is present at the PCT basolateral surface? What cotransport is present at the PCT apical surface? What sodium exchanger is present at the PCT apical surface?

Answer 68

Na⁺/K⁺ ATPase Sodium-linked cotransport **Na⁺/H⁺ ATPase**

Question 69

Where does most Cl^- reabsorption happen in the nephron? How?

Answer 69

The _late_ PCT; the Cl^- level builds up and then passively flows down its gradient (between the cells)

Question 70

**True/False**. Na⁺/H⁺ exchangers in the nephron alkalize the tubular lumen and increase bicarbonate reabsorption by making the lumen more positive.

Answer 70

**False**. Na⁺/H⁺ exchangers in the nephron *_acidify_* the tubular lumen and increase bicarbonate reabsorption by making the lumen more *_negative_*.

Question 71

What effect does passive Cl^- reabsorption in the _late_ proximal tubule have on Na⁺ reabsorption?

Answer 71

The tubular lumen becomes more positive, driving Na⁺ out _passively_

Question 72

Sodium reabsorption in the early PCT is: Sodium reabsorption in the late PCT is:

Answer 72

Secondary active (sodium-linked cotransport) Passive (following Cl^- loss)

Question 73

Chloride in the PCT can be exchanged (1:1 exchange) into the tubular cells for any of what three bases?

Answer 73

OH^- HCO₃^- _Formate_

Question 74

In the PCT, chloride ions can be exchanged for bases (formate, OH^-, HCO₃^-). What happens to these bases once they are in the tubule lumen?

Answer 74

They bind hydrogen ions and diffuse back into the cells

Question 75

Bases (OH^-, formate, HCO₃^-) can be exchanged for Cl^- reabsorption in the PCT. H⁺ can be exchanged for Na⁺ reabsorption in the PCT. Are all of these bases and H⁺ then excreted?

Answer 75

No; they combine (neutralizing charge) and diffuse back into the cells

Question 76

Which image depicts NaCl reabsorption in the _early_ PCT? Which image depicts NaCl reabsorption in the _late_ PCT?

Answer 76

2; 1

Question 77

Describe how HCO₃^- is reabsorbed in the PCT at the apical membrane.

Answer 77

Na⁺/H⁺ exchangers pump hydrogen into the tubular lumen. The H⁺ and HCO₃^- form H₂CO₃. Tubular carbonic anhydrase forms CO₂ and H₂O, which then diffuse into the cells. Cellular carbonic anhydrase then recreates HCO₃^-.

Question 78

In the PCT lumen, after HCO₃^- is turned first into H₂CO₃ and then CO₂ / water, what happens next?

Answer 78

The CO₂ and H₂O diffuse into the cell and carbonic anhydrase recreates H₂CO₃. HCO₃^- is then cotransported with Na⁺ and also exchanged for Cl^- at the basolateral cell membrane.

Question 79

Answer 79

A. B. C.

Question 80

**True/False**. The PCT is not very soluble to water.

Answer 80

**False**. It is very soluble to water (via apical and basolateral aquaporins).

Question 81

Why does solute not concentrate in the tubular cells and interstitium as solute is reabsorbed in the PCT?

Answer 81

The capillary movement continuously whisks the solute and fluid away

Question 82

Answer 82

B.

Question 83

You administer 1 L of isotonic saline to a patient. What effect does this have on their blood osmolality?

Answer 83

It decreases | (diluted plasma proteins)

Question 84

Describe the Starling mechanism of the nephron.

Answer 84

If a patient's blood osmolality is low, less fluid will be drawn from the renal interstitium to the capillaries. Fluid builds up in the interstitium, weakening tight junctions and allowing H₂O/Na⁺/Cl^-/HCO₃^- to reenter the PCT lumen for excretion

Question 85

Answer 85

B.

Question 86

What are the two types of nephron (based on anatomical location)? What is the distinction?

Answer 86

Cortical, juxtmedullary (7:1 ratio); the length of their loops of Henle

Question 87

What are the three portions of the loop of Henle?

Answer 87

Thin descending Thin ascending Thick ascending

Question 88

Describe the thin descending loop of Henle.

Answer 88

Highly permeable to H₂O, urea, NaCl, etc. No active NaCl transport

Question 89

Describe the thin ascending loop of Henle.

Answer 89

NO PERMEABILITY TO H₂O Highly permeable to urea, NaCl, etc. No active NaCl transport

Question 90

Describe the thick ascending loop of Henle.

Answer 90

Active NaCl transport No permeability to H₂O

Question 91

Which portion of the loop of Henle is the concentrating portion?

Answer 91

The descending limb (thin)

Question 92

Which portion of the loop of Henle is the diluting portion?

Answer 92

The ascending limb (thin and thick)

Question 93

Where in the loop of Henle can NaCl/urea/solutes be passively reabsorbed? Where in the loop of Henle can H₂O be reabsorbed? Where in the loop of Henle can NaCl be actively reabsorbed?

Answer 93

The entire loop; the descending limb; the thick ascending limb

Question 94

**True/False**. The concentration of the urine is largely decided by activity in the loop of Henle.

Answer 94

**True**.

Question 95

Answer 95

A. B.

Question 96

Answer 96

A. B. C. D.

Question 97

(Select all that apply)

Answer 97

B. D.

Question 98

Answer 98

A. B. C.

Question 99

Describe active reabsorption in the ascending loop of Henle.

Answer 99

**Basolateral membrane:** Na⁺/K⁺ ATPases maintain low Na⁺ in the cell. **Apical membrane:** The Na⁺/Cl^-/K⁺ cotransporter brings in 1 Na⁺, 1 K⁺, and 2 Cl^- all at the same time.

Question 100

What does furosemide do in the nephron? Where?

Answer 100

**Blocks Na-K-Cl cotransport** *in the ascending loop of Henle*

Question 101

What form of passive Na⁺ reabsorption occurs in the thick ascending limb of the loop of Henle?

Answer 101

K⁺ is brought into the cell by Na-K-Cl cotransport. The K⁺ diffuses back out into the lumen via leak channels. The lumen becomes +10 mV. This charge drives Na⁺ out of the lumen via passive, transcellular pathways.

Question 102

(In the nephron)

Answer 102

A. B.

Question 103

Answer 103

A.

Question 104

**True/False**. The renal cortex and medulla have similar intersitial tonicities.

Answer 104

**False**. The medulla is hypertonic when compared with the cortex

Question 105

Why does H₂O passively leave the loop of Henle in the thin descending limb?

Answer 105

It follows the corticomedullary osmolality gradient

Question 106

ADH acts on which portions of the nephron?

Answer 106

The late DCT and the collecting duct

Question 107

Answer 107

A. B. C. D.

Question 108

What is the 'single effect' in the countercurrent multiplier system? What is the single effect osmolality change?

Answer 108

The thick ascending limb pumps Na⁺ out into the intersitium, diluting the fluid sent to the DCT *(in the image, loop of Henle 1 is basically being turned into loop of Henle 2)*; this is a ~200 mOsm/kg difference.

Question 109

Answer 109

A. C. D.

Question 110

Answer 110

A. B. C.

Question 111

At its deepest point, what is the osmolality of the lumen of the loop of Henle? At its deepest point, what is the osmolality of the vasa recta?

Answer 111

1200 mOsm/kg 1200 mOsm/kg

Question 112

Answer 112

C. D.

Question 113

What three solutes play the biggest role in urine concentration?

Answer 113

Na⁺, Cl^-, and urea

Question 114

Where are the only locations in the nephron where urea reabsorption occurs?

Answer 114

The PCT (50%); the collecting duct of the inner medulla

Question 115

Is urea reabsorbed in the outer medullary portion or the inner medullary portion of the collecting duct?

Answer 115

Inner medullary portion

Question 116

**True/False**. Some urea that is reabsorbed in the collecting duct (in the inner medullary portion) will be secreted into the loop of Henle to affect countercurrent multiplication.

Answer 116

**True**.

Question 117

**True/False**. Urea is responsible for 40% of medullary interstitial osmolality, meaning that the higher NaCl concentration in the loop of Henle provide a chemical gradient to drive NaCl out into the interstitium, even though the intersititum's total osmolality is higher.

Answer 117

**True**.

Question 118

Answer 118

A. B. C.

Question 119

Where is the macula densa located?

Answer 119

At the **junction** of the (1) thick ascending limb of the loop of Henle and (2) the DCT

Question 120

What are the two halves of the distal tubule of the nephron?

Answer 120

The early D.T. (DCT) and the late D.T. (connecting tubule)

Question 121

What is the main purpose of the early distal tubule of the nephron? What is the main purpose of the late distal tubule of the nephron?

Answer 121

NaCl reabsorption; NaCl and H₂O reabsorption

Question 122

What type(s) of cell line(s) the early distal tubule of the nephron? What are the functions? What type(s) of cell line(s) the late distal tubule of the nephron? What are the functions?

Answer 122

Distal tubule cells (NaCl reabsorption); connecting tubule cells (NaCl + H₂O reabsorption), intercalated cells (H⁺ secretion)

Question 123

1. What type of cell in the distal tubule is responsible for NaCl and H₂O reabsorption? Early or late distal tubule? 2. What type of cell in the distal tubule is responsible for only H⁺ secretion? Early or late distal tubule? 3. What type of cell in the distal tubule is responsible for only NaCl reabsorption? Early or late distal tubule?

Answer 123

Collecting tubule cells (late, 75% of late); intercalated cells (late, 25% of late); distal convoluted cells (early, 100% of early)

Question 124

What are the three sections of the collecting duct in the nephron?

Answer 124

Cortical, outer medullary, inner medullary

Question 125

What are the two main cell types in the collecting duct? Describe the changes in cell type concentrations found in the cortical CD vs. the outer medullary CD vs. the inner medullary CD.

Answer 125

Principal cells; intercalated cells * (CCD - 75:25* * OMCD - 80:20* * IMCD - 99:1)*

Question 126

What is the function of collecting duct principal cells? What is the function of collecting duct intercalated cells?

Answer 126

NaCl and H₂O reabsorption, K⁺ secretion; H⁺ secretion

Question 127

Via what mechanism do distal convoluted cells absorb NaCl?

Answer 127

Apical Na⁺/Cl^- cotransport; basolateral Na⁺/K⁺ ATPases

Question 128

What type of transmembrane protein structure is abundant on the basolateral membranes of cells of the nephron? It maintains intracellular Na⁺ concentrations at a very ____ level.

Answer 128

Na⁺/K⁺ ATPases; low

Question 129

How do thiazide diuretics (e.g. hydrochlorothiazide) affect the kidney?

Answer 129

They block Na⁺/Cl^- cotransport in the early distal convoluted tubule

Question 130

Answer 130

C. ## Footnote *(remember, these are separate from the connecting tubule cells and intercalated cells of the late distal tubule)*

Question 131

Describe the electrolyte transport of \*collecting tubule cells (late distal tubule) and \*principal cells (of the collecting duct). *\*Note: these can be considered virtually identical for our purposes.*

Answer 131

(Note: chloride is reabsorbed through the transcellular space)

Question 132

Where does potassium secretion occur in the nephron? Via what type(s) of cell? In exchange for what ion?

Answer 132

The late distal tubule and collecting duct; collecting tubule cells, principal cells; Na⁺

Question 133

Describe the ion transport of intercalated cells in the nephron.

Answer 133

Question 134

**True/False**. Chloride reabsorption in the nephron often follows sodium reabsorption because the loss of sodium leaves a slightly positive charge in the tubules.

Answer 134

**False**. Cl^- reabsorption in the nephron often follows Na⁺ reabsorption because the loss of Na⁺ leaves a slightly *_negative_* charge in the tubules.

Question 135

Answer 135

B.

Question 136

ADH causes water reabsorption in what tubules?

Answer 136

The collecting tubule (late distal tubule) and the collecting duct

Question 137

Why does urea leave the collecting duct to the inner medulla?

Answer 137

ADH concentrates the fluid so there is a high [Urea] the time it reaches the inner medulla portion

Question 138

*In the late distal tubule and the collecting duct*

Answer 138

A. B.

Question 139

What are the three mechanisms regulating late distal tubule and collecting duct Na⁺ reabsorption?

Answer 139

1. Tubular flow 2. Plasma [K⁺] 3. Aldosterone

Question 140

Why can drugs like furosemide cause hypokalemia?

Answer 140

Furosemide increases loop of Henle tubular Na⁺, thus increasing K⁺ secretion in the late distal tubule and collecting duct (see principal cells in image)

Question 141

Describe the tubular flow mechanism regulating late distal tubule and collecting duct Na+ reabsorption.

Answer 141

Since this portion utilizes Na⁺ and K⁺ leak channels, increased Na⁺ delivery (increased tubular flow) causes increased Na⁺ reabsorption and K⁺ secretion

Question 142

Describe the plasma [K⁺] mechanism regulating late distal tubule and collecting duct Na+ reabsorption.

Answer 142

Increased plasma [K⁺] causes increased basolateral Na⁺/K⁺ ATPase activity and increased Na⁺ reabsorption and K⁺ secretion

Question 143

Describe the aldosterone mechanism regulating late distal tubule and collecting duct Na⁺ reabsorption.

Answer 143

(1) Increased insertion of Na⁺ channels into the apical membrane; (2) increased insertion of Na⁺/K⁺ ATPases into the basolateral membrane

Question 144

How does aldosterone get into the renal cells? Its effects are then on ________ receptors.

Answer 144

Simple diffusion (its a steroid hormone); nuclear (affecting transcription)

Question 145

Answer 145

A. B. C.

Question 146

Answer 146

D.

Question 147

Answer 147

A. D.

Question 148

What makes ADH and oxytocin so similar that they are both synthesized in the hypothalamus (paraventricular and supraoptic nuclei)?

Answer 148

Their structures are very similar.

Question 149

What receptor does ADH bind on the basolateral surface of nephron cells? What is the effect?

Answer 149

V₂; protein phosphorylation and aquaporin₂ insertion into the apical membrane

Question 150

Which aquaporin is inserted into the apical membrane of the collecting tubule and collecting duct when ADH is present? Which aquaporins are present on the basolateral membrane regardless of ADH presence?

Answer 150

Aquaporin₂; aquaporin₃, aquaporin₄

Question 151

Answer 151

A. C. D.

Question 152

What are the main two factors regulating ADH release?

Answer 152

1. **P****lasma osmolality** (hypothalamic osmoreceptors) 2. **Blood volume** (atrial stretch receptors)

Question 153

Answer 153

C.

Question 154

Answer 154

A. E.

Question 155

What is the major mediator of the effects of the renin-angiotensin system?

Answer 155

Angiotensin II

Question 156

Besides the pulmonary circulation, where is another location where ACE is located?

Answer 156

The basolateral surface of renal cells

Question 157

**True/False**. Most angiotensinogen is produced by the PCT, but some is also produced in the liver.

Answer 157

**False**. Most angiotensinogen is produced by the _liver_, but some is also produced in the _PCT_.

Question 158

Angiotensin II primarily acts on ___ receptors. AT2 receptors are primarily involved in:

Answer 158

AT1; renal development

Question 159

**True/False**. A fraction of bodily angiotensin II can be produced completely within the kidney without any hepatic or pulmonary or circulatory involvement.

Answer 159

**True**. Some angiotensinogen is produced in the renal interstitium, and ACE can be found on the basolateral epithelial surface.

Question 160

What cell type produces renin?

Answer 160

Juxtaglomerular cells

Question 161

What is the rate-limiting factor of the renin-angiotensin system?

Answer 161

Renin production

Question 162

Answer 162

A. B. C.

Question 163

Name the four major activating mechanisms for renin secretion.

Answer 163

(First row)

Question 164

Name the three mechanisms for increasing renin secretion.

Answer 164

(Second row)

Question 165

What happens in the juxtaglomerular cells for renin to be secreted?

Answer 165

(Third row)

Question 166

Answer 166

A. B. C. D.

Question 167

Answer 167

C.

Question 168

Answer 168

C.

Question 169

**True/False**. Angiotensin II has many diverse actions.

Answer 169

True.

Question 173

Answer 173

A. B. C.

Question 179

What renal mechanism senses increased renal arteriolar stretch? What is the result?

Answer 179

Baroreceptors in juxtaglomerulus (calcium channels opened); _inhibition_ of renin release

Question 180

Answer 180

A.

Question 181

Answer 181

C.

Question 182

Answer 182

A. B. C. D. E.

Question 183

What effect does increased sympathetic tone have on juxtaglomerular cells?

Answer 183

β₁ activation --\> cAMP --\> **increased renin secretion**

Question 184

What effect does an increase in NaCl delivery to the macula densa have on the juxtaglomerular cells? Why?

Answer 184

Decreased renin secretion; the JG cells interpret this as increased ECF *(maybe mediated via PGE₂)*

Question 186

What effect does a decrease in NaCl delivery to the macula densa have on the juxtaglomerular cells? Why?

Answer 186

Increased renin secretion; the JG cells interpret this as decreased ECF *(maybe mediated via PGE₂)*

Question 187

Name the major functions of angiotensin II in the following systems: *renal, adrenal, blood vessels, heart, intestines, CNS, PNS*.

Answer 187

1. **Renal**: Reduce RBF, increase NaCl reabsorption 2. **Adrenal**: Aldosterone release 3. **BV**: Vasoconstriction 4. **Heart**: Cardiac contractility 5. **Intestine**: NaCl + H₂O reabsorption 6. **CNS**: Thirst, salt appetite, ADH release 7. **PNS**: Sympathetic activity

Question 188

What effect (if any) does angiotensin II have on the renal arterioles? What effect (if any) does angiotensin II have on the K_f?

Answer 188

Efferent arteriole constriction (with no change in GFR); it decreases it (mesangial contraction)

Question 189

What parts of the nephron are stimulated to reabsorb NaCl by angiotensin II?

Answer 189

The PCT and DCT

Question 190

What overall effect does angiotensin II have on the GFR? How?

Answer 190

It maintains it; efferent arteriole constriction

Question 191

**True/False**. Increases in Na⁺ retention via aldosterone will also result in an increase in K⁺ loss.

Answer 191

True.

Question 195

What are the major prostaglandins produced in the kidney?

Answer 195

PGE₂ PGI₂ (prostacyclin) Thromboxane A₂

Question 196

What are the major vasodilating prostaglandins produced by the kidney? What do they dilate?

Answer 196

PGI₂ (prostacyclin), PGE₂; **both** the afferent and efferent arterioles

Question 197

What effect do renal prostaglandins have on GFR? Which arterioles do they affect? How? How do they affect NaCl reabsorption?

Answer 197

Virtually no effect; both afferent and efferent, dilation; decreased

Question 198

When are renal prostaglandins produced? Why?

Answer 198

When ECF and MAP are decreased; to **counteract** angiotensin II, norepinephrine, ADH, etc.

Question 199

What hormone(s) promote(s) renal arteriolar dilation? Which arterioles? What hormone(s) promote(s) renal arteriolar constriction? Which arterioles?

Answer 199

PGE₂, PGI₂, bradykinin, afferent and efferent; angiotensin II, efferent

Question 200

Along with prostaglandin production, renal __________ helps counteract angiotensin II.

Answer 200

Bradykinin

Question 201

\_\_\_\_\_\_\_\_\_\_\_ digests high-molecular weight ____________ to produce bradykinin.

Answer 201

Kallikrein; kininogen

Question 202

Where is renal kallikrein found?

Answer 202

The renal collecting tubule (late DCT)

Question 203

How does bradykinin exert an effect on the kidney?

Answer 203

By binding B₂ receptors --\> increase NO, PGE₂, and PGI₂ secretion

Question 204

Upon carbonic anhydrase creation of bicarbonate in the PCT cells, what happens to the bicarbonate next?

Answer 204

Basolateral co-transport of 3 HCO₃^- to every 1 Na⁺; also, HCO₃^-/Cl^- exchangers

Question 205

How does acetazolamide affect the kidneys?

Answer 205

**Increased HCO₃^- excretion** via blockage of lumen carbonic anhydrase

Question 206

What is a normal blood pressure? What is an elevated blood pressure?

Answer 206

\<120 / \<80 mmHg 120 - 129 / \<80 mmHg

Question 207

What is hypertension stage I? What is hypertension stage II?

Answer 207

**130-139** mmHg SBP OR **80-89** mmHg DBP **≥ 140** mmHg SBP OR **≥ 90** mmHg DBP

Question 208

What BP defines a hypertensive crisis?

Answer 208

≥ 180 mmHg SBP OR ≥ 120 mmHg DBP

Question 209

**True/False**. Hypertension can cause (among other effects): stroke, heart attack, retinopathy, peripheral vascular disease, renal failure, left ventricular hypertrophy, congestive heart failure, etc.

Answer 209

True.

Question 210

What is malignant hypertension?

Answer 210

≥ 200 mmHg SBP and ≥ 100 mmHg DBP

Question 211

**True/False**. Excess salt intake is often accompanied by little-to-no elevation in plasma sodium levels.

Answer 211

True.

Question 212

**True/False**. Many monogenetic causes of hypertension have been identified in the kidneys.

Answer 212

True.

Question 213

**True/False**. Sodium excretion has little to do with hypertension reduction in sodium-replete states.

Answer 213

False.

Question 214

**True/False**. Loss of alkali can occur via the kidneys and GI tract.

Answer 214

**True**.

Question 215

Loss of ______ (pH) substances often occurs due to diarrhea. Loss of ______ (pH) substances often occurs due to vomiting or nasogastric tube usage.

Answer 215

Alkaline; acidic

Question 216

What is the principal mechanism for renal acid buffering?

Answer 216

Phosphate secretion *(Net acid excretion = titratable acid + NH₄⁺ - HCO₃^-)*

Question 217

**True/False**. Daily renal pH excretion is typically about 70 mEqv of base.

Answer 217

**False**. Daily renal pH excretion is typically about 70 mEqv of _acid_. *(And a resultant 70 mEqv of carbonic acid created to buffer/replace it)*

Question 220

What effect do angiotensin II, glucocorticoids, and endothelin have on HCO₃^- renal reabsorption?

Answer 220

All increase reabsorption

Question 221

In the collecting tubule and duct, type A intercalated cells do what? In the collecting tubule and duct, type B intercalated cells do what?

Answer 221

Secrete H⁺, reabsorb HCO₃^-; secrete HCO₃^-

Question 222

**True/False**. H⁺ secretion in the nephron can be through H⁺/K⁺ exchange, H⁺/Na⁺ exchange, and H⁺ ATPases.

Answer 222

True.

Question 223

What is the major acid of urine excretion? What is the major buffer of urine excretion?

Answer 223

NH₄⁺; PO₃^-

Question 224

**True/False**. Excretion of NH₄⁺ corresponds exactly with creation of HCO₃^-.

Answer 224

**True**. Both are made from glutamine.

Question 225

**True/False**. Very small increases in plasma K⁺ can be deadly.

Answer 225

**True**.

Question 226

If a person ingests their daily quantity of potassium in just a few minutes (~100 mEq/day), are they at risk for cardiac complications?

Answer 226

No, this ingested K⁺ is quickly moved to the intracellular fluid

Question 227

What is the initial defense against hyperkalemia?

Answer 227

Uptake into cells (often via insulin, osmolality, β-adrenergic effects)

Question 228

What cell type in the nephron is responsible for K⁺ secretion?

Answer 228

Collecting tubule cells / principal cells

Question 229

What are some easy methods by which you can check for ECF volume depletion in a patient?

Answer 229

Tachycardia; hypotension (may be orthostatic); skin turgor (variable); dry mucus membranes (variable)

Question 230

Total body __ determines ECF volume.

Answer 230

Na⁺

Question 231

A patient that has been vomiting presents with a HCO₃^- of 35 and a K⁺ of 3.0. What explains this finding? Why don't they just urinate out the excess bicarbonate? How do you treat them?

Answer 231

The ECF volume is depleted *(regulatory mechanisms are reabsorbing all the Na⁺, H₂O, and HCO₃^-; Na⁺ can be in exchange for K⁺ and H⁺)*; IV saline (correct the ECF depletion and the alkalosis will resolve itself)

Question 232

What effect does Conn's syndrome usually have on Na⁺ levels? What effect does Conn's syndrome usually have on pH levels? What effect does Conn's syndrome usually have on K⁺ levels?

Answer 232

Not much; alkalemia; decrease

Question 233

What happens when plasma Na⁺ levels rise?

Answer 233

ADH is released to increase H₂O reabsorption ## Footnote *(diluting the Na⁺ and maintaining osmolality)*

Question 234

How would an ADH-secreting small cell carcinoma of the lung present on laboratory findings?

Answer 234

Low osmolality; normal BP; lowered plasma Na⁺

Question 235

Do relatively small changes in blood volume affect ADH secretion?

Answer 235

No.

Question 236

What are the three ionic main effects of aldosterone?

Answer 236

Na⁺ reabsorption K⁺ secretion H⁺ secretion