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Physiology Exam III Material > Renal Acid Base Regulation > Flashcards

Renal Acid Base Regulation Flashcards

1
Q

Acids are compounds that release

A

H+ ions

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2
Q

_____ dissociate completely

A

Strong Acids

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3
Q

_____ do not dissociate completely and dissociate into hydrogen ions (H+) and conjugate base

A

Weak acids (conjugate acid)

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4
Q

Compounds that accept H+ ions

A

Bases

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5
Q

What are the two types of acids produced in the body

A
  • Volatile Acids

- Nonvolatile Acids (fixed acids)

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6
Q

Volatile acid are excreted from the ____

A

lungs

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7
Q

Carbon dioxide is a _____ acid

A

Volatile

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8
Q

Carbon dioxide is a product of

A

cellular aerobic metabolism

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9
Q

CO2 + H2O —->

A

H2CO3

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10
Q

H2CO3 —->

A

H+ + HCO3-

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11
Q

Carbonic anhydrase catalyzes

A

H2O + CO2—-> H2CO3
and
H2CO3—–> HCO3- + H+

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12
Q

Nonvolatile acids (fixed acids) are excreted from

A

kidneys

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13
Q

Examples of Nonvolatile acids (fixed acids)

A
  • Sulfuric acid (product of protein catabolism)
  • Phosphoric acid (product of phospholipid catabolism)
  • Ketoacids, lactic acid, salicylic acid
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14
Q

sulfuric acid is a product of

A

protein catabolism

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15
Q

Phosphoric acid is a product of

A

phospholipid catabolism

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16
Q

pH=

A

pH= -log{H+}

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17
Q

Arterial blood pH range

A

7.37-7.44

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18
Q

Venous blood pH range

A

7.35-7.45

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19
Q

The greater the hydrogen ion concentration, the ____ the pH

A

Lower

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20
Q

____ is the equilibrium constant for the dissociation reaction

A

Ka

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21
Q

The major systems regulating [H+]

A
  • Chemical acid-base systems of the body fluid
  • Respiratory center
  • Kidneys
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22
Q

Henderson-Hasselbalch Equation

A

pH= pKa + log [A-]/ [HA]

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23
Q

A _____ is a substance that can reversibly bind H+

A

buffer

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24
Q

a buffer consists of a

A

weak acid (HA)=conjugate acid

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25
Q

What are the 3 buffer systems

A
  • bicarbonate buffer system
  • Phosphate buffer system
  • proteins as buffer
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26
Q

Bicarbonate buffer system consists of

A
  • a weak acid: H2CO3

- A bicarbonate salt: NaHCO3

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27
Q

CO2+H2o—-> H2CO3 is catalyzed by

A

carbonic anhydrase

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28
Q

when a strong acid is added to the bicarbonate buffer system _____ is formed

A

a weak acid

ex. H+ + HCO3- —-> CO2 +H2O

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29
Q

Addition of a strong base to bicarbonate buffer system leads to the formation of

A

a weak base

  • NaOH+ H2CO3—-> NaHCO3 + H2O
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30
Q

The increased levels of HCO3- can be excreted via the

A

kidneys

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31
Q

What is the most important extracellular buffer system

A

Bicarbonate Buffer System

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32
Q

Bicarbonate concentration is regulated mainly by the

A

kidneys

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33
Q

pCO2 is controlled by rate of

A

respiration

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34
Q

a pH of ____ occurs when concentrations of both bicarbonate ions and carbon dioxide are equal

A

6.1 ( note that at this point pH= pKa of the buffer system)

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35
Q

Plays a major role in buffering renal tubular fluid and intracellular fluids

A

Phosphate Buffer system

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36
Q

What are the two reasons for phosphate buffer systems importance as a buffer in kidney tubular fluids

A
  • Usually becomes greatly concentrated in tubules

- Lower pH of the tubular fluid brings the operating range of the buffer closer to the pK of the buffer system

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37
Q

What are the main elements of the phosphate buffer system

A

H2PO4- , HPO4

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38
Q

In the phosphate buffer system strong acids is replaced by

A

an additional amount of weak acid and pH change is minimal

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39
Q

kidneys can excrete either acidic or basic urine how

A
  • Large numbers of bicarbonate ions are filtered continuously into the tubule, and if they are excreted this removes base form the blood
  • Large numbers of hydrogen ions can be secreted into the tubular lumen
40
Q

The primary method for removing nonvolatile acids is through

A

renal excretion

41
Q

Almost all filtered bicarbonate is ______, but it must react with secreted hydrogen ion to form _____ before it can be _______.

A

reabsorbed, carbonic acid, reabsorbed

42
Q

_____ mEq of hydrogen ion must be secreted each day just to reabsorb the ______ mEq of filtered bicarbonate

A

4320mEq, 4320 mEq

43
Q

Mechanisms for regulating extracellular H+

A
  • kidneys reabsorb filtered bicarbonate ions
  • kidneys can secrete hydrogen ions
  • Kidneys produce new bicarbonate ions
44
Q

What percent of bicarbonate is reabsorbed in the proximal convoluted tubule

A

85%

45
Q

What % of bicarbonate is reabsorbed in the thick ascending loop of Henle

A

10%

46
Q

What percent of bicarbonate is reabsorbed in the distal tubule and collecting duct

A

about 4.9%

47
Q

Explain the mechanism of Bicarbonate reabsorption in the proximal, thick ascending, and early distal tubule

A

Secondary active transport via H+-Na antiporter

The secretory process begins when CO 2 either diffuses into the tubular cells or is formed by metabolism in the tubular epithelial cells. CO 2 , under the influence of the enzyme carbonic anhydrase, combines with H 2 O to form H 2 CO 3 , which dissociates into HCO 3 − and H + . The H + is secreted from the cell into the tubular lumen by sodium-hydrogen counter-transport. That is, when Na + moves from the lumen of the tubule to the interior of the cell, it first combines with a carrier protein in the luminal border of the cell membrane; at the same time, a H + in the interior of the cells combines with the carrier protein. The Na + moves into the cell down a concentration gradient that has been established by the sodium-potassium ATPase pump in the basolateral membrane. The gradient for Na + movement into the cell then provides the energy for moving H + in the opposite direction from the interior of the cell to the tubular lumen. The HCO 3 − generated in the cell (when H + dissociates from H 2 CO 3 ) then moves downhill across the basolateral membrane into the renal interstitial fluid and the peritubular capillary blood. The net result is that for every H + secreted into the tubular lumen, an HCO 3 − enters the blood.

48
Q

How is H+ secreted in the late distal and collecting tubules

A

Primary active secretion of H+ in the intercalated cells

It occurs at the luminal surface of the tubular cells, where H+ is transported directly by specific proteins, a hydrogen-transporting ATPase and a hydrogen potassium-ATPase transporter

Hydrogen ion secretion is accomplished in two steps

  • 1.) the dissolved CO2 in this cell combines with H2O to form H2CO3
  • 2.) The H2CO3 then dissociates into HCO3-, which is reabsorbed into the blood, plus H+, which is secreted into the tubule by means of the hydrogen-ATPase transporters.

note that one HCO3- is absorbed for each H+ secreted,and one chloride ion is passively secreted along with H+

49
Q

Although the secretion of H+ in the late distal tubule and collecting tubules accounts for only about 5 percent of the total H+ secreted, this mechanism is important in

A

forming maximally acidic urine

50
Q

What is the transporter in Type A intercalated cells that allows HCO3- to enter the renal interstitial fluid

A

HCO3- - Chloride exchanger

51
Q

Where in the kidney tubules does hydrogen ion secretion and bicarbonate reabsorption occur

A
  • Hydrogen ion secretion via secondary active transport (coupled with sodium ion transport) occurs in almost all parts of the tubules except the descending and ascending thin limbs of the loop of henle
  • Primary active hydrogen secretion begins in the late distal tubules in the intercalated cells and involves a hydrogen-transporting ATPase and Hydrogen-potassium ATPase transporter
52
Q

Primary active hydrogen secretion begins in the ____ and involves a ______ and ______

A

Late distal tubules in intercalated cells,hydrogen-transporting ATPase and hydrogen-potassium ATPase transporter

53
Q

Bicarbonate reabsorption is initiated by a reaction in the tubules between bicarbonate ion filtered at the glomerulus and hydrogen ion secreted by the _____. This results in the formation of ______ which then dissociates into carbon dioxide and water

A

tubular cells, Carbonic acid

54
Q

Carbon dioxide diffuses into the tubular cells where it recombines with water to generate a new ______ which then dissociates to form ____ and ____

A

Carbonic acid molecule, bicarbonate ion, hydrogen ion

55
Q

The bicarbonate ion diffuses through the basolateral membrane into the ______ fluid and then into the ___

A

interstitial fluid, blood

56
Q

______ is necessary for the formation of carbonic acid from carbon dioxide and water

A

Carbonic anhydrase

57
Q

The bicarbonate ion taken up by the pericapillary tubules is formed from the dissociation of _______ into hydrogenion and bicarbonate ion.

A

carbonic acid

58
Q

Is the bicarbonate ion taken up by the pericapillary tubules the same as the one that is filtered into the tubular lumen

A

No

59
Q

Explain the use of incomplete titration to correct acidosis or alkalosis

A
  • Normally each time a hydrogen ion is formed in the tubular epithelial cells, a bicarbonate ion is also formed and released back into the blood
  • In metabolic acidosis new bicarbonate ion is added to the extracellular fluid
  • in metabolic alkalosis, bicarbonate ions are removed form extracellular fluid by renal excretion
60
Q

Active transport resulting in hydrogen ion secretion is carried out by

A

intercalated cells

61
Q

2-step process of hydrogen ion secretion in intercalated cells

A
  • Dissolved carbon dioxide in intercalated cells combines with water to form carbonic acid
  • The carbonic acid then dissociates into bicarbonate, which is rapidly reabsorbed into the blood, and hydrogen ion, which is secreted into the tubular lumen by means of the hydrogen-ATPase transporters
62
Q

What is the lower limit of pH that can be achieved in normal kidneys

A

4.5

63
Q

Hydrogen ion secretion in the proximal tubule (and other areas of the renal tubule) occurs via __________

A

secondary sodium-hydrogen countertransporter

64
Q

The sodium-hydrogen exchangers are located on the _________ of the renal epithelial cells

A

apical (luminal) membranes

65
Q

Sodium-potassium ATPase exchangers are found on the ________ of renal epithelial cells

A

basal membranes

66
Q

Each day the body produces about _____ mEq of nonvolatile acids, mostly from the metabolism of proteins. because these are nonvolatile acids, they cannot be excreted by the _____. They are primarily removed via ______

A

80mEq, Lungs, They are primarily removed via renal excretion

67
Q

The loss of bicarbonate ions in the extracellular fluid is the same as

A

adding hydrogen ions to the Extracellular fluid

68
Q

Only a small part of the excess hydrogen ion secreted in excess of the filtered bicarbonate ion can be excreted in ionic form in the ____

A

urine

69
Q

why can only a small part of the excess hydrogen ion secreted in excess of the filtered bicarbonate ion be excreted in ionic form in the urine

A

Because the minimal urine pH is about 4.5 (H+ concentration= 10^-4.5 mEq/L or 0.03 mEq/L)

70
Q

To excrete the 80mEQ of nonvolatile acid formed by metabolism per day, about _____ liters of urine would have to be excreted if all the excess hydrogen ion remained free in solution

A

2667 (80/minimal urine pH, which is equal to 0.03mEq/L of H+)

71
Q

What buffers are important in allowing larger amounts of hydrogen ion to be excreted

A
  • Phosphate buffer system

- Ammonia buffer system

72
Q

excess hydrogen ions are eliminated through binding with _____ or _____ ions

A

phosphate or ammonia

73
Q

What is new bicarbonate ion

A

when hydrogen ions are combining with other buffers in the tubular lumen, then excess bicarbonate ion is available to be returned to the blood. This is new bicarbonate ion

74
Q

Where are intercalated cells found

A

Only in the late distal tubules

75
Q

What are intercalated cells role in hydrogen ion transport

A

They actively transport Hydrogen ions into the tubular lumen using hydrogen ATPase transporters.

This leads to the acidic concentration of urine

76
Q

Reduction in extracellular fluid hydrogen ion concentration leads to

A

alkalosis

77
Q

Kidneys can correct ____ by failing to reabsorb all the filtered bicarbonate ion (this is the same as adding hydrogen ion to the extracellular fluid)

A

alkalosis

78
Q

kidneys can correct alkalosis by

A

failing to reabsorb all the filtered bicarbonate ion (this is the same as adding hydrogen ion to the extracellular fluid)

79
Q

_____ occurs when the ratio of bicarbonate ion to carbon dioxide n extracellular fluid decreases

A

Acidosis

80
Q

Metabolic acidosis

A

Decrease in bicarbonate ion

81
Q

Respiratory acidosis

A

Increase in carbon dioxide

82
Q

What is the primary compensatory response for respiratory acidosis

A

increase in plasma bicarbonate ion due to addition of new bicarbonate by the kidney

83
Q

Primary compensatory response metabolic acidosis

A
  • Increased ventilation rate

- Renal compensation: adds new bicarbonate ion to extracellular fluid

84
Q

Respiratory alkalosis occurs when there is a decrease in

A

carbon dioxide concentration

85
Q

Respiratory alkalosis can be caused by

A
  • caused by hyperventilation
86
Q

Compensatory response of respiratory alkalosis

A

-Reduction in plasma bicarbonate ion concentration caused by renal excretion of bicarbonate ion

87
Q

Metabolic alkalosis is caused by a rise

A

extracellular fluid bicarbonate ion concentration

88
Q

What are the compensatory response for metabolic alkalosis

A
  • Decreased ventilation

- Increased renal bicarbonate ion excretion

89
Q

What is the most important buffering system for renal tubular fluid

A

Phosphate buffer system

90
Q

Compounds that dissociate incompletely into hydrogen ions and a conjugate base are made of compounds

A
  • Weak acids
91
Q

The bicarbonate buffer system consists of bicarbonate and what

A

A weak acid

92
Q

Primary active hydrogen secretion involves a hydrogen transporting ATPase. It occurs in which of the following parts of the renal tubules?

  • A.) Descending limb of Henle
  • B.) Ascending limb of Henle
  • C.) Late distal tubules in intercalated cells
  • D.) Early collecting in principle cells
A

C.) Late distal tubules in intercalated cells

93
Q

Most bicarbonate reabsorption occurs in which of the following parts of the renal tubule?

A.) Proximal tubule
B.) Descending limb of Henle
C.) Ascending limb of Henle
D.) Distal tubule

A
  • Proximal Tubule
94
Q

Which of the following occurs when a decrease in bicarbonate ion results in a decrease in the ratio of bicarbonate ion to carbon dioxide in the extracellular fluid?

A.) Respiratory Acidosis
B.) Respiratory Alkalosis
C.) Metabolic Acidosis
D.) Metabolic Alkalosis

A

Metabolic Acidosis

95
Q

Respiratory alkalosis due to a decrease in carbon dioxide concentration caused by hyperventilation is compensated for by which of the following mechanisms?

A.) Increased Ventilation Rate
B.) Decreased Ventilation Rate
C.) Renal Excretion of bicarbonate ion
D.) Renal addition of new bicarbonate ion to extracellular fluid

A

C.) Renal excretion of bicarbonate ion

Physiology Exam III Material (13 decks)

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