Renal Acid Base Regulation

Question 1

What is a base?

Answer 1

A compound that accepts hydrogen ions.

Question 2

What is a volatile acid, and what organ is it excreted from?

Answer 2

carbon dioxide is a volatile acid. It is a product of aerobic respiration and is excreted from the lungs.

Question 3

What is a nonvolatile acid, and where is excreted from?

Answer 3

sulfuric acid, phosphoric acid, ketoacids, lactic acid, salicylic acid. It is excreted from the kidneys.

Question 4

What is pH?

Answer 4

-log[H+].

Question 5

You take a blood sample from a healthy patient. What do you expect the pH of the blood (arterial and venous) to be?

Answer 5

arterial: 7.37 - 7.44
Venous: 7.35 - 7.45

Question 6

What is the equilibirum constant for the dissociation reaction?

Answer 6

K = [H+][A-]/[HA]

Question 7

When determining the pH of blood, what does the pKa value represent?

Answer 7

the dissociation constant of carbonic acid in water (6.1).

Question 8

You take a blood sample from a healthy patient. What do you expect the pH of their blood pressure to be?

Answer 8

7.4

Question 9

What three major systems regulate [H+]?

Answer 9

Chemical acid-base buffer systems of body fluids

Respiratory center

Kidneys

Question 10

What is a buffer?

Answer 10

A substance that can reversibly bind H+.

Question 11

What are the three important buffer systems in the body?

Answer 11

bicarbonate

Phosphate

proteins

Question 12

Which buffer system is the most important extracellular system?

Answer 12

bicarbonate buffer system.

Question 13

When a strong acid is added to the bicarbonate buffer system, what is formed?

Answer 13

A weak acid.

Question 14

When a strong base is added to the bicarbonate buffer system, what is formed?

Answer 14

A weak base.

Question 15

What organ primarily regulates the bicarbonate buffer system?

Answer 15

the kidneys

Question 16

As carbon dioxide decreases in the biccarbonate buffer system, what subsequently decreases?

Answer 16

Respiration and carbon dioxide expiration.

Question 17

You encounter a patient who is experiencing metabolic acidosis. What ion is most likely affected?

Answer 17

bicarbonate; it is LOW in the extracellular fluid.

Question 18

You encounter a patient who is experiencing metabolic alkalosis. Do you expect extracellular bicarbonate levels to be low or high?

Answer 18

HIGH

Question 19

You encounter a patient who is suffering from respiratory acidosis. Do you expect levels of carbon dioxide to be low or high?

Answer 19

HIGH

Question 20

You encounter a patient who is suffering from respiratory alkalosis. Do you expect their carbon dioxide levels to be low or high?

Answer 20

LOW

Question 21

You encounter a patient who has a respiratory disorder. You note that they have a low pCO2 value. Are they suffering from respiratory acidosis or alkalosis?

Answer 21

ALKALOSIS

Question 22

How does the normal operating pH point for the bicarbonate buffer system compare to its pKa?

Answer 22

The normal operating point has a higher pH (7.4) and has a greater level of buffer (HCO3). The buffer has a much lower pH (6.1) and has equal amounts of carbonic acid, bicarbonate and carbon dioxide.

Question 23

The phosphate buffer system plays a major role in buffering what fluid?

Answer 23

Renal tubular fluid.

Question 24

The phosphate buffer system is important because phosphate usually becomes greatly concentrated in the tubules. What is another reason why the phosphate buffer system is important in the kidneys?

Answer 24

The phosphate buffer system lowers the pH of tubular fulid, bringing the operating range of the buffer closer to the pKa of the buffer system.

Question 25

What is the primary method for removing nonvolatile acids?

Answer 25

Through renal excretion.

Question 26

What must happen before bicarbonate is reabsorbed?

Answer 26

It must react with secreted hydrogen ion to form carbonic acid before it can be reabsorbed.

Question 27

How much of the hydrogen ion must be secreted to reabsorb 4320 mEq of filtered bicarbonate?

Answer 27

4320 mEq

Question 28

What are the three mechanisms by which the kidneys regulate extracellular hydrogen ions?

Answer 28

Kidneys reabsorb filtered bicarbonate ions Kidneys can secrete hydrogen ions Kidneys produce new bicarbonate ions.

Question 29

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

Answer 29

The majority of bicarbonate reabsorption occurs in the proximal convoluted tubule. Hydrogen ion secretion via secondary active transport occurs in all parts of the tubules except the descending and ascending limbs of the loop of Henle.

Question 30

How is a bicarbonate ion reabsorbed?

Answer 30

It is initially broken down in the lumen (becomes carbon dioxide and water) and diffuses across the tubular cells. The carbon dioxide then reacts with water in the cell to make bicarbonate before it is actively transported (via a symporter) into the interstitial fluid.

Question 31

What role does carbonic anhydrase play in reabosrbing bicarbonate?

Answer 31

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

Question 32

Why is the bicarbonate ion returned to the extracellular fluid not the same as that filtered idnto the tubular lumen?

Answer 32

The bicarbonate dissociates in the lumen and reforms in the tubular cells.

Question 33

How is the bicarbonate ion normally titrated against hydrogen ions?

Answer 33

Each time a hydrogen ion is formed in the tubular epithelial cells, a bicarbonate ion is also formed and released back into the blood.

Question 34

How is incomplete titration used to correct acidosis?

Answer 34

A new bicarbonate ion is added to the extracelular fluid.

Question 35

How is incomplete titration used to correct metabolic alkalosis?

Answer 35

bicarbonate ions are removed from extracelular fluid by renal excretion.

Question 36

What is the role of intercalated cells in hydrogen ion transport, and where are these cells found?

Answer 36

They use primary active transport to secrete hydrogn ions into the lumen. They are found in the late distal renal tubules.

Question 37

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

Answer 37

4.5

Question 38

Wha is the 2-step process of hydrogen ion secretion in intercalated cells?

Answer 38

Dissolved carbon dioxide in intercalated cells combines with water to form carbonic acid. The carbonic acid dissociates into bicarbonate, which is rapidly reabsorbed into the blood, and hydrogen ion, which is secreted ino the tubular lumen via hydrogen-ATPase transporters.

Question 39

How are excess hydrogen ions generated?

Answer 39

They are produced from nonvolatile acids. They are removed via renal excretion.

Question 40

What limits the amount of free hydrogen ion that can be excreted?

Answer 40

The minimal urine pH, which is about 4.5.

Question 41

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

Answer 41

Phosphate buffer system Ammonia buffer system

Question 42

How does the excretion of excess hydrogen ions lead to the formation of new bicarbonate ions?

Answer 42

Hydrogen ions combine with other buffers in the tubular lumen. This allows excess bicarbonate ion to be created.

Question 43

How does the renal system handle excess base?

Answer 43

The kidneys will not reabsorb all the filtered bicarbonate ion. This is the same as adding hydrogen ion to the extracellular fluid, and the pH of the extracellular fluid returns to normal.

Question 44

How can the respiratory system produce acidosis?

Answer 44

Acidosis occurs when the ratio of bicarbonate ion to carbon dioxide in extracellular fluid decreases. A decrease in bicarbonate ion occurs during metabolic acidosis, and an increase in carbon dioxide occurs in respiratory acidosis.

Question 45

How can the respiratory system produce alkalosis?

Answer 45

Alkalosis occurs when there is an increase in the rate of bicarbonate to hydrogen ion concentration. It is corrected by excreting excess bicarbonate in the urine. This adds hydrogen ions to extracellular fluid.

Question 46

What is the primary compensatory response of respiratory acidosis?

Answer 46

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

Question 47

What is the primary compensatory response of metabolic acidosis?

Answer 47

Increased ventilation rate new bicarbonate is added to the extracellular fluid.

Question 48

How does the respiratory system compensate for decreased carbon dioxide concentration?

Answer 48

There is a reduction in plasma bicarbonate ion concentration caused by renal excretion of bicarbonate ion.

Question 49

How does the respiratory system comopensate when there is metabolic alkalosis?

Answer 49

There is decreased ventilation and increased renal bicarbonate ion excretion.

Question 50

What is an acid?

Answer 50

A compound that releases hydrogen ions.