54 Acid base homeostasis

Question 1

This portion of the nephron secretes H+ and reabsorbs bicarbonate?

Answer 1

The proximal tubule

Question 2

T/F. 60 % of filtered bicarbonate reabsorbed in the PT. The rest is reabsorbed in the ascending loop of henle or the collecting duct

Answer 2

False. ~85% is reabsorbed in the PT. The rest is reabsorbed in the ascending loop of henle or the collecting duct.

Note: The amount that is reabsorbed varies depending on whether acidosis or alkalosis is occurring

Question 3

T/F. For each bicarbonate that is reabsorbed in the PT, one H+ is secreted. However, the H+ does not contribute to the pH of the urine

Answer 3

True

Question 4

What are the locations of carbonic anhydrase in the kidneys?

Answer 4

In the tubular cells and on the membrane brush border

Question 5

T/F. In the presence of a Carbonic anhydrase inhibitor, you cannot reabsorb bicarbonate, leading to increased excretion (pH of blood will decrease)

Answer 5

True

Question 6

T/F. After all bicarbonate has been reabsorbed, the remaining H+ in the lumen will contribute to the pH of the filtrate.

Answer 6

True

Question 7

H+ is secreted into the lumen. This H+ then combines w/ a phosphate buffer and is excreted as a titratable acid (w/ phosphate buffer)

Answer 7

Titratable acid (method of managing urine pH)

Question 8

This is the major adaptation to acidosis (acid load). Acidosis promotes enzymatic glutamine breakdown into bicarbonate and ammonia. Bicarbonate reabsorption helps control acidosis. Ammonia is transported into the lumen (antiporter), where it acts as a base and helps manage the pH

Answer 8

Ammonia (method of managing urine pH)

Question 9

T/F. The kidney synthesizes glutamate. It then activates enzymatic breakdown of glutamate, which is degraded into bicarbonate and ammonia. The ammonia is transported into the tubular lumen where it neutralizes the pH of the urine

Answer 9

False. The kidney synthesizes glutamine. It then activates enzymatic breakdown of glutamine, which is degraded into bicarbonate and ammonia. The ammonia is transported into the tubular lumen where it neutralizes the pH of the urine

Question 10

These cells reabsorb Na+ and secrete K+

Answer 10

Principal cells

Question 11

These cells control H+ and HCO3- secretion or reabsorption

Answer 11

Intercalated cells

Question 12

These cells secrete H+ ions into the tubular lumen. Occurs by V-ATPase H+ secretion and K+/H+ antiporter (both are active transport). H+ is provided by the carbonic anhydrase reaction. Bicarbonate created in this process is reabsorbed and contributes to the stabilization of blood pH

Answer 12

Alpha-intercalated cells

Question 13

These cells secrete bicarbonate in the DT and collecting ducts

Answer 13

Beta-intercalated cells

Question 14

Which type of intercalated cells are increased during acidosis?

Answer 14

Alpha. B/c this transports H+ into the filtrate while reabsorbing bicarbonate that can contribute to pH neutralization

Question 15

Which type of intercalated cells are increased during alkalosis?

Answer 15

Beta. B/c these cells increase excretion of bicarbonate

Question 16

T/F. The RAAS also influences the H+ concentration. Ang II promotes Na+ reabsorption in the PT. It does this by promoting the Na+/H+ antiporter expression.

Answer 16

True

Question 17

This hormone promotes H+ ion secretion by promoting H+/K+ antiporter (bicarbonate is then reabsorbed).

Answer 17

Aldosterone

Question 18

Excessive stimulation of the RAAS is associated w/ ___

Answer 18

Alkalosis

Question 19

What is the normal blood pH?

Answer 19

7.4

Question 20

Normal bicarbonate concentrations are ___

Normal CO2 levels are ___

Answer 20

bicarbonate: 24 mEq/L

CO2: 40 mmHg

Question 21

T/F. The kidney is able to regulate bicarbonate and H+ by: reabsorbing and generating bicarbonate and secreting H+

Answer 21

True

Question 22

A primary disturbance that has its origins in CO2 mismanagement

Answer 22

Respiratory disturbance

Question 23

A primary disturbance that has its origins in bicarbonate (or metabolic ion) mismanagement

Answer 23

Metabolic disturbance

Question 24

Increase H+ secretion, increase bicarbonate reabsorption, and produce new bicarbonate (a product of increased H+ secretion)

Answer 24

Renal compensation for acidosis

Question 25

decrease H+ secretion, decrease bicarbonate reabsorption, increased excretion of bicarbonate in urine (increase filter load past the reabsorptive capacity)

Answer 25

Renal compensation for alkalosis

Question 26

T/F. Alkalosis usually presents w/ hyperkalemia

Answer 26

False. Alkalosis usually presents w/ hypokalemia (low ICF potassium levels)

Question 27

T/F. Acidosis usually presents w/ hyperkalemia

Answer 27

True

Question 28

This hormone stimulates the Na+/H+ exchanger. This increases the capacity of the kidney to reabsorb bicarbonate (H+ combines with bicarbonate in the tubular lumen, which is then converted into water and CO2 by carbonic anhydrase… CO2 then diffuses into the tubule cells, which convert it back into bicarbonate and reabsorb it)

Answer 28

Angiotensin II

Question 29

The difference b/t measurable and non-measurable cations in the blood. Na+, Cl-, and bicarbonate are the only measure anions/cations of the blood

Answer 29

Anion gap

Question 30

Occurs when Cl levels have increased to compensate for the low bicarbonate levels. This presents as a normal anion gap in a patient that is known to have metabolic acidosis

Answer 30

Hyperchloremic metabolic acidosis

Question 31

Occurs when the unmeasured anions are increased. Caused by lactic acidosis, ketoacidosis, and alcoholism

Answer 31

Increased anion gap (normochloremic)

Question 32

What is the primary adaptive response of the kidney to sustained acidosis?

Answer 32

Ammoniagenesis (production of ammonia, which can buffer the excreted H+)

Question 33

Optimal recovery from a severe metabolic acidosis (or alkalosis) is most dependent on what?

Answer 33

The rate of H+ renal excretion