Acid-Base Regulation

Question 1

primary lines of defense against changes in H+ concentration in the body fluids:

Answer 1

The chemical acid-base buffer systems of the body f luids,
The respiratory system,
The kidneys,

Question 2

This mechanism operates minutes and acts as a second line of defense

Answer 2

respiratory system

Question 3

This mechanism operates slowly but powerfully over a period of hours or several days to regulate the acid-base balance

Answer 3

The kidneys

Question 4

not a major buffer in the extracellular f luid but is important as an intracellular buffer and as a buffer in renal tubular fluid.

Answer 4

phosphate buffer system

Question 5

The most important extracellular fluid buffer is

Answer 5

bicarbonate buffer system

Question 6

Rise in blood bicarbonate is compensated by

Answer 6

Renal excretion of bicarbonate

Question 7

Gives the Relation of Bicarbonate and Carbon Dioxide to pH.

Answer 7

Henderson-Hasselbalch Equation

Question 8

When disturbances of acid-base balance result from primary changes in extracellular HCO3−, they are referred to as

Answer 8

metabolic acid-base disorders

Question 9

Acidosis caused by an increase in Pco2 is called

Answer 9

respiratory acidosis,

Question 10

Because the lungs expel CO2 from the body, rapid ventilation by the lungs decreases the concentration of CO2 in the blood, which in turn increases the H2CO3 and H+ concentrations in the blood.
True or False

Answer 10

False. which in turn decreases the H2CO3 and H+ concentrations in the blood.

Question 11

a decrease in pulmonary ventilation results to

Answer 11

increases CO2 and H+ concentrations in the blood.

Question 12

Increased Hydrogen Ion Concentration Stimulates

Answer 12

Pulmonary Ventilation.

Question 13

overventilation (rare) causes a reduction in Pco2 and a tendency toward

Answer 13

respiratory alkalosis.

Question 14

A large quantity of ________is filtered continuously into the tubules

A large quantity of ________ is also secreted into the tubular lumen,

Answer 14

HCO3−

H+

Question 15

If more H+ is secreted than HCO3− is filtered, there is a net gain of acid from the extracellular fluid.
True or False

Answer 15

False. Loss

Question 16

The kidneys regulate extracellular fluid H+ concentration through three basic mechanisms: (

Answer 16

1) secretion of H+, (
2) reabsorption of f iltered HCO3−, and (
3) production of new HCO3

Question 17

Hydrogen ion secretion and HCO3− reabsorption occur in virtually all parts of the tubules except t

Answer 17

descending and ascending thin limbs of the loop of Henle.

Question 18

Bicarbonate is not reabsorbed directly by the tubules; instead, it is reabsorbed as a result of the reaction of

Answer 18

secreted H+ with filtered HCO3− in the tubular fluid under the influence of carbonic anhydrase in the tubular epithelium.

Question 19

H+ Is Secreted Into the Tubular Fluid by

Answer 19

Sodium-Hydrogen Countertransport

Question 20

which is reabsorbed across the basolateral membranes of the tubules.

Answer 20

HCO3−

CO2 diffuses into the cell and is used to re-form H2CO3 and eventually HCO3−

Question 21

Normally, more than 99 percent of the filtered HCO3− is reabsorbed by the renal tubules, with about 95 percent of the reabsorption occurring in the

Answer 21

proximal tubules, loops of Henle, and early distal tubules.

Question 22

capable of increasing the H+ concentration as much as 900-fold,

Answer 22

late distal tubules and collecting ducts

Question 23

lower limit of pH that can be achieved in normal kidneys.

Answer 23

4.5

Question 24

Under normal conditions, the rate of tubular H+ secretion is about________ and the rate of filtration of HCO3− is about__________.

Answer 24

4400 mEq/day,

4320 mEq/day

Question 25

Most of the H+ is not excreted as free H+ but, rather, in combination with

Answer 25

other urinary buffers, especially phosphate and ammonia (

Question 26

Most Important Urinary Buffer in Chronic Acidosis

Answer 26

Ammonia

Question 27

Ammonia ion is synthesized from glutamine, which is actively transported into the cells of

Answer 27

proximal tubules, thick ascending limbs in the loop of Henle, and distal tubules

Question 28

One of the most important features of the renal NH3 buffer system is that

increasing the formation of NH4+ and new HCO3− to be used for H+ buffering.

Answer 28

renal glutamine metabolism is markedly stimulated by acidosis,