Acid-Base Regulation Flashcards
primary lines of defense against changes in H+ concentration in the body fluids:
The chemical acid-base buffer systems of the body f luids,
The respiratory system,
The kidneys,
This mechanism operates minutes and acts as a second line of defense
respiratory system
This mechanism operates slowly but powerfully over a period of hours or several days to regulate the acid-base balance
The kidneys
not a major buffer in the extracellular f luid but is important as an intracellular buffer and as a buffer in renal tubular fluid.
phosphate buffer system
The most important extracellular fluid buffer is
bicarbonate buffer system
Rise in blood bicarbonate is compensated by
Renal excretion of bicarbonate
Gives the Relation of Bicarbonate and Carbon Dioxide to pH.
Henderson-Hasselbalch Equation
When disturbances of acid-base balance result from primary changes in extracellular HCO3−, they are referred to as
metabolic acid-base disorders
Acidosis caused by an increase in Pco2 is called
respiratory acidosis,
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
False. which in turn decreases the H2CO3 and H+ concentrations in the blood.
a decrease in pulmonary ventilation results to
increases CO2 and H+ concentrations in the blood.
Increased Hydrogen Ion Concentration Stimulates
Pulmonary Ventilation.
overventilation (rare) causes a reduction in Pco2 and a tendency toward
respiratory alkalosis.
A large quantity of ________is filtered continuously into the tubules
A large quantity of ________ is also secreted into the tubular lumen,
HCO3−
H+
If more H+ is secreted than HCO3− is filtered, there is a net gain of acid from the extracellular fluid.
True or False
False. Loss
The kidneys regulate extracellular fluid H+ concentration through three basic mechanisms: (
1) secretion of H+, (
2) reabsorption of f iltered HCO3−, and (
3) production of new HCO3
Hydrogen ion secretion and HCO3− reabsorption occur in virtually all parts of the tubules except t
descending and ascending thin limbs of the loop of Henle.
Bicarbonate is not reabsorbed directly by the tubules; instead, it is reabsorbed as a result of the reaction of
secreted H+ with filtered HCO3− in the tubular fluid under the influence of carbonic anhydrase in the tubular epithelium.
H+ Is Secreted Into the Tubular Fluid by
Sodium-Hydrogen Countertransport
which is reabsorbed across the basolateral membranes of the tubules.
HCO3−
CO2 diffuses into the cell and is used to re-form H2CO3 and eventually HCO3−
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
proximal tubules, loops of Henle, and early distal tubules.
capable of increasing the H+ concentration as much as 900-fold,
late distal tubules and collecting ducts
lower limit of pH that can be achieved in normal kidneys.
4.5
Under normal conditions, the rate of tubular H+ secretion is about________ and the rate of filtration of HCO3− is about__________.
4400 mEq/day,
4320 mEq/day
Most of the H+ is not excreted as free H+ but, rather, in combination with
other urinary buffers, especially phosphate and ammonia (
Most Important Urinary Buffer in Chronic Acidosis
Ammonia
Ammonia ion is synthesized from glutamine, which is actively transported into the cells of
proximal tubules, thick ascending limbs in the loop of Henle, and distal tubules
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.
renal glutamine metabolism is markedly stimulated by acidosis,
