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25 Cards in this Set

  • Front
  • Back
What three body systems maintain the acid-base homeostasis?
Intracellular and Extracellular buffers.

Lungs

Kidneys
IC and EC buffers and lungs are responsible for ____ pH changes whereas the kidneys are responsible for _____ changes.
IC/EC/lungs: rapid pH changes.

Kidneys: long-term changes.
What are some IC and EC buffers?
Hemoglobin

Carbonates

Phosphates

HCO3
What do kidneys secrete the majority of for acid-base balance?
H+
True or False:

Nonvolatile acids produced during metabolism do not circulate as free acids, but are immediately buffered.
True!
Where are nonvolatile acids used in buffering excreted?
In the kidneys.
In order to maintain acid-base balance, the kidney must excrete ____ salts and replenish lost ____.
Excrete Na+ salts and replenish lost HCO3-.
How is the reabsorption of filtered HCO3- and excretion of acid accomplished?
Through H+ secretion by the nephrons.

PT secretes the bulk of the acid, and CD controls net acid excretion and final urine pH.
What must net acid excretion equal?
Nonvolatile acid production.
What three transporters provide the majority of acid excretion in the renal tubules?
Na+/H+ antiporter. (PT)

H+ ATPase (CD)

H+/K+ ATPase (CD)

PT=Proximal Tubule
CD=Collecting Duct
What are the three most important buffers in the tubular fluid that accept secreted H+?
HCO3- (Predominates because of its high concentration)

Ammonia

Phosphate
How is NH3 produced in the kidneys?
Via hydrolysis of the amino acid glutamine.

Glutamine --> NH4+ + HCO3-
How does Plasma K+ concentrations alter NH4+ production?
Hyperkalemia inhibits NH4+ production and hypokalemia stimulates production.
Why is Ammonia an important urinary buffer?
It is produced by the kidney and its synthesis and excretion can be regulated in response to the acid-base requirements of the body.
The proximal tubule has a high capacity for ___ secretion and ___ resorption.
H+ secretion

HCO3- resorption.
How much of filtered HCO3- is reabsorbed by the Proximal Tubule
80-90%
True or False:

Since the PT has a high capacity for H+ secretion and HCO3- reabsorption it is able to maintain a large pH gradient across the apical plasma membrane.
False.

It can't maintain a large pH gradient, so the pH of tubular fluid as it leaves the proximal tubule will be similar to that of the glomerular filtrate.
What part of the nephron determines the final urine pH?
The collecting ducts.
What is the normal range of urine pH in carnivores? In Ruminants?
Carnivores: 5.5-7.7

Ruminants: 6-9
How does the collecting duct generate an acidic urine?
By secreting protons.
What does the rate of H+ secretion depend on?
The number of proton pumps in the apical plasma membrane.
What are some primary factors that regulate H+ secretion in the nephron?
INC H+ secretion.
Decreased plasma HCO3- concentration.

Increase in partial pressure of arterial carbon dioxide

DEC H+ secretion
Increase in plasma HCO3- concentration

Decrease in partial pressure of arterial carbon dioxide.
What are some secoondary factors that regulate H+ secretion in the nephron?
INC H+ secretion

Increase in filtered load of HCO3-
Decrease in ECF volume
Increase in An II
Increase in ADS
Hypokalemia

Decreased H+ secretion

Decrease in Filtered load of HCO3-
Increase ECF volume
Decrease in ADS
Hyperkalemia
___ is thought to increase the number of proton transporters in the apical plasma membrane. It increases the reabsorption of NA+ and increases the secretion of H+ and K+
ADS (Aldosterone)
What cells in the Collecting Duct are responsible for HCO3- secretion?
Type B intercalated cells.

(They do the reverse of the acid secreting cells)