Lecture 19, acid bases Flashcards Preview

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Flashcards in Lecture 19, acid bases Deck (39):

Bicarbonate buffer system uses what acid/bases?

-use of carbonic annhydrase


Where can extra HCO3 be excreted from the body?



What is the net result of the combination of CO2 and H2O?

- increased levels of CO2 have the potential to decrease the pH of the blood.


What is the overall effect of lowering the CO2 blood concentration?

-decreased blood CO2 leads to decreased respiratory rate as there the blood pH will be more alkolitic.
-Therefore is [CO2] blood is decreased the CO2 blow-off will be decreased


The major function of the bicarbonate buffer system is what?

-control the levels of bicarb and [H]


What organs help control the bicarbonate buffer system?

-kidneys (bicarbonate concentration)
-lungs (control the pCO2)


Metabolic acidosis disorder is characteristic of what?

- decreased HCO3


Respiratory acidosis occurs how and where?

-from the lungs with increased levels of pCO2


Where does the phosphate buffer system have a major role?

-the renal tubular fluid and intracellular fluids


Why is the phosphate buffer system important in the kidney tubular fluids?

-higher concentration in the tubules
-the lower pH of the tubular fluids allows for a better operating environment for the buffer system


What is the overall net reaction result of the phosphate buffer system?

-strong acid is replaced by additional amounts of weak acid and a salt. Resulting in minimal pH change


What three ways can the kidneys regulate the extracellular H ion?

-reabsorb filtered bicarbonate ion
-secrete H ion
-produce new bicarbonate ions, that would be later reabsorbed


How is bicaronate reabsored into the renal insterstitial fluid and ultimately into the blood stream?

-NzHCO3 combines with H ion, to form H2CO3 and is broken down into CO2 and H2O
-CO2 and H2O is passively absorbed across the membrane, carbonic annhydrase converts the reactants into H2CO3 and breaks down into HCO3 and H ion.
-forming a cyclical pattern to absorb HCO3 and the H ion can move out of the cell via the Na-H exchanger to produce more carbonic acid in the tubular lumen


Where in the nephron does H ion secretion and HCO3 reabsorption occur?

-H ion secretion occurs as secondary active transport except in the descending/ascending thin limbs of henle loop
-active H ion begins in the late distal tubule in the intercalated cells
-80-90% of bicarbonate reabsorption occurs in proximal tubule


What process occurs in metabolic acidosis in the kidneys?

-regulation to correct the decreased pH, by reabsorbing bicarbonate and secreting new bicarbonate ion into the blood tissue.


What happens in metabolic alkalosis in the kidneys?

-bicarbonate ions are quickly removed from the extracellular fluid, via renal excretion


What is the 2-step process of H ion secretion by the intercalated cells?

-dissolved CO2 in intercalated cells combine with water and form carbonic acid
-carbonic acid dissociates into bicarbonate, becomes rapidly reabosorbed into blood, and H ion is secreted, by H-ATPase into tubular lumen.


What is the best way to describe the incomplete titration?

-There is not a one-to-one amount of ions being absorbed an secreted


What is the minimun amount of pH that the kidneys are able to achieve?



It is important to allow large amounts of H ion to be excreted, why?

the amount of nonvolatile acid from metabolism would lead to 2667 L of urine a day, if the H ion remained in free solution


How are excess H ions eliminated?

-as bicarbonate ion is formed the H ion is secreted into the lumen by Na-H antiporter.
- H ion binds with phosphate or ammonia to be excreted in urine
-bicarbonate ion is absorbed into the blood as a "new" ion


The phosphate buffer system does what?

Increases the pH of the blood.
-removes H ion from the blood to help form phosphate components, that produce NEW bicarbonate ion that can be secreted into the blood.
--loss of blood [H] and increase of blood [HCO3]


How can the kidneys correct for alkalosis?

-failure to reabsorb the filtered bicarbonate ion which will lead to decreased blood pH


What process occurs with increased levels of CO2?

-respiratory acidosis


What occurs with decreased levels of bicarbonate ions?

Metabolic acidosis


What is the primary compensating response for respiratory acidosis?

-Increase the plasma concentration of Bicarbonate, initially via the kidney.


Metabolic acidosis is compensated by what function?

-the lungs increase ventilation
- the kidneys can also begin to form new bicarbonate ion to extracellular


When does respiratory alkalosis occur? And what process begins to compensate for it?

-decrease in [CO2]
-caused by hyperventilation
--reduce plasma HCO3 by increased secretion into tubular lumen


Metabolic alkalosis occurs with what and is compensated how?

-increased plasma [HCO3]
--compensated by decreasing ventilation and increasing bicarbonate ion secretion into the tubular lumen


What are two buffer systems in the body, and what else can function as a buffer?

-proteins act as buffers


What buffer system is the most important buffering system in the renal tubular fluid?

-phosphate buffer system as it is closer to the optimal operating pH.


Compounds that dissociate incompletely into H ions and conjugate base are members of what compounds?

-Weak acids, incompletely dissociate
-Strong acids completely dissociate


The bicarbonate buffer system consists of a bicarbonate buffer salt and what other component?

-weak acid


Primary active H secretion uses H ATPase and occurs in what part of the renal tubules?

late distal tubules with intercalated cells


Most bicarbonate reabsorption occurs in what part of the renal tubule?

- proximal tubule


What occurs with a decrease in bicarbonate ion and results in the decrease in the ratio of bicarbonate ion to carbon dioxide in the extracellular fluid?

- Metabolic Acidosis
--as the bicarbonate ion level is being decreased


Respiratory alkalosis due to a decrease in CO2 caused by hyperventilation is compensated for by what mechanism?

- renal excretion of bicarbonate ion


What is the effect of Glutamine if it is absorbed into the tubular cells?

-glutamine degrades into 2 ammonium ion and 2 bicarbonate ion.
-new bicarbonate is reabsorbed
-ammonium secreted by Na anti porter
-ultimately buffers the H ion concentration


What does "new bicarbonate ion" refer to?

-production of excess bicarbonate in the tubular cells, as H ion is forced to combine with phosphate or ammonia in the lumen