Renal 5: Acid-Base Balance Flashcards
body fluid pH is tightly regulated by ___
buffering
___ is the most important physiological pH buffer
bicarbonate
bicarbonate buffering is regulated by the ___ and ___
kidneys and lungs
what happens to practically all of the HCO3 filtered by the kidneys?
reabsorbed by different mechanisms
secreted H is excreted as __ or ___
titratable acid or as NH4+
acid-base disorders have several causes and result in renal and respiratory ___ mechanisms
compensatory
the kidneys respond to changes in blood pH by ___ and ___
inceasing or decreasing acid secretion and HCo3 reabsorption
what is the pH range of urine?
4.5-8
what are the 2 acid inputs to plasma?
diet (fatty and amino acids) and metabolism (CO2, H2O, Lactic acids, ketoacids)
what are the 2 acid outputs from the plasma?
expiration of volatile acids from the lungs & excretion of fixed acids by the kidneys
the phosphate buffers are important in __ and ))
intracellular fluid and urine
what enzyme changes co2 and water into carbonic acid?
carbonic anhydrase
carbonic acid dissociates into __ and __
bicarbonate and H+
buffers prevent ___ in pH when H+ levels change
large changes
at low pH, what is the dominant form?
weak acid (protonated)
at high pH what is the dominant form?
weak base, (deprotonated)
the ___ equation relates the buffer levels to overall pH
henderson hasslebach
at low pH is CO2 or Bicarb dominant?
CO2
at high pH is CO2 or Bicarb dominant?
Bicarb
what happens to CO2 and hCO3- when acid is added? 1
HCO3 is reabs and CO2 expired
what happens to CO2 and HCO3- when base is added?
HCo3 excreted and Co2 decreased reabsorption
at pH 7.4, what is the dominant form of the bicarbonate buffer?
HCO3-
most of the HCO3 is reabsorbed in ____ of the nephron
proximal tubule
secretion of H is done by ___ transporters in the __ membrane of the proximal tubule
Na/H antiporter; apical
the secretion of H is driven by the formation of ___ in the cell in the proximal tubule
H2CO3
bicarbonate is reabsorbed across the __ membrane by ___ in the proximal tube
basolateral; facillitated diffsuin transporte
the H ions that secreted are used to reclaim HCO3 to make ___ and __
co2 and water
the conversion of H2CO3 to h20 and Co2 is performed by ___ which is tethered to the apical membrane
carbonic anhydrase
the Co2 made when H is secreted is used to make more __ within the cell
carbonic acid (that will make bicarb and more H for more cycling)
net secretion of H; charge of tubular fluid pH__ in the proximal tube
none; none
how is H secreted across the apical membrane in the collecting duct?
proton pump (H ATPase)
how is bicarb reabsorbed across the baso membrane in the collecting duct?
HCO3 Cl transporter
in the collecting duct, the secretion of H is coupled to __
formation and reabsorption of HCo3
Alpha intercalted cells act reverse to__
acidosis
beta intercalated cells act to reverse __
alkalosis
___ is secreted and __ is reabsorbed by the alpha intercalated cells
H; HCO3
___ is secreted and ___ is reabsorbed by the beta intercalated cells
hco3; H
what transporter is used to secrete HCO3 from the beta intercalated cells?
pendrin
t/f pendrin is special to the apical membrane
t
is the alpha or beta intercalated cell dominant under most cases?
alpha
in diabetic patients, the the total production of H and excretion as either titratable acids or NH4 is much ___ compared to normal
higher
how does the total production of H and excretion as Nh4 and titratable acids in patients with renal failure compare to that of a normal patient?
total H is the same; but excretion in these forms is lower
metabolic acidosis is caused by __
decresed HCO3
metabolic alkalosis is caused by __
increased HCO3
respiratory acidosis is caused by
increased PCO2
respiratory alkalosis is caused by
decreased PCO2
give 2 possible conditions leading to metabolic acidosis
diarrhea (loss of hCO3) and ketoacidosis (raised H)
give 2 possible conditions leading to metabolic alkalosis
vomiting (loss of H) and eating too much HCO3
give an example of a condition that may cause respiratory acidosis
COPD / hypoventillation
give an example of a condition that may cause respiratory alkalosis
hyperventillation
what is the respiratory compensation for metaboilc alkalosis?
hypoventilation
what is the respiratory compensation for metabolic acidosis?
hyperventilation
in response to acidosis, phosphate reabsorption is ___ by the proximal tubule
decreased (to maintain buffering in urine)
in response to alkalosis, phosphate reabsorption id ___ by the proximal tubule
icreased
pH above 7.4 is
alkalosis
pH below 7.4 is
acidosis
{HCO3} above 24 mEq/L is
metabolic alkalosis
[HCO3] below 24 mEq/L is
metabolic acidosis
PCO2 below 40 mmhg is
respiratory alkalosis
PCO2 above 40 mmHG is __-
respiratory acidosis
