Lecture 9: Renal & Respiratory Compensation Flashcards
how does metabolic alkalosis affect pH and [HCO3-]
increases pH
increases [HCO3-]
how does metabolic acidosis affect pH and [HCO3-]
decreases pH
decreases [HCO3-]
what is the effect of compensation in response to metabolic alkalosis
increases PCO2
what is the effect of compensation in response to metabolic acidosis
decreases PCO2
what is the effect of respiratory alkalosis on pH and PCO2
pH increases
PCO2 decreases
what is the effect of respiratory acidosis on pH and PCO2
pH decreases
PCO2 increases
what is the effect of compensation in response to respiratory alkalosis
decreases [HCO3-]
what is the effect of compensation in response to respiratory acidosis
increases [HCO3-]
what 3 mechanisms help keep plasma pH within a narrow range
- buffers
- respiratory response
- renal response
when blood gases and or pH change, _________ trigger changes in ventilation (tidal volume and breathing rate)
chemoreceptors
what do brainstem receptors monitor
CO2 and pH
what do peripheral receptors monitor
O2, CO2, pH
Carotid and aortic bodies monitor ??
O2, CO2, pH
b/c they are peripheral chemoreceptors
how do glomus cells respond when O2 tension or pH decreases, or when CO2 increases
depolarize
a decrease in PaO2 below ____-_____mmHg causes carotid and aortic bodies to stimulate respiration
60-70
central chemoreceptors monitor _____
CO2 (and pH)
how does CO2 effect breathing
CO2 crosses BBB
increases H+ ion concentration in brain interstitial fluid, activating central chemoreceptors
what happens to breathing rate if pH decreases in CSF
breathing increases
what happens to breathing rate if pH increases in CSF
breathing rate decreases
how doe the kidneys excrete an acid load?
- bicarbonate reabsorption
- titratable acidity
- ammonia genesis and NH4+ excretion
- bicarbonate secretion if available in excess
where in the tubular system is H+ secreted
proximal tubule
is bicarbonate freely filtered?
yes
bicarbonate uptake is dependent on the activity of _______ in the cell ?
carbonic anhydrase
within the cell, ______ facilitates the generation of H+ and HCO3-
CA-II
what is the most important transporter in the PT
Na/H+
what facilitates the production of water and CO2 from luminal carbonic acid
membrane bound carbonic anhydrase
how does HCO3- exit the cell
by crossing the basolateral membrane
what are the steps of bicarbonate reabsorption
- w/in the cell, CA-II facilitates the generation of H+ and HCO3-
- H+ is secreted into tubular fluid
- membrane-bound CA facilitates production of water and CO2 from luminal carbonic acid
- membrane permeable for CO2
5.HCO3- exits cell across basolateral membrane
what are the 3 transporters in the apical membrane of epithelial cells that secrete protons
- Na+/H+ exchanger
- H+ATPase
- K+/H+ ATPase
where in the tubular system is HCO3- reabsorbed
Collecting Duct
what is titratable acidity
- kidney excretes H+ w/ urinary buffers like phosphate and urate
- secreted protons bound to buffer ions are retained in tubule fluid then excreted - a “new HCO3-“ is generated
how does ammoniagenesis and NH4+ excretion occur
- kidney metabolizes glutamine
- NH4+ is excreted or returned to blood
- HCO3- is returned to the blood as “new HCO3-“
3 steps of ammonium excretion
- PT: ammoniagenesis enables bicarbonate production and absorption; NH4+ is transported into tubule fluid
- TAL: NH4+ is reabsorbed by Na/K/2Cl co-transporter (medullary recycling)
- CD: ammonia trapping
- High NH3/NH4+ concentrations in medullary interstitium favors excretion
renal removal of NH4+ is enhanced by ________ in dogs, chickens, rats and mice but not in cats or rabbits
acidosis
how do the kidneys excrete a load of [H+] or replace a bicarbonate deficit?
- reabsorption of all filtered bicarbonate
- additional H+ secreted via H+ATPases attached to bases (either titratable acids or via glutamine metabolism)
in the cortical CD, what type of cells contain H+ATPase in the basolateral plasma membrane
type B intercalated cells
type B intercalated cells are rich in ______ ?
cytoplasmic carbonic anhydrase
what exchanger is in the apical plasma membrane of the CD and mediates HCO3- secretion
Cl-/HCO3-, pendrin
what is the pendrin transporter (Cl/HCO3-) dependent on
sufficient Cl levels
- low Cl levels can cause impairment of bicarbonate secretion by type B intercalated cells —–> metabolic alkalosis
Renal response to Alkalosis results in a reduction of ______ excretion and an increase in _______ secretion
reduced acid (NH4+) excretion
increased bicarbonate secretion
renal response to Acidosis results in the reduction/elimination of all _______ from urine and promotes ______ secretion
elimination of HCO3- from urine
acid secretion
