8.3 Renal Physiology II - Fluid Balance ACID-BASE Flashcards
In HUMANS, pH of Extracellular fluid must remain between..
7.35 - 7.45
below 7.35: acidosis
above 7.45: alkalosis
fluctuation can result in coma, cardiac failure and circulatory collapse
pH is from a Mixture of..
H+ IONS and SODIUM BICARBONATE (BUFFER)
need constant ratio to maintain correct pH
how do we get H+ and HCO3- in BLOOD
CO2 and H20 (products of respiration) COMBINE to form CARBONIC ANHYDRASE
- not stable
BREAKS DOWN into H+ and HCO3-
in order to MAINTAIN ACID-BASE BALANCE what 2 tasks must the KIDNEY do
- REABSORB FILTERED BICARBONATE (buffer)
- EXCRETE DAILY ACID LOAD (H+)
how does the KIDNEY achieve EXCRETION of DAILY ACID LOAD (3)
by:
- HCO3- REABSORPTION
- SECRETING H+
- SECRETING AMMONIUM (NH4+)
Where in the nephron is MOST of the HCO3- RECLAIMED and by what synthesis
PCT
by DE NOVO SYNTHESIS (new bicarbonate molecules created)
in a healthy nephron, how much of the BICARBONATE HCO3- is RECLAIMED in PCT (DE NOVO SYNTHESIS)
85-90%
explain how HCO3- is REABSORBED FROM PCT into blood (high HCO3- after bowman’s capsule)
- in TUBULAR LUMEN (FILTRATE) HCO3- not stable and BROKEN DOWN into carbonic acid (H2CO3) to CO2 and H20
- CO2 DIFFUSES INTO PCT CELLS
- CO2 and H20 in PCT CELLS RECOMBINE (using carbonic anhydrase) to form H2CO3 which dissociates to HCO3- and H+ (BICARBONATE REASSEMBLED)
- HCO3- TRANSPORTED OUT of CELLS with SODIUM NA+ into renal interstitial fluid into blood
- H+ Transported back INTO LUMEN (FILTRATE) by Na-H exchanger (H+ out of blood)
what can you find in the PCT cells that keep gradient steady for transport of molecules
NA-K ATPASE
LOTS of SODIUM
what happens to the H+ in the PCT CELLS and BLOOD
TRANSPORTED INTO FILTRATE
(using sodium)
where is there FURTHER RECLAMATION of BICARBONATE (HCO3-)
DCT and COLLECTING DUCT
how much HCO3- is RECLAIMED in the DCT and COLLECTING DUCT
10-15%
How is HCO3- RECLAIMED in DCT (and collecting duct)
- CO2- DIFFUSES INTO CELLS (from interstitial fluid)
- HCO3- ASSEMBLED
from CO2 + H20 using carbonic anhydrase to form H2CO2 - dissociates to HCO3- and H+ - HCO3- TRANSPORTED OUT
EXCHANGED for Cl- using HCO3- - CL- EXCHANGER - H+ TRANSPORTED INTO LUMEN (filtrate) WITH Cl- USING ATP
in DCT and collecting duct how does the HCO3- MOVE OUT of the DCT CELLS into BLOOD
EXCHANGED FOR CHLORIDE IONS
using bicarbonate-chloride EXCHANGER
in DCT and collecting duct how does the H+ MOVE INTO LUMEN (filtrate) from the DCT CELLS
TRANSPORTED WITH CHLORIDE Cl-
- uses ATP
