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
what is URINARY BUFFERING
the process where secreted H+ are BUFFERED IN the URINE by COMBINING with weak acids or with NH3 AMMONIA to be excreted
what is the major ADAPTATION to an INCREASED ACID LOAD
INCREASED AMMONIUM SECRETION (NH4+)
ammonium production also has a role in
further generation of bicarbonate ions
how is H+ REMOVED from BLOOD
by a…
SODIUM-HYROGEN EXCHANGER
(sodium into blood and H+ into cell)
(another exchanger for H+ into filtrate)
how is NH4+ (Ammonium) REMOVED from DCT CELLS
SODIUM-AMINE EXCHANGER
NH4+ removal means a LOT of H+ REMOVED
what is AMINO ACID DEAMINATION in DCT
BREAK DOWN of PROTEINS FROM DIET into AMINO ACIDS
- LIBERATES HCO3- and H+ IONS
- BUFFERED by NH3
into NH4+
Diets rich in MEATS provide … to the bloods when digested
ACIDS
Diets rich in FRUITS and VEGETABLES are rich in…
BICARBONATES
exercising muscles produce..
lactic acid
(must be eliminated from body or metabolised)
Respiration variations in gaseous exchange can affect our blood..
pH
what are H+ BUFFERED WITH in urine
NH3 (AMMONIA)
- to form NH4+ (AMMONIUM)
