Acid-Base Regulation Flashcards
(45 cards)
What is the normal pH of the ECF?
7.4
Which reactants form volatile (CO2-derived) H+/HCO3- and where are these products eliminated?
Aerobic Glucose metabolism
Aerobic Fat Metabolism
Eliminated in the lungs
Which reactants form fixed (non-CO2-derived) H+ and where is the acid eliminated?
Anaerobic Glucose metabolism (forms H+ and Lactic acid)
Aerobic Cystein metabolism (produces H+ and Sulfate)
Aerobic Phosphoprotein metabolism (produces H+ and Phosphate)
Eliminated in the Kidney
What is the normal pH range for ICF?
6.0 - 7.4
What is the normal pH range for Urine?
4.5 - 8.0
What is normal pH of gastric HCl?
0.8
What are the four buffer systems?
Bicarbonate
Hemoglobin
Phosphate
Plasma Proteins
What is the pK value of the bicarbonate buffer system and what does it mean?
The pK value of te bicarbonate buffer system is 6.1. This means at a pH of 6.1, the amounts of HCO3- and H2CO3 are equal
What role does the lungs have on pH regulation?
Regulates retention of CO2, therefore controlling the presence of H2CO3 (carbonic acid)
Rate: minutes-hours
What is the role of Ionic shifts in pH regulation?
Controls the exchange of Na+ and K+ for H+
Rate: 2-4 hours
What is the role of the kidneys in pH regulation?
Bicarbonate reabsorption and regeneration, ammonia formation, phosphate buffering
Rate: hours to days
What is the role of Bone in pH regulation?
Exchanges calcium and phosphate, and release of carbonate
How does ionic shifts buffer in response to Acidemia
Acidemia is acidic blood (<7.35)
H+ are exchanged for K+, causes ICF to take in more H+
How does ionic shifts buffer in response to Alkalemia
Alkalemia is alkaline blood (>7.45)
K+ is exchanged for H+, causing ICF to take in more K+ in exchange for H+
What is the henderson hasselbach equation?
pH = pka + log ([Base]/[Acid])
What should you know when applying the henderson hasselbach equation to the Bicarbonate buffer system?
pH = pka + log ([Base]/[Acid])
pH = 6.1 + log ([HCO3-]/[H2CO3])
Note that the HCO3- concentration is regulated by the kidneys and the the H2CO3 concentration is regulated by the lungs
H2CO3 concentration = 0.03 * Pco2 {plasma CO2 concentration}
If the Base/Acid ratio is equal to 20, then the pH will equal 7.4
What happens to pH when you hold your breath? What happens when you breath quickly?
Hold breath -> Acidosis
Breath quickly -> Alkalosis
What segments are involved in Bicarbonate reabsorption?
Proximal Tubule (85%)
Thick Ascending limb of The Loop of Henle (10%)
Collecting Duct (4.9%)
Describe how Bicarbonate is reabsorbed in the Proximal Tubule (include the channels involved)
Na/H Exchanger and H-ATPase bring H+ into the lumen
Filtered HCO3- binds with the H+ to form H2CO3
H2CO3 is converted to CO2 and H2O via Carbonic Anyhydrase on apical membrane
CO2 and Water diffuse into the tubule cell where intracellular carbonic anhydrase converts CO2 and H2O into H2CO3
H2CO3 splits into HCO3- and H+
HCO3- Leaves the cell via a Na-HCO3 Symporter (which carries 3 HCO3 and 1 Na+ into the interstitium) or a HCO3-Cl exchanger (which sends HCO3- to the interstitium and sends Cl- into the cell)
What factors directly increase H+ secretion as a result of Acid/Base regulation?
Decreased serum HCO3-
Increased Serum CO2 levels
What factors directly decrease H+ secretion as a result of Acid/Base regulation?
Increased serum HCO3-
Decreased serum CO2 levels
How does hypokalemia affect H+ secretion?
Hypokalemia increases H+ secretion
K+ reabsorption occurs as H+ secretion occurs
How does hyperkalemia affect H+ secretion?
Hyperkalemia decreases H+ secretion
K+ reabsorption parallels H+ secretion.
Hyperkalemia reduces K+ reabsorption, thus H+ secretion decreases
How does a decrease in ECF volume affect H+ secretion?
Decreased ECF volume increases H+ secretion
