Acid Base Balance Flashcards
What are the systems the body uses for buffering? How long do they take?
in the blood immediately, respiratory system minutes to hours, kidney takes hours to days
What is the Henderson-Hasselbalch equation for pH balance in the body?
pH= pK + log [HCO3] / a[PCO2] or pK+ kidney/lung; a is the solubility constant (amount of CO2 that can be dissolved; as long as ratio is 20 or about 20, pH will be normal or near normal
What enzyme catalyzes CO2 and water buffering it?
carbonic anhydrase, it becomes H2CO3 which falls apart to bicarbonate and hydrogen
How does the kidney handle H+?
Co2 in the cell or diffused in from the lumen or the blood, combines with cellular H2O to form H2CO3 accelerated by carbonic anhydrase, H2CO3 rapidly breaks down in the cell as H and HCO3
How does H move across the luminal membrane?
intracellularly produced hydrogen ions are active pumped into tubular fluid this raises hydrogen concentration and lower pH, in PT 6.9, DT and CT pH 6.5, CD pH can be lowered to 4.5
How does the movement of H relate to Na in the kidney?
one sodium moves into the cell for every hydrogen which is secreted from the cell; mechanism is sometimes termed Na/H antiporter
What reaction happens btwn hydrogen and bicarbonate in tubular fluid?
pumped out hydrogen reacts with the filtered bicarbonate to make carbonic acid which disassociates into H2O and CO2, CO 2 diffuses into cell depending on partial pressures
How does H2CO3 move across the renal interstitium?
bicarbonate generated inside tubular cell diffuses across basolateral membrane into the interstitial fluid for every hydrogen secreted into the tubular fluid there is a bicarbonate reabsorbed roughly
How does bicarbonate move in relation to H in the kidney?
slight excess of H secretion over HCO3 filters, all of HCO3 filtered is reabsorbed, 90% in PT and remaining 10 in DT; vegetarians however do not produce excess hydrogen and would not reabsorb all the bicarb
During alkalosis what changes in the kidney?
H+ can’t reabsorb all the HCO3, it is excreted and Urine pH is as high as 8.0
During acidosis what changes in the kidney?
increase in H+, more is secreted until pH 4.5 reached then can’t pump out anymore, NH3 and HPO4 remove H+, NH4 can handle most increases in H, maximum secretion capacity occurs over days
How does the kidney compensate for metabolic acidosis?
bicarb deficiency- diarrhea, ketoacidosis, acid ingestion; increased renal secretion of H, renal generation of new bicarb
How does the kidney compensate for metabolic alkalosis?
HCO3 excess- vomiting loss of H; increase HCO3 excretion and decreased renal secretion of H
How does the kidney compensate for respiratory acidosis?
CO2 excess- hypoventilation, HF, pulm. edema; increased secretion of H increased renal generation of HCO3
How does the kidney compensate for respiratory alkalosis?
CO2 deficiency- hyperventilation, decreased [O2] atm; decreased renal secretion of H and dump bicarb in urine, increased HCO3 excretion
how does Cl move in relation to bicarb in the kidney and ECF?
the chief anions in ECF, appears to be fixed total anionic content if one decreases the other increases; so if [Cl] decreases due to vomiting then [bicarb] increases causing hypochloremic alakalosis
What effect does aldosterone have on hydrogen?
changes in aldosterone change H by changing potassium
What are the three types of acids and examples that occur in the body?
volatile- CO2 (production from regulation), fixed acids- H2SO4 from sulfer containing amino acids and H3PO4 many sources from the diet and organic acids- lactic acid and acetoacetic acid from metabolism of carbs and fat, anaerobic metabolism, lactic acid prod. often occurs in hemorrhagic shock, acetoacetic acid which is often increased in diabetes
What is the first line of defense in the body against acid?
buffers- alkalai salt/weak acid (NaHCO3/H2CO3); there is a cellular component and a plasma component
