L13-Acid base regulation Flashcards
What is the definition of ph in equation form?
pH=-log10[H+]
what is the HCO3- buffering equation in circulation?
H+ + HCO3- H2O + CO2
What are the normal arterial and venous values for pH?
- 4 arterial
7. 35 venous
What is the henderson hassleback equation for Hco3-?
pH = pK + log10([Hco3-]/[H2CO3])
When HCO3- is reacted with H+ ions this forms CO2 and water, the CO2 is blown off in the lungs however this uses up HCO3-. How is it regenerated?
It is regenerated in the kidneys, it reabsorbs filtered HCO3- and also produces it.
How is absorption of HCO3- in the proximal tubule limited?
It is tubular maximum limited aswell as being limited by the H+ in the tubule that is determined by the Na+/H+ transporter. This means that excess HCO3- is quickly corrected for.
What happens to H+ in the distal tubule?
It is mainly secreted through primary active transport.
Why do h+ ions have to be buffered in the filtrate and how is this done?
This is required to keep the free H+ ion concentration down in the urine. It is achieved by buffering the H+ ions with phosphate (H2PO4-)
What is another ion for buffering H+ in the filtrate?
The ammonia ion NH4+ is in equilibrium with NH3 and hence buffers H+. The ammonium ion is produced in the proximal tubule by conversion of glutamine to glutamic acid to alpha ketoglutarate.
What is a davenport diagram and why is it useful?
It is a diagram showing three lines of constant CO2 and three lines of starting values of HCO3. It is used to look at how changes in pH will affect the concentration of HCO3 for respiratory and metabolic disturbances?
What do the curved upwards lines on the davenport represent and for which cases will they be used?
They are lines of constant CO2 so for a respiratory disturbance you will move between them and then either up or down them depending on the HCO3- levels that are being used to compensate.
What do the straight sloped lines on the davenport diagram represent and what cases will they be used for?
They are lines of varying starting HCO3- so for a metabolic disturbance you will move between them and then side to side depending on the CO2 levels that are being used to compensate.
What is the anion gap?
When all the positive and negative charges in our bodies are added up then the total number of cations (+ve) is slightly bigger than the total number of anions (-ve) so there is an anion gap.
What is the normal range for anion gap and what does a larger anion gap indicate?
3-11mmol.L-1
A high gap means there are a large number of anions not being accounted for:
o Lactate (produced during anaerobic metabolism)
o Ketones (in diabetes or alcohol toxicity)
o sulfates, phosphates, urate, and hippurate (accumulating
during renal failure)
o Aspirin overdose
