Q2 final: Acids + bases Flashcards
(30 cards)
what is neutral pH, plasma pH, and venous vs arterial?
neutral = 7
plasma= 7.4 (7.35-7.45)
venous - slightly below 7.4
arterial- slightly above 7.4
how does co2 supply H+
whats the other H+ source
co2 + h2o-> h2co3 -> H+ + HCO3-
carbonic anhydrase enzyme makes h2co3 from co2 and h2o
other sources; production of inorganic and organic acids by metabolism
what are the 3 lines of defense for resisting [H] changes & how fast do they act?
- chemical buffer systems : immediate
- Respiratory control; a few minutes
- Renal control; hours to days
what is the primary ECF buffer?
H2co3 / HCO3- buffering system. major determinent of plasma ph. (primary against noncarbonic acid changes)
what is the primary ICF buffering system
protein buffer system. also helps with ECF
what is the primary buffer against carbonic acid changes
hemoglobin buffer system
what is the main urinary buffer
phosphate buffer system. it also buffers the ICF
how does ventilation change with metabolic aklalosis/acidosis
acidosis- ventilation increases
alkalosis- ventilation decreases
how does the rate of CO2 removal by the lungs change with metabolc acidosis/alkalosis
increases with acidosis, decreases with alkalosis
how does the rate of h+ generation from co2 change with metabolic acidosis and alkalosis
it increases with alkalosis and decreases with acidosis
what is the most potent acid/base regulatory system n the body; what 3 things does it do
the renal system
- h+ secretion
- HCO3- reabsorption
- NH3 secretion
whats the pH of urine
4.6-8, average is 6
where is na reabsorbed mostly and through what type of channel? where does the energy come from ?
proximal tubule, reabsorbed through Na-H antiporter at the luminal membrane.
-Na-K atpase at basolateral side (blood side) provides the energy
-na is also reabsorbed through the Na-HCO3’ symporter
how does H+ get secreted/whcih channels? what is it linked to?
H+ atpase pump, H-K atpase pumps in type A intercalated tubular cells in the distal and collecting tubules, partly linked to K reabsorption. Also through the Na-H antiporter it is partly linked to Na reabsorption (where does this occur?)
how does hco3 get reabsorbed
hco3 gets filtered as hco3,, turned into H2o and co2 in the tubular lumen by carbonic anhydrase in the lumen (membrane bound). h20 and co2 diffuse into cells of the tube (type a intercalated tubular cells) and then in the cell it can be turned back into hco3- which can be reabsorbed.
how much hco3 gets reabsorbed
the amount that gets filtered equals the amount that gets reabsorbed!
secreted H+ couples with hco3 and forms h2co3-> co2 and h20 which diffuses into thecells of the tubule (then converted back to hco3- in the cell and reabsobred as that
what else does H+ secreted into tube lumen couple with
in addition to HCO3
phosphate, another urinary buffer. it couples with Hpo4 to make h2po4-, and gets EXCRETED that way. (dihydrigen phosphate)
where is hco3 from cellular metabolism reabsorbed
at proximal tubule, distal and collecting tubule. co2 from cell metabolism joins with OH from water, hco3-> reabsorbed
how is NH3 secreted from glutamine. where does it primarily occur? whats this called?
what occurs with every NH4 that gets excreted?
each glutamine is metabolized and turned into 2 nh3 (ammonias) ammoniagenesis !!-mainly occurs in the proximal tubule.
-secreted nh3 binds w/H and forms NH4. for every NH4 excreted, a new hco3 is reabsorbed (this might be because the H is coming from H2co3 that forms hco3 and H in tube cells then secretes the H and the hco3 gets reabsorbed ?
how does HCO3 change with acidosis/alkalosis? (secretion, excretion and reabsorption)
its reabsorption increases with acidosis (its a base) and its reabsorption decreases with alkalosis.
-excretion stays the same with acidosis which means all that is filtered gets reabsorbed. but with alkalosis, excretion starts to occur
what is pk? whats the pk of h2co3
the log of 1k (k is the dissociation constant)
pk of h2co3-6.1
whats the henderson hasselbach equation
pH = pK + log (BASE/acid)
for hco3/co2 its log [hco3]/[co2]
normal [hco3]/[co2] is 20/1 in the blood where
7.4=6.1 + log (x)
logx = 1.3
what are the causes of respiratory acidosis
hypoventilation
- obstruction of airway
- copd
- reduced respiratory muscle ability
in uncompensated RESPIRATORY acidosis what happens to the co2/hco3 levels?
co2 is increased and hco3 is the same as normal
