Acid Base Flashcards
(38 cards)
What is pH technically?
the -log[H+]
So the higher the H+ concentration, the ____ the pH and the _____ acidic the fluid is
lower the pH
more acidic
What is the isohydric principle in a nut shell?
Even a small change in H+ concentration will completely alter the isonization state of proteins in the body - particularly bad for enzymes (but also carbs, DNA, RNA, weak acids, etc)
What is Le Chatelier’s Principle in a nut shell?
In an equipibrium equation, if concentration of one of the solutes goes up, the equation will shift away from that solute.
What is the main buffer in the body?
the carbonic acid system:
CO2 + H+ H2CO3 H+ HCO3-
it attenuates any rise in H+
What is normal body pH?
7.4
What is pH typically with respiratory or metabolic acidosis? alkalosis
- 3
7. 5
What are the three types of renal cells involved in renal compensation to an acid base disturbance?
proximal tubule epithelial cell
Type A or alpha intercalated cell
Type B or beta intercalated cell
What is the GOAL of the proximal tubule eptihelial cell in acidosis?
add H+ to the lumen so it gets excreted
What are the two ways the proximal tubule epithelial cell gets H+ into the lumen? Which is mroe prevalent and why?
- stimulates the Na/H antiporter
- stimulates glutaminase, so you get increased proximal ammonium production - ammonium is then exchanged for sodium as well
ammonium is the more important method because you can’t put all that much free H+ in the lumen, toherwise the urine gets acidic and painful (2/3 of the urinary H+ rides out this way)
Do the proximal tubule eptihelial cell can spit H into the urine, blah blah….
What ACTUALLY causes a decrease in H+ in the PLASMA?
If you spit out the hydrogen, something has to happen with the bicarb
turns out the bicarb gets pumped via a Na/bicarb symporter on the basal membrane. thus, bicarb enters the plasma. As bicarb increases in the plasma, lechateleier’s principle kicks in and you get a decrease in H+
How does the alpha intercalated cell respond to acidosis?
It will ramp up activity of the K/H ATPase antiporter and the vacuolar ATPase (which just kicks out H+) so that more H+ gets put in the lumen for excretion
What is the “side effect” of this increased activity to get H in the urine?
K gets reabsorbed, so you get hyperkalemia
Since all the ammonium gets used up in the proximal tubule, whtat is the main urinary buffer once the H+ gets pumped out of the alpha intercalated cell?
phosphate - the HPO4–/H2PO4- system
1/3 of the urinary H+ rides out on H2PO4-
How is the beta intercalated cell related to the alpha intercalated cell?
the beta cell is just the reversed polarity of the alpha cell. It secretes HCO3- and reabsorbs H+ in alkalosis
What is the effect on K+ balance during alkalosis?
remember, the beta cell is active during alkalosis and it’s the opposite polarity from the alpha cell
this means the K+ can only leave the cell on the lUMINAL side now, instead of the basement side. Thus, you excrete more K+ along with the bicarb and you get a hypokalemia
What organ has to compensate for a RESPIRATORY acidosis or alkalosis?
the lungs normally would, but the lungs are what’s malfunctining in a respiratory acidosis or alkalosis.
this means the kidneys have to do the compensation, which takes longer
If the carotid bodies sense an increase in H+ in the plasma, what will they trigger in the respiratory centers? WHy?
They will trigger an increase in respiratory rate
This was lower pCO2 and raise pO2
If you lower pCO2, you shift the buffer reaction to the left. This means the H+ gets used up, and H+ in the plasma decreases = compensation
While the carotid bodies chemoreceptors sense the high H+, what chemoreceptors sense an increase in CO2?
the central chemoreceptors - CO2 easily crosses the BBB, so you get an increase in H+ near the medullary central chemoreceptors
What is the primary disturbance in a respiratory acidosis?
the lungs aren’t working, so you don’t breath out CO2 and it increases
What happens because of the rise in CO2?
the buffer reaction shifts to the right and you get an increase in both H+ and bicarb
results in an acidosis and decrease in pH
What will the renal response be to a respiratory acidosis?
- increase glutaminase and carbonic anhydrase
- stimualte the Na+/H+ antiporter
This means you get more H+ leaving in the urein either freely or on ammonium
this also means you have increased bicarb that gets reabsorbed back into the plasma. The increased bicarb pushes the buffer equation back to the left, causing a dro pin H+ = compensation
Aside - what are normal values on a blood gas report?
bicarb = 27 mM pH = 7.4 pCO2 = 40 mmHg pO2 = 90 mmHg
What will the blood gas results be in a respiratory acidosis?
bicarb HIGH (renal compensation) pH LOW (acidosis) pCO2 HIGH (primary disturbance) pO2 LOW (primary disturbance)
