Exam3Lec7AcidBase2 Flashcards
Total acid production=____ + ____
Volatile Acid (99.8 %)+Fixed Acid (0.02 %)
What does the davenport diagram show?
- It is a graphical visualization of the HH equation.
- pH-Bicarbonate Diagram with PCO2 Isobars
- By changing PP of CO2 and measuring pH and bicarb you can get different points and put them together to get the normal buffer line.
Is the red solid line or the black solid line a more powerful buffer? Why?
red line is a more powerful line because for example when the pp changed from 40 to 80, pp change when from 7.4 to 7.2. The black line change more, pH went from 7.4 to 7,15
What makes blood a better buffer and how?
Hemoglobin makes blood a better buffer and increases bicarbonate concentration
Which buffer system is more powerful (left vs right graph) and why?
The right graph is more powerful because it represents HCO3-/H2CO3 biffer system with hemoglobin.
As seen on the graph and using the HH equation, then change in the pH is less as pp CO2 incr. It keeps the overall ratio of [HCO3-]/[CO2] relatively the same bc as CO2 incr so does HCO3-. Same for decr.
Explain transport of CO2 and buffering by hemoglobin
why when blood has hemoglobin our plasma buffering system is more powerful?
Because Most CO2 is transported in the blood as HCO3-
incr CO2 concentration, incr bicarb concentraiton in plasma,
Regulation of Body pH is achieved by what 3 mechanisms?
- Chemical Buffering
- Respiratory Compensation (lungs)
- Renal Compensation (kidney)
ADDITION OF A STRONG ACID
Lets say that there is an addition of HCL to the plasma (final: 12 mM HCl). Explain the First Line of Defense (fast chemical buffering) with the HH equation. How does the pH change?
pH went from 7.4-6.06 with the fast chemical buffering
ADDITION OF A STRONG ACID
Explain acidosis and our second line of defense** (fast respiratory component)** with the HH equation. How does the pH change?
- With regular ventilation: . The increased [CO2] by buffering is removed by alveolar ventilation, so PCO2 is maintained at 40 mmHg (1.2 mM CO2) and pH goes up to 7.1
- Acidosis causes incr in ventilation, so PCO2 decr from 40 to 25 (0.75). pH incr to 7.3 which is closer to 7.4
Explain acidosis and our third line of defense (Slow Renal Compensation) with the HH equation. How does the pH change?
Here H+ secretion and HCO3- reabsorption is occuring and Over a period of days plasma HCO3- returns to normal. pH comes back to 7.40
Restoration of [HCO3-], Restoration of [CO2]
How can the kidney bring bicarb concentration from 12mmol back to 24 mmol?
By H+ secretion and HCO3- reabsorption through renal transporters of HCO3- and H+
What are 3 main mechanisms of H+ secretion and note their location on the nephron.
- H+ exchanged for Na+ ( HCO3- reabroption)- at the PT
- H+ ATPase and H+K+ATPase in DT and CT
Bicarbonate reabsoprtion primary in ____ and does ____ % of acid excretion
PT, 0%
How does bicarbonate reabsoprtion occur in the PT and how is there is no acid excretion?
Bicarbonate Reabsorption
(Proximal Tubule)
Summary
____ of Na+ and HCO3-
____ secretion of H+
____ tubular pH
Net reabsorption of Na+ and HCO3-
No net secretion of H+
No change in tubular pH
What enhances Na+/H+ exchange in the PT and what are the limits of Net reabsorption of Na+ and HCO3- in the PT?
- ATII enhances Na+/H+ exchange
- Limits: If filtered load of HCO3- exceeds ~40 mM, the reabsorption mechanism becomes saturated.
Review: what are the non-volatile acids (fixed acids) produced by the human body?
H+ + HPO42-
H+ + SO42-
Explain Titratable acid excretion
Lxn?
Acid excretion %?
- Proton is being actively pumpped into lumen using ATP and binds to fixed acids and the proton is excreted and bicarb is regenerated
- Primarily in Distal Tubule & CD
- Accounts for 33 % of Acid Excretion
every time you secrete a prton you generate a new bicarb
Explain Ammonium excretion
Lxn?
Acid excretion %?
[H+]?
- H+ is pumped into the lumen and it binds to NH3 (ammonia). This now becomes NH4+ whihc is membrane impermeable so it becomes excreted. Bicarb is regenerated
- Primarily in Distal Tubule & CD
- Accounts for 66 % of Acid Excretion
- [H+] is 1000 X greater in the lumen than the cell
[H+] is 1000 X becuase H+ is accumulating in the lumen and tubular fluid becomes very acidic
Name what each slope represents
respiratory acidosis/alkalosis is due to ____
metabolic cidosis/alkalosis is due to ____
respiratory acidosis/alkalosis is due to CO2
metabolic cidosis/alkalosis is due to HCO3-
What causes respiratory acidosis?
Any impairment of alveolar ventilation.
1) COPD, CHF and other lung diseases.
2) Anesthetics and Drugs
What occurs to pH and CO2 in respiratory acidosis?
pH decr due to incr CO2
Chronic respiratory acidosis has some metabolic compensation. How does this work?
Kindey would help by incr concentration os bicarb to incr bicarb reabsorb so pH can incr.
