Acids/bases and buffers-Dr. Lin

Question 1

What are the body’s 3 homeostatic regulators of pH and what order do they respond in?

Answer 1

Chemical buffer systems
1st to respond
Bicarbonate (in ECF); Phosphate (ICF); Protein buffer systems (both ECF and ICF)
remove excess acids or bases
Take < 1 sec (acid/base neutralization & equilibrium shifting)

Respiratory mechanism
2nd  to respond
Takes 1-3 minutes 
Respiratory center involved
Removes CO2  & therefore H2CO3 

Renal mechanism
3rd to respond but most potent
Takes hours to days
Kidneys remove metabolic acids (Pi, uric & lactic acids, ketone bodies)

Question 2

What can change plasma pH? What is the ratio of buffers when plasma pH=7.4?

Answer 2

either the bicarbonate concentration or the PaCO2

plasma pH=7.4 when the buffer ratio is 20/1

Question 3

what happens to plasma pH with an increase in H+?

Answer 3

increase in ventilation=more CO2 exhaled–> shift in curve to the left

if the pH is still too low, the H+ will join NH3 in the kidney to produce ammonium for excretion

Question 4

causes of acidosis and alkalosis

Answer 4

CO2 = Acid (respiratory)
inc CO2 = dec pH (respiratory acidemia)
dec CO2 = inc pH (respiratory alkalemia)
HCO3- = Base (metabolic)
inc HCO3- = inc pH (metabolic alkalemia)
dec HCO3- = dec pH (metabolic acidemia)

pH < 7.35 = Acidemia
pH > 7.45 = Alkalemia

Question 5

what causes respiratory acidosis and how does the body respond?

Answer 5

caused by a retention of CO2 generally caused by respiratory problems: hypoventilation
–> HCO3- remains normal
PaCO2 inc, pH dec.

to compensate, PaCO2 remains high, HCO3- is raised (kidney retains HCO3-) and pH is normalized

Question 6

what causes respiratory alkalosis and how does the body respond?

Answer 6

Excessive loss of CO2 generally caused by hyperventilation
e.g. anxiety, hysteria

Consequences:HCO3- is normal;
PaCO2 is reduced;
pH is raised.

compensation:
PaCO2 remains low;
HCO3- is reduced; HCO3- removed by kidney
pH is normalized.

Question 7

what causes metabolic acidosis and how does the body respond?

Answer 7

Many diseases and medical conditions lead to metabolic acidosis:
-Diabetic ketoacidosis:
accumulation of aceoacetic and hydroxybutyric acids
-Renal failure: kidney unable to retain HCO3-
-Diarrhea: loss of solutes including HCO3-

consequences: PaCO2 is unchanged;
HCO3- is reduced;
pH is reduced.

compensation:
PaCO2 is lowered; the lungs excrete more CO2
HCO3- remains low;
pH is normalized.

Question 8

what causes metabolic alkalosis and how does the body respond?

Answer 8

Example: net loss of
H+: e.g. through vomiting; Ingestion of Soda (NaHCO3)

consequences:
PaCO2 is unchanged;
HCO3- is increased;
pH is increased.

compensation:
HCO3- is raised;
PaCO2 is raised; the lungs excrete less CO2
pH is normalized.