Chapter 30: Acid-Base Regulation (Discussion 4)

Question 1

Body Fluid pH

Answer 1

ECF pH ~7.35-7.4 (slightly basic) - Much lower and tightly regulated [H+] than [Na+]

ICF pH ~6-7.4 (generally more acidic than ECF)

Question 2

Bicarbonate Buffer System

Answer 2

Most important ECF chemical buffer

Carbonic anhydrase: enzyme that catalyzes H2O + CO2 –> H2CO3

• In nephron primarily located in proximal tubule and collecting tubule (intercalated cells)

H2O + CO2 easily diffuse across membranes but HCO3 cannot

Question 3

Regulation of H+

Answer 3

1. Chemical Buffers (fastest but weakest, doesn’t remove ions from system)
2. Respiratory (Lungs) (Medium strength and speed)
3. Kidneys (slowest but strongest)

Question 4

Chemical Buffers

Answer 4

Bicarbonates

Phosphate (mostly ICF and renal tubular fluid)

Ammonia

Intracellular proteins

Question 5

Respiratory (lungs)

Answer 5

Removal of CO2 - removes H2CO3 from body

Ventilation stimulated by increase in H+ or CO2

Question 6

Kidneys Acid-base Regulation

Answer 6

Excretion of acidic/alkaline urine

• HCO3- reabsorption/regeneration & H+ secretion activity determines urine pH
• Secreted H+ combines w/ tubular HCO3- to reabsorb as H2O + CO2
• Highly acidic urine formed by active secretion of H+ (mostly bound to other buffers) by intercalated cells

Question 7

Acidosis

Answer 7

Decrease in pH due to increase in H+

• Respiratory: decrease ventilation –> increase P_CO2 and increase HCO₃-
• Metabolic: decrease P_CO2 and decrease HCO₃-

Causes:

• Renal tubular acidosis
• Diarrhea
• Vomiting of intestinal contents
• Diabetes mellitus (fat metabolism –> acetoacetic acid)
• Ingestion of acids
• Chronic renal failure

Treatment:

• NaHCO3 (oral)
• Sodium lactate/glutamate (IV)

Question 8

Alkalosis

Answer 8

Increase in pH due to decrease in H+

Respiratory: increase ventilation –> decrease PCO2 and decrease HCO3-

Metabolic: increase PCO2 and increase HCO3-

Causes:

• Diuretics
• Excess aldosterone
• Vomiting of gastric (without lower intestinal) contents
• Ingestion of alkaline drugs

Treatment:

• Ammonium chloride (orally)
• Lysine monohydrochloridic (IV)

Question 9

Determining Respiratory vs Metabolic

Answer 9

One is source, the other compensates