Two organs, one pH

Science · The Human Body · ages 20-22

Name ______________________ Date ____________

Assume one primary acid-base disorder. Arterial pH is below 7.35 and CO2 is high. Which disorder fits?
- Metabolic alkalosis from increased bicarbonate
- Metabolic acidosis from reduced bicarbonate
- Respiratory acidosis from retained CO2
Which pair connects lung control and kidney control in the bicarbonate buffer system?
- Carbon dioxide and bicarbonate
- Oxygen and the protein hemoglobin
- Sodium and the carbohydrate glucose
Ventilation can adjust CO2 within minutes, while renal adjustment of bicarbonate and acid excretion takes hours to days.
Circle one: True False
Respiratory acidosis persists. Which response provides renal compensation, and over what time?
- The lungs retain more CO2 over several minutes
- The kidneys lower bicarbonate over hours to days
- The kidneys raise bicarbonate over hours to days
Assume one primary acid-base disorder. Arterial pH and bicarbonate are low, and CO2 is also low. Which pattern fits?
- Respiratory acidosis with renal compensation
- Metabolic acidosis with lung compensation
- Respiratory alkalosis with renal compensation
Arterial pH is 7.40, but CO2 and bicarbonate are both abnormal. Which interpretation step is needed?
- Compare the values with expected compensation
- Diagnose a mixed disorder from the pH value alone
- Declare recovery because the pH is in the normal range
If renal compensation raises bicarbonate during respiratory acidosis, the cause of CO2 retention has been removed.
Circle one: True False
Arterial pH is below 7.35, bicarbonate is low and CO2 is high. A student calls the CO2 rise compensation for metabolic acidosis. Which interpretation fits the directions?
- Respiratory acidosis with renal compensation
- Metabolic and respiratory acidosis together
- Metabolic acidosis with lung compensation

Answer key

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Two organs, one pH W1-mt_LFLgZre62C-s1

Respiratory acidosis from retained CO2 · The low pH shows acidemia. High CO2 drives pH downward, so it fits primary respiratory acidosis under the stated single-disorder assumption.
Carbon dioxide and bicarbonate · The reversible buffer reaction connects CO2 with bicarbonate. Ventilation regulates CO2, while kidneys regulate bicarbonate and acid excretion.
True · Ventilation changes CO2 rapidly. Renal adjustment develops over hours to days, with full adaptation taking several days.
The kidneys raise bicarbonate over hours to days · Kidneys increase acid excretion and raise bicarbonate to oppose the acidifying effect of high CO2. Renal compensation develops over hours to days.
Metabolic acidosis with lung compensation · Low bicarbonate lowers pH and fits metabolic acidosis. Lower CO2 opposes that pH change, matching respiratory compensation under the stated assumption.
Compare the values with expected compensation · A pH of 7.40 alone establishes neither recovery nor a mixed disorder. The abnormal values require comparison with expected compensation, duration and history.
False · Raising bicarbonate opposes the effect of retained CO2 on pH. It does not remove the cause of CO2 retention.
Metabolic and respiratory acidosis together · Low bicarbonate and high CO2 both lower pH. The CO2 rise adds a respiratory acidosis instead of opposing the metabolic acidosis.