Jenny is an insulin-dependent diabetic. She was admitted to the hospital in a co
ID: 181123 • Letter: J
Question
Jenny is an insulin-dependent diabetic. She was admitted to the hospital in a coma with ketonuria because she had not taken her insulin. Ketonuria occurs when ketones (which are acids) are added to the systemic circulation by the liver, and the plasma ketone level rises high enough (ketonemia) that the kidneys cannot excrete them all.
A) At the onset of her ketonemia, how was arterial pH changed? Is it higher or lower? Explain.
B) The body’s first compensatory response is respiratory compensation. In this particular case, what receptors trigger this respiratory change, and what is the stimulus for that compensation?
C) How will arterial Pco2 and arterial pH change after respiratory compensation ensues? Explain.
Explanation / Answer
A) At the onset of her ketonemia, the arterial pH decreases because the ketone bodies in the circulation causes ketoacidosis. This is also known as "diabetic ketoacidosis."
B) The increased acidity in the blood (increased concentration of hydrogen ions) triggers the chemoreceptors in the medulla oblongata. This results in increased rate of respiration. So the exhalation of carbon dioxide decreases the formation of carbonic acid and raise the pH.
C) After respiratory compensation, the arterial Pco2 reduces and arterial pH increases (moves toward neutral or less alkaline pH)
One of the important transport mechanism of CO2 is, the formation of carbonic acid. The increased PCO2 in the blood results in increased formation of carbonic acid (H2CO3) in the presence of carbonic anhydrase. The carbonic acid dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-).
CO2 + H2O <-----> H2CO3 <-----> H+ + HCO3-
The formed hydrogen ions readily bind to deoxyhemoglobin present in the systemic circulation, which buffer the blood pH.
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