. Which of the following accurately describes the relationship between PCO2 and blood pH?
There is no relationship between PCO: and pH
They are directly proportional: as PCO: increases, pH increases
They are inversely related: as PCO: increases, pH decreases
PCO2 only affects pH if bicarbonate levels are high
The Correct Answer is C
A. There is no relationship between PCO2 and pH: Carbon dioxide acts as a volatile acid precursor in the blood through its hydration into carbonic acid. Changes in its partial pressure directly shift the chemical equilibrium of the bicarbonate buffer system. It is the primary respiratory determinant of systemic acidity.
B. They are directly proportional: as PCO2 increases, pH increases: Increasing carbon dioxide levels leads to the production of more hydrogen ions, which lowers the pH of the solution. A direct proportion would imply that more CO2 makes the blood more alkaline. This contradicts the fundamental chemistry of the carbonic acid equilibrium.
C. They are inversely related: as PCO2 increases, pH decreases: Higher concentrations of dissolved carbon dioxide generate more carbonic acid, which dissociates and raises the concentration of free protons. This increased acidity is reflected as a lower numerical pH value. This inverse relationship defines the mechanism of respiratory acidosis.
D. PCO2 only affects pH if bicarbonate levels are high: The hydration of carbon dioxide occurs regardless of the initial bicarbonate concentration. While bicarbonate acts as a buffer to mitigate pH changes, the addition of CO2 will always push the equilibrium toward acid production. It is an independent variable in Henderson-Hasselbalch dynamics.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
False: Diuresis is the elevated excretion of urine, which typically follows the ingestion of large fluid volumes or the use of certain medications. It is the body's method of shedding excess water to maintain euvolemia. The term represents an increase, not a decrease, in renal output.
Correct Answer is B
Explanation
A. In the digestive tract: While potassium is ingested through the diet, it is rapidly absorbed into the bloodstream and then sequestered into cells. The lumen of the gut does not serve as a primary storage site. Most potassium is located within the soft tissues.
B. In the intracellular fluid (ICF): Approximately 98% of total body potassium is sequestered within the cells, primarily in skeletal muscle. This high internal concentration is maintained by the active transport of the Na+/K+-ATPase pump. It is essential for maintaining the resting membrane potential.
C. In the extracellular fluid (ECF): Plasma potassium represents only a tiny fraction of the total body store, usually measured between 3.5 and 5.0 mmol/L. Even minor shifts in this ECF concentration can have lethal effects on cardiac rhythm. The ECF is not a reservoir.
D. In the renal filtrate: The kidneys filter potassium, but the vast majority is reabsorbed in the proximal tubule and Loop of Henle. The amount present in the filtrate at any given time is minimal. The renal system manages the narrow margin of potassium excretion.
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