Which of the following is not a chemical barrier?
enzymes
complement
interferons
ciliated epithelium
The Correct Answer is D
A. enzymes: many enzymes (e.g., lysozyme in saliva/tears) are chemical barriers to microbes.
B. complement: the complement system is a set of plasma proteins that chemically attack pathogens (a chemical innate defense).
C. interferons: interferons are signaling proteins that help inhibit viral replication and are considered chemical immune defenses.
D. ciliated epithelium: ciliated epithelium is a physical/mechanical barrier (moves mucus and trapped particles), not a chemical barrier.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. QRS complex: The QRS represents the rapid depolarization of the right and left ventricles (electrical activity that triggers ventricular contraction).
B. T wave: The T wave represents ventricular repolarization (the ventricles recovering electrically), not depolarization.
C. P wave: The P wave represents atrial depolarization, the electrical activation of the atria.
D. PQ segment: The PQ (PR) segment is the brief isoelectric period while the impulse travels through the AV node/AV bundle (a conduction delay), not ventricular depolarization.
Correct Answer is C
Explanation
A. It causes extreme depression of the respiratory rate: CO binds hemoglobin and impairs O₂ delivery; respiratory depression is not the primary danger
B. It drastically decreases the pH of the blood: CO poisoning does not primarily cause a dramatic blood pH drop
C. It binds to the oxygen-binding site on hemoglobin, so the O₂-carrying ability of the blood is reduced: CO binds avidly to hemoglobin’s heme sites, displacing O₂ and reducing oxygen carriage and delivery
D. It triggers hyperventilation, causing a severe drop in PCO₂ and increase in blood pH: Hyperventilation is not the main mechanism of CO toxicity
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