Immunoglobulins of class IgA are produced by plasma cells and:

Correct Answer: C

Rationale: IgA, found in mucosal secretions (e.g., saliva, tears), protects the GI, urogenital, and respiratory tracts against pathogens. IgM and IgG fight blood infections, and IgE is linked to allergies.

Correct Answer: C

Rationale: In complete heart block (third-degree), all impulses are blocked at the AV node (C), causing ventricles to beat independently at 20-40 bpm via Purkinje fibers, not 60 (A). The SA node functions normally (B is false), and BP is typically low (hypotension) due to bradycardia, not high (D). (Source: Document, p. 6-7)

Correct Answer: C

Rationale: An electrocardiogram (ECG, C) records the heart’s electrical activity via skin electrodes, showing rhythm and conduction. A (eye movement), B (brain activity), D (ultrasound imaging), and E (muscle activity) are unrelated to this function.

Correct Answer: A

Rationale: The aorta (A) carries oxygenated blood from the left ventricle to the body. The pulmonary artery (B) carries deoxygenated blood from the right ventricle, pulmonary vein (C) to the left atrium, and superior vena cava (D) to the right atrium.

Correct Answer: A

Rationale: The P wave (A) represents atrial depolarization. QRS (B) is ventricular depolarization, T wave (C) is ventricular repolarization, and PQ interval (D) is a time segment, not a wave.