Question

Match List-I with List-II
\begin{tabular{ll} List-I (ECG waves/Heart Sounds) & List-II (Indication)
(A) P wave & (I) Closure of AV valves
(B) QRS complex & (II) Atrial depolarization
(C) First heart sound & (III) Closure of semilunar valves
(D) Second heart sound & (IV) Ventricular depolarization

Choose the correct answer from the options given below:

• (A) - (II), (B) - (I), (C) - (IV), (D) - (III)
• (A) - (II), (B) - (IV), (C) - (I), (D) - (III)
• (A) - (III), (B) - (I), (C) - (II), (D) - (IV)
• (A) - (IV), (B) - (III), (C) - (II), (D) - (I)

Hint:

S1 ("Lubb") is always associated with the closure of the AV valves (start of systole).
S2 ("Dupp") is always associated with the closure of the semilunar valves (start of diastole).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Electrocardiogram (ECG) waves and heart sounds represent different electrical and mechanical events during the cardiac cycle.

Step 2: Detailed Explanation:
Let us match each cardiac event with its indication:
- (A) P wave: Represents the spread of electrical excitation across the atria, which is Atrial depolarization (II).
- (B) QRS complex: Represents the electrical excitation of the ventricles, which is Ventricular depolarization (IV). This triggers ventricular contraction.
- (C) First heart sound (S1 - "Lubb"): Caused by the vibration associated with the Closure of the atrioventricular (AV) valves (I) (tricuspid and mitral valves) at the start of ventricular systole.
- (D) Second heart sound (S2 - "Dupp"): Caused by the vibration associated with the Closure of the semilunar valves (III) (aortic and pulmonary valves) at the start of ventricular diastole.
This gives the matching sequence: (A)-(II), (B)-(IV), (C)-(I), (D)-(III).

Step 3: Final Answer:
The correct matching sequence is (A) - (II), (B) - (IV), (C) - (I), (D) - (III), corresponding to Option (B).