Question

A: The end of T-wave marks the end of ventricular systole R: T-wave represents ventricular repolarization that leads to the return of ventricles from excited to normal state

• A. (A) and (R) are correct and (R) is the correct explanation of (A).
• B. (A) and (R) are correct but (R) is not the correct explanation
• C. (A) is correct but (R) is not correct.
• D. Both (A) and (R) are not correct.

Answer 1

Answer: (A)

(A) and (R) are correct and (R) is the correct explanation of (A).

Answer 2

The question asks us to evaluate an Assertion (A) and a Reason (R) related to the Electrocardiogram (ECG) and the cardiac cycle.

Assertion (A): The end of T-wave marks the end of ventricular systole.

• In the context of the cardiac cycle and ECG interpretation, ventricular systole refers to the period of ventricular contraction.
• According to the NCERT Class 11 Biology textbook, Chapter 18 "Body Fluids and Circulation", page 288, under the section "Electrocardiograph (ECG)", it is explicitly stated: "The end of the T-wave marks the end of systole."
• Therefore, Assertion (A) is correct as per the standard curriculum for NEET.

Reason (R): T-wave represents ventricular repolarization that leads to the return of ventricles from excited to normal state.

• The T-wave on an ECG represents the electrical repolarization of the ventricles.
• Repolarization is the process where the ventricular muscle cells return to their resting electrical state after depolarization (excitation). This electrical event leads to the mechanical relaxation of the ventricles, allowing them to refill with blood.
• This statement is a fundamental concept in ECG interpretation and is consistent with physiological understanding.
• Therefore, Reason (R) is correct.

Is Reason (R) the correct explanation for Assertion (A)?

• Assertion (A) states that ventricular systole ends at the end of the T-wave.
• Reason (R) explains that the T-wave represents ventricular repolarization, which is the process of the ventricles returning from an excited (contracted) state to a normal (relaxed) state.
• For ventricular contraction (systole) to end, the ventricles must relax. The electrical event leading to this relaxation is repolarization, which is represented by the T-wave. Therefore, the completion of repolarization (end of T-wave) signifies the completion of the contractile phase and the return to a relaxed state, thus marking the end of systole.
• Hence, Reason (R) provides a correct physiological explanation for Assertion (A).

Conclusion:

Both Assertion (A) and Reason (R) are correct, and Reason (R) is the correct explanation for Assertion (A).