Which of the following correctly explains a phase/event in the cardiac cycle in a standard electrocardiogram?
(a) QRS complex indicates atrial contraction.
(b) QRS complex indicates ventricular contraction
(c) Time between S and T represents atrial systole.
(d) P-Wave indicates the beginning of ventricular contraction.

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Solution

Option (b) QRS complex indicates ventricular contraction

QRS Complex QRS wave (complex) begins after a fraction of second after the P wave. It begins as a small downward deflection (Q) and continues as a large upright (R) and triangular wave, ending as downward wave (S) at its base.
This represents ventricular depolarization (ventricular contraction). Thus, the other options are wrong.

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Match column I with column II regarding the standard ECG of a normal person.
$\begin{matrix} C o l u m n - I & C o l u m n - I I (a) & P - w a v e & (i) & A t r i a l d e p o l a r i z a t i o n (b) & Q R S w a v e & (i i) & V e n t r i c u l a r d e p o l a r i z a t i o n (c) & T w a v e & (i i i) & V e n t r i c u l a r r e p o l a r i s a t i o n \end{matrix}$

Q. Arrange the following events in the correct order.

I. Atrial systole
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III. Joint diastole
IV. Ventricular systole
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Which of the following correctly explains a phase/ event in cardiac cycle in a standard electrocardiogram?

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