Peak $T$ - initiation of total cardiac contraction
Peak $P$ and peak $R$ together - systolic and diastolic blood pressures
Peak $P$- initiation of left atrial contraction only
Show Solution
The Correct Option isA
Solution and Explanation
An electrocardiogram (ECG) is a graphical representation of the electrical activity of the heart. Each component of the ECG reflects a specific part of the cardiac cycle:
P wave: Represents the initiation of atrial depolarization, which is the contraction of both the left and right atria. It does not represent the contraction of the left atrium only.
QRS Complex: Represents ventricular depolarization, which is responsible for triggering the contraction of the ventricles. This complex corresponds to one complete pulse, from the start of ventricular depolarization to its end. Therefore, the correct interpretation is "Complex QRS - one complete pulse."
T wave: Represents ventricular repolarization, not the initiation of cardiac contraction. It is the phase where the ventricles start relaxing after the contraction.
Let's evaluate the options:
Complex QRS - one complete pulse: This option is correct as it accurately describes the function of the QRS complex.
Peak T - initiation of total cardiac contraction: Incorrect, as the T wave represents ventricular repolarization, not contraction initiation.
Peak P and peak R together - systolic and diastolic blood pressures: Incorrect, as these peaks are electrical signals, not pressure measurements.
Peak P - initiation of left atrial contraction only: Incorrect, since the P wave represents both atria's depolarization.
