Depolarisation of atria is represented by:

Question

Accepted Answer

The correct option is 1:

The P-wave on an electrocardiogram (ECG) is the first deflection from the baseline and represents the electrical activity associated with atrial depolarization. Depolarization is the electrical activation of the heart muscle cells that precedes contraction. In simpler terms, it's the electrical signal that tells the atria (the upper chambers of the heart) to contract and pump blood into the ventricles. This initial electrical event originates in the sinoatrial (SA) node, the natural pacemaker of the heart, and then spreads across both the right and left atria, leading to their synchronous contraction. A normal P-wave indicates that this atrial depolarization is occurring correctly and that the SA node is initiating the heart's rhythm.

The incorrect option is 2:

The Q-wave is the first downward deflection of the QRS complex. It represents the initial depolarization of the interventricular septum. While it's part of ventricular depolarization, it does not represent atrial depolarization.

The incorrect option is 3:

The T-wave represents ventricular repolarization, which is the electrical recovery of the ventricles. It signifies the relaxation of the ventricular muscle after contraction, not the depolarization of the atria.

The incorrect option is 4:

The QRS complex represents ventricular depolarization, which is the electrical activation of the ventricles. This massive electrical event leads to the contraction of the ventricles and the pumping of blood to the body. While a crucial part of the cardiac cycle, it directly follows atrial depolarization and masks the simultaneous atrial repolarization, and thus does not represent atrial depolarization.