Draw a standard ECG and explain the different segments in it.

Explanation

ECG has 5 waves or deflections which are conventionally designated as PQRT. The five waves have a horizontal part in the beginning as well as inside. It is called isopotential or baseline. PR, and T waves lie above the horizontal line. They are called positive waves. Q, and S waves lie below the horizontal line, and are therefore called negative waves. P represents the development of action potential at the sinoatrial node, and the spread of impulse throughout the atria. The atrial muscles become depolarized. After a fraction of a second, the next complex of QRS begins with a small downward or nevative reflection of Q. QRS represents depolarisation of atrial muscles and depolarisation of ventricular muscles. Its different components are PQ, QR and RS . PQ indicates contraction of atria. QR provides information about spread of cardiac from SA node to AV node. RS gives information about pread of impulse from AV node to purkinje fibers, and ventricular depolarization. It initiates contraction of ventricles. Ventricular contraction continues during ST part . It is followed by the relaxation of ventricles and development of the repolarisation wave.