Question

In normal ECG, PR and T waves are lie at _________
A. Above the baseline
B. Below the baseline
C. Partly above and partly below the baseline
D. Equal to the baseline

Answer 1

An electrocardiograph is a machine which is used to obtain an electrocardiogram. It is a representation of the graph of the electrical activity of the heart during a cardiac cycle. It used to determine the rhythm of the heart and other conditions related to the heart.

Complete answer:
The electrocardiograph records the electrical impulses i.e.the change in the electrical impulses of the heart, and plots it on a graph. It is a graph between the voltage and the time of the electrical activity of the heart using electrodes placed on the skin. These electrodes help in the detection of small electrical changes that are results of cardiac muscle depolarization followed by repolarization during each cardiac cycle. The readings of a particular individual ECG are compared with a standard ECG to evaluate the working of the heart and checking it for any abnormalities. The ECG is identified from a letter P to T which corresponds to a specific activity of the heart.
An electrocardiograph, the P-wave represents the electrical excitation of the atria, which leads to the contraction of both the atria. The QRS complex represents the depolarization of the ventricles which starts the ventricular contraction. The contraction starts shortly after Q and marks the beginning of the systole. The T-wave represents the return of the ventricles from elevated to a normal state. The end of the T-wave marks the end of the systole. The QRS complex gives the idea of the rate of the heartbeat. In the normal ECG, the PR and T lie above the baseline.
Hence, the correct answer is ‘A. Above the baseline’.

Note: The normal range of ECG is 120-200 ms. The horizontal lines of the graph represent the time interval and the rate of the heart. The improper reading of ECG referred to as arrhythmia.