ECG depicts the depolarisation and repolarisation processes during the cardiac cycle. In the ECG of a normal healthy individual one of the waves is not represented. Which wave is that? Explain.

Hint: ECG is a test which records the electrical activity in the heart. This activity is recorded in the form of a graph which shows the path of electrical signal travelling through the heart. The graph generated is known as electrocardiogram.

Complete answer:
To answer this question, we must know about the waves generated in electrocardiograms. The ECG is a representation of the path of the action potential in the heart chambers. It is shown in the form of a wave diagram. It is a graph of voltage versus electrical activity in the heart.

The ECG wave of a normal heart consists of waves which consist of PQRST.The wave P represents the depolarisation in the atrial muscles as these muscles are in the state of excitation in response to stimulus. The wave QRS is the longest wave which represents depolarisation in the ventricles. Along with the depolarisation, ventricular repolarization in the atrium takes place. This repolarisation is not represented by any wave in the ECG.

The T wave is the last wave which represents the repolarization in the ventricles. This takes place when the ventricles come down from the excited state to normal state.The normal ECG values are RR interval: 0.6-1.2 seconds, P wave: 80 ms, PR interval is 120-200ms. The answer is Repolarization of atrium.

Note: ECG is helpful in determining abnormalities in the heart. The heart attack, cardiac stress, shortness of breath, murmurs, seizures, palpitations etc can be diagnosed through ECG. It is also helpful in pre-operative and post-operative assessment. It is also helpful in medicine management and drug administration.