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In a standard ECG which one of the following alphabets is the correct representation of the respective activity of the human heart?
A
P – depolarisation of the atria
B
R – repolarisation of ventricles
C
S – start of systole
D
T – end of diastole
Detailed Solution
The P-wave represents the electrical excitation (depolarisation) of the atria, which leads to the contraction of both atria. This is correct.
The QRS complex (including R and S) represents the depolarisation of the ventricles, which initiates ventricular contraction; the contraction starts shortly after Q and marks the beginning of systole. So R is not repolarisation, and S is not the start of systole.
The T-wave represents the return of the ventricles from the excited to the normal state (repolarisation); the end of the T-wave marks the end of systole, not of diastole.
Hence the correct representation is P – depolarisation of the atria.
The QRS complex (including R and S) represents the depolarisation of the ventricles, which initiates ventricular contraction; the contraction starts shortly after Q and marks the beginning of systole. So R is not repolarisation, and S is not the start of systole.
The T-wave represents the return of the ventricles from the excited to the normal state (repolarisation); the end of the T-wave marks the end of systole, not of diastole.
Hence the correct representation is P – depolarisation of the atria.