Read the following statements regarding the standard electrocardiogram (ECG) and the cardiac cycle: A. The P-wave represents the electrical excitation of the atria. B. Ventricular contraction starts shortly after the Q wave. C. The T-wave represents the depolarisation of the ventricles. D. By counting the number of QRS complexes that occur in a given time period, one can determine the heart beat rate of an individual

Step-by-step solution

Statement A is correct: The P-wave represents the electrical excitation (or depolarisation) of the atria, which leads to the contraction of both the atria. Statement B is correct: The QRS complex represents the depolarisation of the ventricles, which initiates the ventricular contraction. The contraction starts shortly after Q and marks the beginning of the systole. Statement C is incorrect: The T-wave represents the return of the ventricles from an excited to a normal state (repolarisation), not depolarisation. St