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Group 2: 3. Fill in the name of the ECG phase/wave that corresponds to each of t

ID: 3479497 • Letter: G

Question

Group 2: 3. Fill in the name of the ECG phase/wave that corresponds to each of the following cardiac events, and indicate the phase of the cardiac cycle with which it corresponds. For each of the phases describe () what is happening within the ventricle (i.e. what is the state of the muscle), (ii) what is happening to pressure, (ii) what is happening to volume, and (iv) are the valves open/closed. In addition, draw a typical ECG trace, labeling each of the waves and their intervals. Cardiac Event ECG phase/waveCorresponding cardiac cycle phase Ventricles repolarize Atria depolarize

Explanation / Answer

Ventricles depolarize; Q ,R, S wave

As the ventricles undergo depolarization, ventricles undergo systole. As the ventricular systole begins, pressure in ventricles rises immediately to exceed the pressure in auricles. With this pressure AV valves are shut sharply.

Ventricles repolarize; T wave.

In ventricular repolarization, ventricles go into diastole and start relaxing. At this time ,auricles are still in diastole, so all the chambers of heart are in diastole. This is called joint diastole. During ventricular diastole pressure falls in ventricles below the pressure in great arteries so the SL valves are immediately shut down to prevent any back flow of blood.

Atria depolarize; P wave.

In the atrial depolarization, the two auricles contract simultaneously and forces blood to their respective ventricles. Blood enters from auricle into ventricle through AV apertures.