The Electrocardiogram (ecg)

5. How does exercise (work) affect your heart rate and blood pressure and what is the influence of the rate of exercise (work rate) on these changes? Comment on the size of the change in blood pressure during exercise in relation to the systolic pressure, the diastolic pressure and the mean arterial pressure.

6. What effect would you expect training to have on (a) the increase in heart rate during exercise, and (b) how quickly it returns to normal after exercise?

THE ELECTROCARDIOGRAM (ECG)

In the space below place a copy of the recording of the ECG of yourself or one member of your group showing at least 4 or 5 cardiac cycles. Identify the P, QRS and T waves of the ECG.

NOTE: The ECG traces you will be recording will be through the LabTutor program. If you email the report page of the ECG exercise to yourself (by clicking the ‘email’ link in the report page of LabTutor), you will receive a Word document of all your graphs. Keep in mind that you will need to make any adjustments to your graph in the LabTutor interface before emailing a copy to yourself. If you are not able to do this in the lab practical, your experiment data will be available by logging into LabTutor from any Physiology computer.

Example ECG Traces

1. What do each of these waves of the ECG represent and at which stage of the cardiac cycle do they occur?

2. Why does the QRS complex have the largest amplitude?

3. Explain why the ‘lub’ sound occurs at the time of the QRS complex

4. Explain why the ‘dup’ sound occurs at the time of the T wave.

On the following page are some illustrative examples of ECG recordings. Trace A is a normal recording. Traces B, C and D each illustrate some abnormality of the ECG. For each of these traces comment on any unusual features of the recording that you notice and suggest what the underlying abnormality might be.

Trace A – Normal ECG Recording

Trace B

Briefly describe how this trace differs from