'A' Level Medical Option Questions - The Heart - ECG
Q6.
(a) Sketch a graph of the ECG trace for a healthy heart. Label each axis with appropriate units and scales.
time/seconds on x-axis and potential/ mV on y-axis 
correct value on x axis (between 0.9 and 1.0 s to end of trace)
correct values on y axis (start at 0, highest point between 0.8 and 1.0 mV)
shape of curve - you were not asked for the letters - but they are useful to add!
4 marks
(b) When obtaining such a trace, electrodes are attached to the patient. State and explain two precautions which should be taken when attaching the electrodes to ensure reception of the best signal.
precaution |
explanation |
attach firmly |
stop noise |
| remove dead skin/hair |
reduce contact resistance |
use conducting gel |
remove air for better electrical contact |
positioning of electrodes |
to get largest pd |
2 marks maximum
Total 6 marks
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