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Question 18N.3.SL.TZ0.c

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Date November 2018 Marks available [Maximum mark: 2] Reference code 18N.3.SL.TZ0.c
Level SL Paper 3 Time zone TZ0
Command term Explain Question number c Adapted from N/A
c.
[Maximum mark: 2]
18N.3.SL.TZ0.c

An electrocardiogram (ECG) records the electrical activity of the heart over a period of time using electrodes placed on the skin. The ECG shown is from a patient whose heart was beating irregularly until it was treated using a defibrillator (arrows) which restored normal electrical activity.

Explain what is occurring in the heart during the peak of electrical activity as indicated by the R wave on the ECG.

[2]

Markscheme

a. impulses initiated from the AV node spread across heart ✔

b. impulses travel along Purkinje fibres/across ventricles ✔

c. causing depolarization of the ventricles
OR
that triggers ventricular contraction ✔

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