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Date November 2018 Marks available 2 Reference code 18N.3.SL.TZ0.17
Level Standard level Paper Paper 3 Time zone TZ0 / no time zone
Command term Outline Question number 17 Adapted from N/A

Question

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.

State how many normal heartbeats are shown in the ECGs.

[1]
a.

Outline how a defibrillator is used to restore normal heartbeat.

[2]
b.

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

[2]
c.

Markscheme

8 ✔

a.

a. «paddles/electrodes/defibrillator» deliver an electric shock to the heart ✔

b. depolarizes cardiac muscle ✔

c. enables the pacemaker/SA node to regain control ✔

b.

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 ✔

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Option D: Human physiology » Option D: Human physiology (Core topics) » D.4 The heart
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Option D: Human physiology » Option D: Human physiology (Core topics)
Option D: Human physiology

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