CAIE A-Level Biology AS 8.3.4 Cardiac Conduction System Questions
Explain how the cardiac conduction system coordinates heart contraction using evidence from each question and mark scheme.
- Syllabus
- 2028–2030
- Course
- Biology 9700
- Level
- AS
Exam points
- Explain the cardiac conduction system and how it coordinates heart contraction.
CAIE A-Level Biology AS 8.3.4 Cardiac Conduction System Questions question 1
[Maximum number: 3]
Control of heartbeat is myogenic. This means the electrical activity controlling the rhythm of a regular heartbeat begins in the heart muscle itself.
Atrial fibrillation (AF) is an abnormal heart rhythm that causes rapid and irregular contractions of the atria. Untreated cases of AF can lead to a stroke.
A common cause of AF is when a small group of muscle cells in the wall of the left atrium starts to send out electrical impulses to the surrounding heart muscle cells.
Explain how the control of heartbeat by the sinoatrial node can be disrupted by AF , resulting in rapid and irregular atrial contractions.
any three from:
1 normally only SAN in (wall of) right atrium sends out impulses ;
2 ref. to extra impulses (from wall of left atrium) ;
3 atrial systole might occur when it should be in diastole ;
4 impulses interfere with each other / AW ;
5 SAN no longer able to act as a pacemaker ;
6 rapid since extra contractions ;
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