The sinoatrial node (SAN) and the atrioventricular node (AVN) have an important role in the control of the cardiac cycle. The timing of atrial and ventricular systole and diastole must be controlled so that blood passes through the heart efficiently. Impulses sent out by the SAN pass to the AVN, where there is a short delay. With reference to Fig. 1.1, explain why it is important for the control of the cardiac cycle that there is a short delay at the AVN after impulses have been sent out by the SAN.

Biology

IGCSE&ALevel

CAIE

Exam No：9700_s23_qp_22 Year：2023 Question No：1(b)

Answer:

allow responses in context of both sides or one side of heart

any two from:

atria and ventricles, do not contract/ are not in systole, at the same time ; AW

ventricles, contract / are in systole, after atria ; AW ora

idea that allows atria to empty (completely) / allows ventricles to fill ;
A idea that (all) blood, pumped / AW, into ventricles (ready for systole)

Knowledge points:

8.3.1 describe the external and internal structure of the mammalian heart

8.3.2.1 atria and ventricles

8.3.2.2 left ventricle and right ventricle

8.3.3 describe the cardiac cycle, with reference to the relationship between blood pressure changes during systole and diastole and the opening and closing of valves

8.3.4 explain the roles of the sinoatrial node, the atrioventricular node and the Purkyne tissue in the cardiac cycle (knowledge of nervous and hormonal control is not expected)

Answer:

Knowledge points:

Solution:

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