A-LevelBiologyTransport in mammals9700/23 · May/June 2022 · Q65 Marks

The sinoatrial node, atrioventricular node and the Purkyne tissue have important roles in the cardiac cycle.

(a)State the precise location in the heart of the sinoatrial node.[1]
(b)State the part of the cardiac cycle that is directly initiated by the wave of excitation sent out by the sinoatrial node.[1]
(c)Part of the control of the cardiac cycle involves the contraction of the ventricle walls after the walls of the atria have finished contracting. Outline how this control is achieved.[2]
(d)Name the valves of the heart that open soon after the Purkyne tissue has received an impulse from the atrioventricular node.[1]

Mark scheme

Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.

[1] wall / muscle, of right atrium ;
[1] atrial, systole / contraction;
[2] AVN delays impulse (from sinoatrial node / atrial muscle); AW e.g. excitation wave / conduction plus one from: ring of non-conducting fibrous tissue prevents impulse from sinoatrial node directly passing to ventricles ; impulse must pass through, atrioventricular node / AVN ; (then) passes to Purkyne tissue (to ventricles for contraction);
[1] semi-lunar (valves) ; A aortic valve and pulmonary valve

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