Fig. 3.1 and Fig. 3.2 are diagrams of transverse sections of the human heart during different stages of the cardiac cycle. The sections pass through the heart at a level that is just above the valves. [Figure 3.1] [Figure 3.2]

Mark scheme

Marking points from the official mark scheme (Feb/Mar 2025). The mark or mark type is shown in brackets.

1. [1] semi-lunar valve ; accept aortic valve / pulmonary valve
2. [2] 1 from the atria to the ventricles ; 2 into the (left and right) atria from the pulmonary vein and vena cava ; A venae cavae for vena cava A superior vena cava and inferior vena cava
3. [2] stage of cardiac cycle: ventricular systole ; reason: bicuspid / mitral, valve and tricuspid valve closed or atrioventricular valves closed or semi-lunar valves / aortic and pulmonary valves, open ;
4. [3] any three from: 1 impulses reach the atrioventricular node ; 2 short delay / after 0.1 s ; 3 (AVN) sends impulses through, Purkyne fibres / Bundles of His ; A Purkinje for Purkyne 4 impulses (travel down through the septum and) reach the, base / apex, of the ventricles / heart ; 5 impulses travel upwards / AW, causing ventricles to contract from base upwards; 6 atria complete contraction / atria and ventricles do not contract at the same time / ventricles fill with blood / atria empty; 7 ref. to (both) ventricles contract at same time ;