A-LevelBiologyTransport in mammals9700/22 · Feb/Mar 2018 · Q56 Marks

The sinoatrial node (SAN) and the atrioventricular node (AVN) are two regions of the heart. Fig. 5.1 shows features that are observed in transverse sections of the three main types of blood vessel. [Figure 5.1]

(a)Outline the roles of the SAN and the AVN in the initiation and control of heart action.[3]
(b)(i)Complete Fig. 5.1 by stating the type of blood vessel indicated by D, E and F.[1]
(b)(ii)The inner layer of the walls of D and E is composed of endothelial tissue. List two structural features of this tissue.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Feb/Mar 2018). The mark or mark type is shown in brackets.

[3] any three across both sections: SAN (max two): 1 pacemaker/sets rate of heart beat / responsible for rhythmic contraction; 2 sends out, impulses / waves of excitation / waves of depolarisation; 3 initiates/brings about / AW, heart beat / contraction of the heart / atrial contraction / atrial systole ; AVN (max two): 4 acts to relay impulses / described ; 5 introduces delay to ventricular, systole / contraction(s) / prevents simultaneous contraction of atria and ventricles / AW ; A allows time for, atria to empty / ventricles to fill 6 conducts, waves of excitation / impulses, to, bundle of His / Purkyne fibres ;
[1] D = vein / veins E = artery / arteries F = capillary / capillaries ;
[2] any two from: single layer/ one cell thick ; flattened / thin, cells ; A squamous / pavement, cells / epithelia smooth surface (facing lumen) ;

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.