(a)[3]
Outline the roles of the sinoatrial node (SAN) and the atrioventricular node (AVN) in starting and regulating heart action.
(b(i))[1]
Complete Fig. 5.1 by identifying the type of blood vessel shown by D, E and F.
(b(ii))[2]
The inner lining of the walls of D and E is formed from endothelial tissue. State two structural features of this tissue.