(a(i))[1]
Name the principal artery supplying the cardiac muscle from which the SN artery branches.
(a(ii))[2]
With reference to the role of the SAN, suggest how a slow rate of ventricular contraction could show that the SAN is not functioning correctly.
(b)[2]
With reference to the role of the AVN, suggest and explain the change that occurs in heart rate when impulses travel down the bundle of Kent to the ventricles instead of passing through the AVN.