exam question & markscheme on control of the cardiac cycle

 

(a)

The cardiac cycle is controlled by the sinoatrial node (SAN) and the atrioventricular node (AVN). Describe how.

(5)

markscheme:

(a) 

1.SAN initiates heartbeat / acts as a pacemaker / myogenic;

Q Must be in context

2.(SAN) sends wave of electrical activity / impulses (across atria)
causing atrial contraction;

Reject: signals / electronic / messages / nerve impulses once only

3.AVN delays (electrical activity / impulses);

Neutral: reference to non-conducting tissue delaying impulses instead of the AVN

4.(Allowing) atria to empty before ventricles contract / ventricles
to fill before they contract;

5.(AVN) sends wave of electrical activity / impulses down
Bundle of His / Purkinje fibres;

6.(Causing) ventricles to contract (from base up) / ventricular
systole;  5 max