A    Sensory receptor
B    Cardio-inhibitor center
C    Cardio-accelerator center
D    Sensory nerve
E    Parasympatheic (inhibitor) nerve
F    Sympathetic (accelerator) nerve
1    Carotid sinus
2    Carotid artery
3    Aortic arch
4    Superior vena cava
5    Sino-atrial (SA) node (pacemaker)
6    Right atrium
7    Right ventrcle
8    Purkinje fibers
9    Left atrium
10    Atrioventricular (AV) node
11    Bundle of His
12    Left ventricule
13    Interventricular septum
14    Medulla oblongata
15    Sympathetic ganglion
16    Spinal cord