11. Without any nervous stimulation, the SA node would establish a sinus rhythm of approximately 100 bpm. 12. In contrast, the SA node in normal state can fire at 60-100 beats per minute. 13. In the absence of extrinsic neural and hormonal control, cells in the SA node will rhythmically discharge. 14. It occurs when the rate of depolarization of the SA node falls below the rate of the AV node. 15. A junctional escape complex is a normal response that may result from excessive vagal tone on the SA node . 16. This can disrupt the electrical pacemaker function of the SA node , and can result in sick sinus syndrome. 17. Normally, all the foci will end up firing at the SA node rate, not their intrinsic rate. 18. Both of these can cause an increased distance of internodal conduction from the SA node to the AV node. 19. Image showing the cardiac pacemaker or SA node , the normal pacemaker within the electrical conduction system of the heart. 20. However, the other firing frequencies are slower than the one of the SA node ( as seen above ).
