system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
S.A. node acts as a pacemaker of the hea because of the fact that it
assistant
The correct answer is  Some cardiac fibers have the capability of self-excitation, a process that can cause automatic rhythmical discharge and contraction. This capability is especially true of the fibers of the hea 's specialized conducting system, including the fibers of the sinus node. For this reason, the sinus node ordinarily controls the rate of beat of the entire heaRef: Guyton and Hall textbook of medical physiology 13th edition. Page: 123