CONTROL OF CARDIAC ACTIVITY BY THE NERVOUS SYSTEM

The main functions of the heart are regulated by the sympathetic and parasympathetic divisions of the autonomic nervous system. In general, the sympathetic nerves of the heart are facilitatory, while the parasympathetic (vagus) nerves are inhibitory. The kinetics of the two autonomous cleavages are significantly different. Vagal effects develop very quickly, often within a heartbeat, and they also decay quickly. Thus, the vagus nerve has the ability to control the activity of the heart. On the contrary, the onset and decay of sympathetic influences is much more gradual; only small changes are made during one cardiac cycle. When two autonomous systems act simultaneously, the effects are not algebraically additive, but complex interactions prevail.