How does the autonomic nervous system work?
The autonomic nervous system is comprised of the sympathetic and parasympathetic nerves. The following example illustrates the interaction between these two nerves:
Prior to our comfortable, modern age, our ancient ancestors had to fight daily for their survival. The body reacts to these stressful situations with increased activity in the sympathetic nerve (tension nerve). Blood pressure becomes elevated, muscles are tightened and sugar (energy), along with stress hormones, is pumped into the blood stream. Simultaneously, systems that do not contribute to the fight or flight mode (digestion or the immune or hormonal systems) are slowed down. The stress hormones released are necessary to maintain the fight or flight condition. As soon as the fight or flight situation has passed, the sympathetic nerve slows down and the parasympathetic nerve (relaxation nerve) is activated in order to begin rejuvenating and regenerating the body.