In Chapter 7 on hypertension, the sympathetic nerves are described. These nerves are part of a larger system called the autonomic nervous system. It’s time to describe it.

When you look at the light, the pupil of your eye gets smaller. You don’t have to think about it—it just happens. The same thing happens when you bite a pickle and saliva forms, or when your stomach contracts to propel food along, or when your heartbeat speeds or slows. There are a multitude of functions your body takes care of automatically, through a special set of nerves called the autonomic (automatic) nervous system. There are two parts to this system: the sympathetic and parasympathetic nerves.