The central nervous system

The central nervous system works in more than one way. There are simple reflex actions and there are reactions at higher levels. Consider, for example, what happens when you unexpectedly touch a hot object. Instantly, your hand is jerked away. The pain stimulated the receptor endings in a sensory nerve in the skin. Nerve impulses immediately flowed along a fiber, passed through a sensory branch of a spinal nerve and into the cord. 

There then followed a quick transfer across a synap of a central nerve in the cord, another transfer across another synapse t a motor nerve, which then passed impulses out of the cord and along a motor fiber of a spinal nerve through the body to the muscles. The muscles reacted; your hand was jerked away. It took just a fraction of a second for the entire reflex-an involuntary process, requiring n thought, assuring immediate helpful action.

 But there was another reaction, too-at higher levels. Although you were not consciously aware of the reflex as it happened, you very quickly learned about it through another transfer in the cord.

The areas sent messages to your muscles, and you moved to the tap. And, as you probably realize, while all this was going on, your emotional centers entered the picture and you had some feelings-perhaps of anger, or disgust, or both-about the event. 

The Autonomic Nervous System A second nervous system, the autonomic, provides for control, on an automatic basis, of vital internal organs. The autonomic system has two nicely balanced parts-the sympathetic and the parasympathetic-which oppose each other, much like accelerator and brake of a car. In so doing, they make possible a precise balance. The sympathetic system begins at the base of the brain and runs along both sides of the spinal column.