Alan Zucker, age 72, of Saratoga Springs, N. Y., for his question:
What is the nervous system?
A computer can do some of the things which your nervous system can do. and do them faster; However, no computer has been developed that can do all the things your nervous system can do.
The human nervous system occupies only a small part of the body. Man has not invented a calculating machine or a communicating system to compare with his own neat, compact nervous system.
The nervous system is a well organized set of cells called neurons, Some of the neurons work at central headquarters, which is the brain and spinal cord. Others do the field work of connecting all parts of the body to central headquarters, where decisions are made. The field workers are long, threadlike fibers which carry messages to and fro, much like telephone wires.
A field worker may be a sensory neuron, in which case it can carry messages only from one small part of the body to general headquarters. Or it may be a motor neurons in which case it can carry messages only from headquarters to some part of the body, The field working neurons are usually grouped together in cables varying in thickness from a thread to a pencil. These cables are called the nerves of the body. They are coated with a white protective tissue called myelin.
Each neuron has a small blob of grey matter called the cell body which feeds it and keeps it i n goad repair. It may even repair a damaged thread of a neuron but the cell body cannot repair itself. In a sensory neuron, the cell body is situated along the thread at some distance from headquarters. In a motor neuron it is close enough to connect almost directly with the cells of the brain or spinal cord.
The thread of a neuron may be very long, At the far ends say at the skin of your big toe, it fans out into a set of little branches. The sensitive tips of these branches record events or give orders, depending upon whether the neuron is sensory or motor. A sensory neuron knows when your toe is too hot or too cold. It flashes this information along the nerve cables to headquarters. The brain may decide that you should do something to improve matters about this discomfort. You think of toasting your cold feet by a cozy radiator and the brain gives orders to countless muscles to move your body. These orders are carried by motor neurons,
Sometimes the brain makes fast decisions and takes action before you know it. Suppose you stepped on a hot coal. Sensory nerves flash a message to headquarters and orders come back to leap to safety in a split second. Certain parts of the nervous system work continuously without any help from us. There are nerves which order the stomach to digest its food and they work without consulting us. There are also nerves which keep the heart beating day and do it without consulting our conscious minds.