There is one important process that every neuron has called an axon, which is the fiber that connects a neuron with its target. Neurons are cells and therefore have a soma, or cell body, but they also have extensions of the cell each extension is generally referred to as a process. To describe the functional divisions of the nervous system, it is important to understand the structure of a neuron. The neuron is the more functionally important of the two, in terms of the communicative function of the nervous system.
A glial cell is one of a variety of cells that provide a framework of tissue that supports the neurons and their activities. Nervous tissue, present in both the CNS and PNS, contains two basic types of cells: neurons and glial cells. The equivalent structures in the CNS are not obvious from this overall perspective and are best examined in prepared tissue under the microscope. The structures of the PNS are referred to as ganglia and nerves, which can be seen as distinct structures. In comparison, it is easy to see that the stomach is different than the esophagus or the liver, so you can imagine the digestive system as a collection of specific organs. It is as if the nervous system is composed of many organs that all look similar and can only be differentiated using tools such as the microscope or electrophysiology. Within the brain, many different and separate regions are responsible for many different and separate functions. That suggests it is made of two organs-and you may not even think of the spinal cord as an organ-but the nervous system is a very complex structure. The picture you have in your mind of the nervous system probably includes the brain, the nervous tissue contained within the cranium, and the spinal cord, the extension of nervous tissue within the vertebral column.
By the end of this section, you will be able to:
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