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. Depending on different aspects of the nervous system, the dividing line between central and peripheral is not necessarily universal.įigure 12.2 Central and Peripheral Nervous System The structures of the PNS are referred to as ganglia and nerves, which can be seen as distinct structures. The peripheral nervous system is so named because it is on the periphery-meaning beyond the brain and spinal cord. In actuality, there are some elements of the peripheral nervous system that are within the cranial or vertebral cavities. It is a bit of an oversimplification to say that the CNS is what is inside these two cavities and the peripheral nervous system is outside of them, but that is one way to start to think about it. The brain is contained within the cranial cavity of the skull, and the spinal cord is contained within the vertebral cavity of the vertebral column. The central nervous system (CNS) is the brain and spinal cord, and the peripheral nervous system (PNS) is everything else ( Figure 12.2). The nervous system can be divided into two major regions: the central and peripheral nervous systems. The Central and Peripheral Nervous Systems 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. List the basic functions of the nervous system.Relate the functional and structural differences between gray matter and white matter structures of the nervous system to the structure of neurons.Identify the anatomical and functional divisions of the nervous system.By the end of this section, you will be able to:
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