Key Features of the Nervous System
Parts: Central Nervous System (CNS) and Peripheral Nervous System (PNS) OR
Somatic Nervous System (SNS) and Autonomic Nervous System (ANS)
Major Tissue Type: Nervous Tissue
Characteristic Cell Types: Neurons, Astrocytes, Microglia, Oligodendrocytes, Schwann Cells, Ependymal cells
Functional Unit: Neuron
Just a word of warning before we begin: The nervous system is the hardest lecture in this course. Studying this topic requires "attention to detail" and "lots of repetition". However, I found this information to be so interesting when I was an undergraduate that it's my specialty--I'm a neuroanatomist/neurophysiologist type who could spend the entire course on this one topic. :)
Let's review two definitions from your reading assignment as we begin this lecture--central nervous systerm or CNS and peripheral nervous system or PNS. The CNS consists of the brain and spinal cord. Remember that both of these structures occupy the dorsal body cavity. The brain sits in the cranial cavity; the spinal cord in the vertebral canal. Nerves seen on the external surface of the brain and spinal cord comprise the PNS along with groups of neurons called ganglia. Ganglia may be sensory or motor. Sensory ganglia contain neuron cell bodies that are responsive to touch, pressure, pain, and temperature, for example. Motor ganglia contain cell bodies that synapse with visceral organs and glands as part of the autonomic nervous system.
The nervous system can also be divided into the somatic nervous system and the autonomic nervous system. This functional scheme separates CNS nuclei and tracts plus PNS nerves and ganglia that supply somatic, "body wall" structures from CNS nuclei and tracts plus PNS nerves and ganglia that supply autonomic, "body cavity" structures.
| Part of Nervous System | Groups of Axons | Groups of Neuron Cell Bodies |
| PNS | Nerves | Ganglia |
| CNS | Tracts | Nuclei |
Connective tissue membranes surround both the CNS and PNS. In the CNS, these coverings are called:
Real and potential spaces occur between these layers. The detail of these spaces, and the characteristics of these membranes differs for the coverings surrounding the brain versus the spinal cord. Based on your knowledge of the definitions of prefixes and suffixes, can you guess the names of these spaces?
In the PNS, the coverings are called:
Lecture 7 is divided into 5 major topics.