Nervous tissue is composed of two types of cells: 1. Neurons ¾ transmit nerve impulses. 2. Neuroglial cells (glial cells)

Nervous tissue is composed of two types of cells: 1. Neurons ¾ transmit nerve impulses. 2. Neuroglial cells (glial cells) ¾ are non-conducting “support cells” of nervous tissue. Examples include astrocytes, attached to the outside of a capillary blood vessel in the brain, phagocytic microglial cells, and ciliated ependymal cells that form a sheath that usually lines fluid cavities in the brain. Structure of a neuron: • Cell body (perikaryon) ¾ contains the nucleus and most of the cytoplasm. Located mostly in the central nervous system as clusters called nuclei, some found in the peripheral nervous system as groups called ganglia. • Dendrites ¾ neuronal processes that send the impulse toward the cell body. There may be one or many dendrites per cell. Some neurons lack dendrites. • Axon (nerve fiber) ¾ neuronal process that sends the impulse away from the cell body. *** If the axon is covered with a fatty substance called myelin, the axon is referred to as a myelinated fiber. If there is no myelinated cover, then the axon is referred to as an unmyelinated fiber. Neurons are classified according to structure (based on the number of processes that extend from the cell body): bipolar, unipolar, or multipolar (most common). They are also classified according to function: motor (efferent), sensory (afferent), or interneurons (which lie between sensory and motor neurons in the CNS). Note: Whether or not someone feels different stimuli (pain, temperature, pressure, etc.) is determined by the specific nerve fiber s