nervous tissues

? Definition: is highly specialized tissue to employ modifications in membrane electrical potentials to relay signals throughout the body.

? Subdivision of nervous tissues:
1. Anatomical subdivisions:
A. Central nervous system (CNS)
1) Brain
2) Spinal cord
B. Peripheral nervous system (PNS)
1) Nerves
2) Ganglia (singular, ganglion)
2. Structural subdivisions:
A. Nerve cell (neuron):
1) Functional units of the nervous system; receive, process, store, and transmit information to and from other neurons, muscle cells, or glands.
2) Composed of a cell body, dendrites, axon and its terminal arborization, and synapses.
B. Glial cells (neuroglia) (supporting cells):
1) Provide metabolic and structural support for neurons, insulation (myelin sheath), homeostasis, and phagocytic functions
2) Comprised of astrocytes, oligodendrocytes, microglia, and ependymal cells in the CNS; comprised of satellite cells and Schwann cells in the PNS.
? Structure of a Typical Neuron:

1. Cell body (Soma):
a. Nucleus: Large, spherical, usually centrally located in the soma
b. Cytoplasm (perikaryon)
1) Intermediate filaments (neurofilaments), act As a skeleton transportation.
2) rough endoplasmic reticulum (Nissl bodies), which are the site of protein synthesis.