Ass. Lec. Rafah Saleem
Nervous Tissue (system) :
The mammalian nervous system is the most complex system in the
body. It is divided into two major parts :the central nervous system(CN)
w hich consist of the brain and spinal cord ,which are surrounded and
protected by the cranium and vertebral bones . And peripheral nervous
system (PNS),which is located outside of the CNS and composed of
(cranial, spinal ,and peripheral nerve fibers) .
Neurons:
The nervous system is composed of highly complex intercommunicating
networks of nerve cells that receive conduct impulses along their neural
pathways or axons to the CNS .And it is the anatomic and functional
units ,consist of three parts :1.Dendrites : multiple elongated processes specialized in receiving
stimuli from the environment .
2.Cell body : or soma contains the nucleus ,nucleolus,numerous
different organelles and the cytoplasm.
3.The axon : single process specialized in generating or conducting nerve
impulses to other cells.
Neurons are classified on the basis of the number of processes
extending from the cell body to :a. Multipolar ,neurons have an axon and two or more dendrites.
b. Bipolar ,neurons have one axon and one dendrites .
c. Unipolar ,(pseudouipolar) have one process the axon ,that divides
close to cell body to two long processes .
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Ass. Lec. Rafah Saleem
Spinal cord:
In cross section , the spinal cord is organized in to two discrete parts a
butterfly –shaped grayish-tan inner substance ,the gray matter
surrounding the central canal, and a whitish peripheral substance ,the
white matter which contains only myelinated and unmyyelinated axons
traveling to and from other parts of the spinal cord and to from the
brain. The gray matter contains neuronal cell bodies and their dendrites ,
along with axons and neuroglia .
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Ass. Lec. Rafah Saleem
Cerebellum cortex :- consist of :
1. Outer moleculer layer : the nerve cells or neurons have a very
small perikaryone (cell body) and also contain unmyelinated
fibers.
2. Inner granular layer : prominent nuclei of the granular cell .
3. Single layer of Purkinje cells interposed between them .
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Ass. Lec. Rafah Saleem
Gl: granular cell ,Ml:molecular layer ,Pc: purkinge cell
PM:pia matter
CEREBRUM Cortex
The cerebral cortex is composed of gray matter, mostly
subdivided into six layers:1.
2.
3.
4.
5.
6.
Molecular Layer: Composed of horizontal cells and cell processes
External Granular Layer: Consists mostly of granule (stellate) cells, tightly
packed.
External Pyramidal Layer: Large pyramidal cells and granule (stellate) cells.
Internal Granular Layer: Closely packed granule (stellate) cells
Internal Pyramidal Layer: Medium and large pyramidal cells
Multiform Layer: Consisting of various cell shapes, many of which are fusiform.
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Ass. Lec. Rafah Saleem
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