1. Nervous tissue
Nervous tissue; basically an integrated communications network distributed throughout the entire body, the main component of this tissue is the neuron, which transmits the impulses, in addition to the neuron, glial cell (neuroglia).
The neuron: it is functional unit of CN consisted from
1. Cell body ;( perikaryon) has variable shapes containing large central nucleus, their cytoplasm characterized by presence the nissl bodies.
2. Dendrite; consisted from multiple elongated cellular processes, it can be numerous and highly branched.
3. Axon; is the cylindrical, long cellular process that variable in length,
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2. Dr.dhyaa

3. Classification of neurons
Histological and according to the configuration of their processes.
Mutipolar neurons (have 2 or more dendrite and 1 axon).
Bipolar neurons (have single dendrite and one axon).
Pseudo uni polar neurons (begin in the embryo as bipolar cells later fused to form a single T-shaped process.
Uni-polar-neuron (have single short axon and no dendrite)
(rods cones).
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4. Peripheral nervous system
Nervous tissue within the PNS consist of bundles of nerve fibers (nerves) that are myelinated which involved the cranial and spinal nerves
Nerve fibers;
The axon may enveloped by special sheaths( myelin sheaths) provided by support cells, these sheaths protected axon and help in conducting impulses, so the axon enveloped with sheaths called myelinated while the not enveloped called non myelinated. In CNS this sheaths are called Oligodendrocytes while in PNS they are called Schwann cells.
The region where two adjacent myelin ensheathments meet called node of Ranvier (non sheathed area)
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5. CENTRAL NERVOUS SYSTEM
brain (cerebellum, cerebrum, and brain stem)
Spinal cord.
Both anatomically and histologically divided into major component gray mater and white mater.
GRAY MATER
Largely consist of perikaryon and small amount of nerve fibers that may be myelinated. In brain, the gray matter is peripherally located forming the cortex of the cerebrum and cerebellum. While in spinal cord the gray matter centrally located.
WHITE MATER
In generally its absence of perikaryon and its prevalence of myelinated axon and some of numyelinated nerve fibers.
MENINGES are fibrous tissue surrounded and
protected the brain and spinal cord divided into
cranial and spinal meninges involved:
Pia mater.
Archnoid .
Dura mater
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