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 consist of cell body
( perikaryon), dendrite and axon.
Anatomically nervous tissue is subdivided into two portions :
1.Central nervous system (CNS): spinal cord and brain.
2.Peripheral nervous system (PNS):nerve fibers and ganglia.

2. 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 formed by Oligodendrocytes while in PNS formed by Schwann cells.
GANGLIA : A peripheral collection of neurons bodies outside the CNS divided in to craniospinal ganglia and autonomic ganglia

3. 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 non myelinated 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

4. Spinal cord