1. NERVOUS TISSUE Forms the nervous system which is divided into:
Central Nervous System (CNS):
Brain
Spinal cord
Peripheral Nervous System (PNS):
Cranial nerves
Spinal nerves
Neurons (nerve cells): The units of nervous tissue. They receive and transmit impulses.
Neuroglial cells: do not receive or transmit impulses; instead, they support neurons.

2. NEURONS
The units of nervous tissue. They receive and transmit nerve impulses to & from the CNS.
A neuron = nerve cell body + all its processes:
One axon.
One or more dendrites.

3. Types of Neurons
Unipolar.
Bipolar.
Multipolar.

4. Unipolar Neurons Formerly called pseudounipolar.
Only one process that divides into a peripheral branch (dendrite) and a central branch (axon).
Present in the dorsal root ganglia of spinal nerves.

5. Bipolar Neurons Two processes: a single dendrite and a single axon.
Present in:
Nasal cavity (olfactory epithelium).
Inner ear.
Retina.

6. Multipolar Neurons The most common type.
Multiple dendrites and a single axon.
Present throughout the nervous system: e.g.
Stellate cells: motor neurons in spinal cord.
Pyramidal cells: in cerebral cortex.
Purkinje cells: in cerebellum.

7. Nerve Cell Body Nucleus: spherical, central with prominent nucleolus.
Cytoplasm:
Abundant rER & polyribosomes.
Prominent Golgi.
Many mitochondria.
Only 1 centriole.
Microtubules, neurofilaments.
Nissl bodies

8. Nerve Cell Processes Dendrites Axon One or more processes.
Single thin long process.
Wide base, tapering tip.
Same diameter in any of its parts.
Give many branches.
Few collateral branches.
Ends by terminal arborizations.
Contain mitochondria, neurofilaments and Nissl bodies.
Contains mitochondria, neurofilaments but no Nissl bodies.
Carry impulse toward cell body.
Carry impulse away from cell body.

9. Nerve Fibers
A nerve fiber = any long process of a nerve cell (axon or dendrite).
Types of nerve fibers:
Myelinated:
Covered by myelin sheath formed by Schwann cells in PNS and oligodendrocytes in CNS.
In white matter of CNS and all peripheral nerves.
Unmyelinated:
Not covered by myelin sheath.
In grey matter of CNS and terminal parts of all peripheral nerve fibers.

10. Peripheral Nerve Trunk
The whole nerve is covered by a C.T. covering, the epineurium.
Consists of parallel myelinated nerve fibers, arranged in bundles, separated by C.T. septa, the perineurium.
The individual nerve fibers are separated by C.T., endoneurium.
Epineurium
Perineurium
Endoneurium

11. NEUROGLIAL CELLS
Supportive and protective to neurons. They do not receive or transmit nerve impulses.
All are present in CNS except Schwann cell (in PNS).
Types:
Astrocytes: nutritive function.
Oligodendrocytes: formation of myelin in CNS.
Microglia: phagocytic (defence).
Schwann cells: formation of myelin in PNS.