Alya Amila Fitrie , Radita N.A. Ginting, ZulhamAlya Amila Fitrie , Radita N.A. Ginting, ZulhamDepartment of HistologyDepartment of Histology

Medical FacultyMedical FacultyUniversity of Sumatera UtaraUniversity of Sumatera Utara

Nerve Tissue & Nervous System

Topics

1. Histology of Nerve Tissue2. Histology of Central nervous System3. Histology of Peripheral Nervous System4. Nerve Regeneration

HISTOLOGY OF NERVE TISSUE

Cells of Nervous System

Neurons

Cell body

 Ultrastructure of a neuronal cell body. (From Lentz TL: Cell Fine Structure: An Atlas of Drawings of Whole-Cell Structure. Philadelphia, WB Saunders, 1971.)

Main types of neurons

1. Multipolar : most neuron of body

2. Bipolar : cochlear & vestibular ganglia, retina & olfactory mucosa

3. Pseudounipolar : spinal ganglia

Special types of neuron

NeurogliaGlial cells : 10 times abundant than

neurons

Glial cells surround both cell bodies and their processes that occupy the interneuronal space

Oligodendrocytes & Schwann cell•Oligodendrocyte : Produces the myelin sheath that provides the electrical insulation of neurons in CNS

•Schwann Cell : Produce a myelin sheath that located around axons in PNS

Astrocytes

Ependymal cells &Microglia

• Ependymal cells : cuboidal or low columnar epithelial cells, lining the ventricles of the brain and central canal of the spinal cord.

• Microglia : small elongated cells with short irregular processes.

HISTOLOGY OF CENTRAL NERVOUS SYSTEM

Central Nervous System

Cerebrum

Cerebellum

Spinal cord

Cerebrum

Neuron types in the cerebral cortex:1. Pyramidal cells2. Stellate (granul cells)3. Cells of Martinotti4. Fusiform cells5. Horizontal cells of Cajal

Cerebrum (cont..)

Layers

1.Gray Matter / cerebral cortex:

a. Plexiform (molecular) layer

b. Outer granular layer

c. Pyramidal cell layer

d. Inner granular layer

e. Ganglionic layer

f. Multiform cell layer

2.White matter

Cerebellum

Function : coordinates muscular activity and maintain posture & equilibrium.

Consist of :

1. Gray matter :

• Molecular layer

• Purkinje cell layer

• Granular layer

2. White matter

Cerebellum (cont..)

Spinal Cord

Consist of :

1. White matter, in the outer

2. Grey matter, has the shape of butterfly

Meninges

Consists of 3 layer :

1. Dura mater : composed of dense connective tissue, continuous with the periosteum of the skull.

2. Arachnoid : has 2 component :

• A layer in contact to dura mater

• A system of trabeculae

3. Pia mater : loose connective tissue containing many blood vessels

Blood-Brain Barrier

• BBB, a functional barrier, prevents the passage of some substances, from the blood to the nerve tissue.

• Supported by :1. Occluding junction between

endothelial cells of blood capillaries of nerve tissue.

2. The expansion of neuroglial cells processes that envelop the capillaries.

Blood

braIn

Choroid Plexus & Cerebrospinal Fluid

• CP, composed of loose connective tissue of the piamater, covered by simple cuboidal or low columnar epithelium.

• Function of CP is to elaborate CSF, that fills ventricles, central canal of spinal cord, subarachnoid space & perivascular space.

• CSF is clear,low density, & very low in protein content.

Spinal cordSubarachnoid space

Perivascular space

HISTOLOGY OF PERIPHERAL NERVOUS SYSTEM

Peripheral Nervous System

Nerve fibers

Ganglia

Nerve endings

Nerve fibers

Consist of axons enveloped by a special sheath derived from cells of ectodermal origin.

The sheath cell of – PNS Schwann cell – CNS oligodendrocyte

Axon of small diameter unmyelinated nerve fibers

Thicker axons myelinated nerve fibers

Nerve fibers

• E : epineurim• P : perineurium• F : fasiculus• V : blood vessels

Nerve fibers

Nerve fiber

Nerve fibers

Electron microscope of a peripheral nerve containing both myelinated (M) and unmyelinated (U) nerve fibers.

Ultrastructural features of myelinated & unmyelinated nerve

fiber1. Nucleus & cytoplasm of a Schwann

cell

2. Axon

3. Microtubule

4. Neurofilament

5. Myelin sheath

6. Mesaxon

7. Node of Ranvier

8. Interdigitating processes of Schwann cells at the node of Ranvier

9. Side view of an unmyelinated axon

10.Basal lamina

Ganglia

• Ganglia are ovoid structures containing neuronal cell bodies and glial cells supported by connective tissue.

• They serve as relay stations to transmit nerve impulses.

• There are Sensory ganglia & Autonomic ganglia.

Sensory Ganglia Receive afferent impulses that go

to CNS. Two types :

Cranial ganglia : associated with cranial nerves.

Spinal ganglia : associated with the dorsal root of the spinal nerves.

Large neuronal cell bodies with prominent fine Nissl bodies surrounded by abundant small glial cells called satellite cells.

Autonomic Ganglia

• Appear as bulbous dilatation in autonomic nerves.

• Usually have multipolar neurons.• Have neuronal perikaryons with

fine Nissl bodies.• Enveloped by satellite cells.

Autonomic Nervous System

ANS related to the control of smooth muscle, the secretion of some glands & modulation of cardiac rhythm.

ANS are organized & regulated in the CNS. Anatomically, ANS composed of :

collection of nerve cell located in CNS fibers that leave the CNS through cranial or spinal nerves. nerve ganglia situated in the paths of these fibers.

Consist of : Sympathetic & Parasympathetic System

The Nuclei of ANS

• Sympathetic System : collection of nerve cell bodies (nuclei) located in the thoracic & lumbar segments of the spinal cord thoracolumbar division of ANS

• Parasympathetic System : nuclei in the medulla and midbrain & sacral position of the spinal cord craniosacral division of ANS

Nerve Regeneration

Nerve Regeneration

Nerve cell (neuron) : no regeneration if soma or dendrites injured. But, nerve fiber injured : regeneration (+)

Neuroglia of CNS, Schwann cell & ganglionic satellite cells of PNS : able to divide by mitosis regeneration.

Degeneration & regeneration of peripheral nerve