2. Structure of neuron and classification

3. Histology of Nervous Tissue
Two principal cell types
Neurons—excitable cells that transmit electrical signals

4. Histology of Nervous Tissue
Neuroglia (glial cells)—supporting cells:
These are non excitable cells which support neurons.
Smaller
More in number

5. Astrocytes (CNS)
Microglia (CNS)
Ependymal cells (CNS)
Oligodendrocytes (CNS)
Satellite cells (PNS)
Schwann cells (PNS

6. Astrocytes fibrous Most abundant, found in white matter
Cling to neurons, synaptic endings, and capillaries
Support and brace neurons
Not much branched

7. Protoplasmic Astrocytes
Found in gray matter
Short thick processes
Inner and outer glial limiting membrane

8. Help determine capillary permeability
Guide migration of young neurons in embryo
Serve as insulators and prevent axon terminals from influencing neighbouringneurons
Control the chemical environment by taking up excess k
Participate in replacement gliois

9. Finally, astrocytes are in direct communication with one another via gap junctions, forming a network through which information can flow from one point to another, reaching distant sites. For example, by means of gap junctions and the release of various cytokines, astrocytes can interact with oligodendrocytes to influence myelin turnover in both normal and abnormal conditions

11. Microglia Small, ovoid cells with thorny processes
Migrate toward injured neurons
Phagocytize microorganisms and neuronal debris
Resemble tissue macrophages

12. Satellite Cells and Schwann Cells
Surround neuron cell bodies in the PNS
Schwann cells (neurolemmocytes)
Surround peripheral nerve fibers and form myelin sheaths
Vital to regeneration of damaged peripheral nerve fibers

13. Satellite
cells
Cell body of neuron
Schwann cells
(forming myelin sheath)
Nerve fiber

14. Oligodendrocytes have processes that form myelin sheaths around CNS nerve fibers.
Process of
oligodendrocyte

16. Structural Classification of Neurons
A. Number, length and mode of branching
Three types:
Multipolar—1 axon and several dendrites
Most abundant
Motor neurons and interneurons
Bipolar—1 axon and 1 dendrite
Rare, e.g., retinal neurons

18. Structural Classification of Neurons
Unipolar (pseudounipolar)—single, short process that has two branches:
Peripheral process—more distal branch, often associated with a sensory receptor
Central process—branch entering the CNS

21. B.SIZE OF NEURON
GOLGI TYPE 1 –Single long axon
Tracts and motor cells of spinal cord,
GOLGI TYPE 11-short axon with dendrites resembles star
Cerebral and cerebellar cortex

22. Functional Classification of Neurons
Three types:
Sensory (afferent)
Transmit impulses from sensory receptors toward the CNS
Motor (efferent)
Carry impulses from the CNS to effectors