1. Microscopic Structure of the CNS
Ayman Abu-Tabanja, DDS, PhD.

3. Cells of the CNS Two major cell types Nerve cells (Neurons)
2. Neuroglial cells (Glia)

4. Neuron Doctrine (19th Century)
Neuron is a functional & structural unit The indiviuality of neurons NS is Not a syncytium

5. The Neuron

6. Neuronal Types
Based on neurites number
Neurons are classified into:

7. Golgi Classification Golgi type I: large neurons within brain region
2. Golgi type II: small local circuit neurons

8. Neuron cytology
Nucleus
Central
Vesicular
Prominent nucleolus

9. Neuron cytology Cytoplasm Cell body rich in Mitochondria,
Golgi complex, RER
Neurites rich in filamentous organells
microfilaments :
contractile actin
neurofilaments :
structural component
microtubules :
provide a track for transport of proteins

10. Neurites Dendrites: Tapers from cell body Dendritic spines Axon:
Uniform diameter
Missing in some interneurons
Collateral branches
Synaptic terminals

11. Myelin
Interrupted sheath of myelin covers of most of the axon
Laid down by………..
increases the velocity of conduction in nerve fibers

12. Neuronal Synapses

13. Neuronal Synapses Gray’s type I: excitatory Asymmetrical
Gray’s type II:
Inhibitory
Symmetrical

14. Neuronal Synapses: chemical

15. Neuronal Synapses: electrical
Gap junctions
Faster conduction than chemical synapse
Low resistance pathway
Not polarized

16. Neuroglia
Astrocytes
Oligodendrocytes
Microglia
Ependyma

17. Astrocytes Perivascular feet Internal Glial limiting membrane
External Glial limiting membrane
GFAP
Functions:
Supporting framework
Electrical insulators
Supports blood brain barrier
Buffers glutamate and K+
Phagocytic activity

18. Oligodendrocytes Small cell body Conspicuous cytoplasm
Long thin processes rich in
microtubules
Two types:
Interfascicular
Perineural

19. Microglia Smallest glial cells Elongated nuclei
Several short branched processes
Evenly distributed in gray & white matter
Immune effector cells

20. Ependyma single layer Simple cuboidal to columnar epithelium
Lines the ventricular system
Posses microvilli and cilia

21. Ependyma 1. Ependomocytes majority ciliated no tight junctions
Tanycytes
Present in the Floor of 3rd ventricle
Send chemical signal to blood capillaries of hypothalamus

22. Ependyma
3. Choroidal epithelial cells - Cover choroid plexus - Ciliated - Metabolically active - Tight junctions - Forms Blood-CSF barrier

23. Blood brain barrier

25. Circumventricular organs:
- Median eminence
- Pineal body
- Neurohypophesis
- Area postrema
- Subfornical organ
- organum vasculosum of lamina terminalis
Allows sampling of systemic blood for regulation of fluid balance and cardiovascular homeostasis