1. بسم الله الرحمن الرحيم

2. Rawan turky  The neuron (nerve cell) is the structural and functional unit of the nervous system.  Nerve cell size range: 4µ up to 100µ.  Cell membrane very thin  Nucleus vesicular, spherical and central.  No centrioles.  Neurofibril of cytoplasm are parallel  Nissl granules are characteristic to nerve cell  Golgi complex surround nucleus and well developed  Nerve cell inclusion include glycogen, fat droplets, Melanin pigments in addition to lipofuscin granules (yellowish lipochrome granules).

3. Rawan turky

4. Types of Nerve cells Unipolar nerve cell :

5. Pseudo-unipolar nerve:

6. Bipolar nerve cell

7. Multipolar nerve cell

8. Pyramidal cell

9. Types of Nerves Fibers or Axons The axons may be naked or may be covered with: Myelin sheath Neurolemma Both

10. 1. Naked nerve fiber: No myelin sheath and no Neurolemma as fiber in gray matter 2. Myelinated nerve fiber: No Neurolemma as fibers in white matter. 3. Myelinated nerve fiber with Neurolemma as the peripheral somatic nerves outside the spinal cord. 4. Nerve fiber which are covered with Neurolemma but no with myelin sheath as the post ganglionic fibers. Rawan turky

12. Myelin sheath  Cover the axon and formed by neurolemmal cells which surround the peripheral nervs.  In brain is formed by neuroglia or neuroglial cells.  Composed of choesterol, fatty acids and phospholipid  It is interrupted by:  1. Non-myelinated Nodes of Ranvir.  2. Lanterman’s clefts:  Facilitated the passage of molecules from Schwann’s cell to myelin.  To maintain the myelin sheath in a good condition. Rawan turky