![Degeneration and regeneration of neurons
Distal nerve segment
Wallerian degeneration
Macrophages remove degenerating axons,myelin and cellular
debris
Loss of axonal continuity is followed by intense proliferation
of schwann cells ,with cells lining up in columns[band of
Bungner]](https://image.slidesharecdn.com/nerveregfinal-170526060141/85/Nerve-reg-final-21-320.jpg)
Nerve reg final
- 1. NERVE REGENERATION Sai lakshmi L.J I yr PG student Oral and maxillofacial pathology
- 2. Agenda Development, Anatomy and Histology Physiology Diseases Genetic Injury Degenerative
- 4. Development of Nervous system Thickening of the ectoderm leads to the development of the neural plate The neural groove begins to develop at 20 days. Just another WordPress.com site
- 5. At 22 days the neural groove closes along the length of the embryo making a tube. Neural tube becomes the central nervous system The neural crest cells become the peripheral nervous system
- 6. Different types of nerves Cranial nerves Spinal nerves
- 7. Structure of neuron Cell body Dendrites Axon Nissl substance Neurofilaments Gray,s anatomy ,14th edition
- 8. Structural classification of Neurons
- 9. Functional Classification of Neurons Based on the direction of conduction Sensory or afferent conduct toward the CNS Motor or efferent conduct away from the CNS Interneuron interposed between sensory and motor neuron
- 10. Glial cells Supporting cells present with in the brain and spinal cord. CNS neuroglia Astrocytes oligodendrocytes microglia ependymal cells PNS neuroglia Schwann cells satellite cells Gray's anatomy ,14th edition
- 11. Oligodendrocytes myelin formation around axons in the CNS Astrocytes Star like shape Nutritive in function Blood brain barrier http://neuromedia.neurobio.ucla.edu/campbell/ http://neuromedia.neurobio.ucla.edu/campbell/
- 12. Ependymal cells Line cavities of the brain and spinal cord Circulate cerebrospinal fluid Microglia “brain macrophages” phagocytize cellular wastes &pathogens School of Anatomy and Human Biology - The University of Western Australia Gray's anatomy ,14th edition
- 13. PNS neuroglia Schwann cells Form myelin sheath in the peripheral nervous system Satellite cells Surround neuron cell bodies. Provide support and nutrients.
- 14. Peripheral nervous system It includes the peripheral nerves and nerve cell bodies outside the CNS Connective tissue investment endoneurium perineurium epineurium Gray's anatomy ,14th edition
- 15. Functions of Neuron Excitability – capable of generating electrical impulses. Conductivity – ability of propagating the electrical impulses. NERVE IMPULSE The plasma membrane at rest is polarized Fewer positive ions are inside the cell than outside the cell
- 16. Stimulus initiates depolarization by allowing sodium (Na+) to flow inside the membrane. The exchange of ions initiates an action potential in the neuron If the action potential (nerve impulse) starts, it is propagated over the entire axon
- 17. Potassium ions rush out of the neuron after sodium ions rush in, which repolarizes the membrane The sodium-potassium pump restores the original configuration This action requires ATP The impulse continues to move toward the cell body Impulses travel faster when fibers have a myelin sheath.
- 18. Nerve Fiber Types Type A fibers Myelinated . Diameter 12 - 20 micro meter. conduction velocity 70 - 120 m/sec . Type B Myelinated, diameter < 3 micro meter. conduction velocity 4- 30 m/sec. Preganglionic autonomic efferent fibres,afferent fibres from skin and viscera. Type C Unmyelinated,diameter 0.4 – 1.2 micro meter. conduction at 0.5 – 4 m/sec . Post ganglionic autonomic fibres ,sensory fibres carrying pain sensation.
- 19. Classification of nerve injuries Based on seddon classification Neuropraxia Local conduction block Local myelin damage with preserved axonal continuity No degeneration Reversible with weeks or months
- 20. Axonotmesis Axon is divided but endoneural sheath is continuous Regeneration is possible . Recovery is complete Neurotmesis Rupture or transection of entire nerve trunk Surgical repair required
- 21. Degeneration and regeneration of neurons Distal nerve segment Wallerian degeneration Macrophages remove degenerating axons,myelin and cellular debris Loss of axonal continuity is followed by intense proliferation of schwann cells ,with cells lining up in columns[band of Bungner]
- 22. Proximal nerve segment Cell body – chromatolysis Increase in cell body volume Displacement of the nucleus to the periphery Changes in structure of the cytoplasm Sprouting Axonal sprouts will grow from the proximal nerve stump across the zone of injury toward the distal segment.
- 23. Progress in neurobiology vol92,issue 3,nov 2010
- 24. Diseases of peripheral nerves CLASSIFICATION GENETIC NEUROPATHY INFLAMMATORY NEUROPATHY INFECTIOUS POLYNEUROPATHIES METABOLIC AND NUTRITIONAL PERIPHERAL NEUROPATHIES TRAUMATIC NEUROPATHIES
- 25. Genetic Neuropathy Hereditary motor and sensory neuropathy Type I Charcot -Marie –Tooth (CMT ) disease Demyelinating type Mutation in gene PMP22 Peroneal muscular atrophy
- 26. consequences of repetitive demyelination and remyelination, with multiple onion bulbs, more pronounced in distal nerves than in proximal nerves
- 27. Inflammatory neuropathy GBS (Guillian Barre syndrome) Immune-Mediated demyelinating Neuropathy weakness beginning in the distal limbs but rapidly advancing to affect proximal muscle function ("ascending paralysis") Histologically by inflammation and demyelination of spinal nerve roots and peripheral nerves . Acute, influenza-like illness followed by neuropathy C jejuni, CMV, EBV & M. pneumoniae associated
- 28. Infectious polyneuropathies Leprosy: Schwann cells are invaded by Mycobacterium leprae, which proliferate & eventually infect other cells. segmental demyelination and remyelination. Diphtheria: Effects of the diphtheria exotoxin & begins with paresthesias and weakness
- 29. Varicella-zoster: • reactivation leads to a painful, vesicular skin eruption in the distribution of sensory dermatomes (shingles), most frequently thoracic or trigeminal.
- 30. Metabolic and Nutritional peripheral Neuropathies • Most individuals with renal failure have a peripheral neuropathy (uremic neuropathy). • Thiamine deficiency, vitamins B12 (cobalamin),B6 (pyridoxine), and E (α-tocopherol ,is associated with axonal neuropathy. • Excessive chronic consumption of ethyl alcohol often leads to axonal neuropathy
- 31. Diabetic neuropathy Marked loss of myelinated fibers & thickening of endoneurial vessel wall. Symmetric neuropathy: involves distal sensory & motor nerves
- 32. • Decreased sensation in the distal extremities • The loss of pain sensation can result in the development of ulcers, which heal poorly because of the diffuse vascular injury in diabetes. Painless nature of diabetic foot disease Slides current until 2008
- 33. Compression neuropathy Carpal tunnel syndrome Results from compression of the median nerve at the level of the wrist Tissue edema, inflammatory arthritis, hypothyroidism, diabetes mellitus. Numbness and paresthesias of the tips of the thumb & first two digits.
- 34. Other nerves prone : ulnar nerve at the level of the elbow, the peroneal nerve at the level of the knee, and radial nerve in the upper arm
- 35. Traumatic Neuroma Reactive proliferation of neural tissue after transection or other damage to nerve bundle. Most common in mental foramen area, tongue and lower lip with a history of trauma Intraosseous lesions appear as radiolucencies.
- 36. Histology: Haphazard proliferation of mature, myelinated nerve bundles within a fibrous connective tissue Treatment: Surgical excision
- 37. References David H cormack ,Ham’s histology, eighth edition Gray’s Anatomy, Anatomical basis of clinical practice, fourtieth edition Ganong’s , Review of Medical Physiology, 24 edition Robbins and cotran ,pathologic basis of disease, eighth edition. Oral & maxillofacial pathology – Neville Allen Damn Bouquot 3rd edition Ronald Deumens,Ahmet Bozkurt, Repairing injured peripheral nerves: Bridging the gap, Progress in Neurobiology, Volume 92, Issue 3, November 2010, Pages 245–276.