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PATHOPHYSIOLOGY OF NERVE

PATHOPHYSIOLOGY OF NERVE. Dr. Ayisha Qureshi Assistant Professor MBBS, Mphil. Effects of cutting a mixed nerve: . What will happen if you cut a mixed nerve?. LOSS OF MOTOR ACTIVITY: Affected muscles become paralyzed & show reflex activity Muscles become flaccid (NO TONE)

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PATHOPHYSIOLOGY OF NERVE

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  1. PATHOPHYSIOLOGY OF NERVE Dr. AyishaQureshi Assistant Professor MBBS, Mphil

  2. Effects of cutting a mixed nerve:

  3. What will happen if you cut a mixed nerve?

  4. LOSS OF MOTOR ACTIVITY: • Affected muscles become paralyzed & show reflex activity • Muscles become flaccid (NO TONE) • Rapidly undergo loss of mass (WASTING) • Muscles start showing the ERB’S REACTION OF DEGENERATION: altered response of the muscles to electrical stimulation seen after loss of motor supply. • LOSS OF SENSATIONS: • NO sensation in the area of the cut sensory nerves.. 3. LOSS OF AUTONOMIC NERVE ACTIVITY: • Area becomes blue & cold. • Activity of the sweat glands comes to an end. • LOSS OF TROPHIC ACTION: (growth-promoting action) • Atrophy (loss of mass & wasting) of the muscles that were supplied by the motor nerves.

  5. Degeneration & regeneration of nerve fibres

  6. DEGENERATION: • When a nerve fibre is cut or severely crushed, degenerative changes take place at 3 levels: • Changes in the nerve cell body • Changes in the central/proximal stump (RETROGRADE DEGENERATION) • Changes in the distal stump (WALLERIAN DEGENERATION also called the Secondary Degeneration)

  7. 1. Changes in the nerve cell body: • Cell body swells • Nissl granules undergo dissolution (CHROMATOLYSIS) • Nucleus is pushed to one side • Mitochondria, Golgi apparatus, ribosomes & lysosomes show structural changes • If the axon is cut quiet close to the cell body, the neuron may die....

  8. 2. RETROGRADE DEGENERATION • This is the degeneration that occurs in the central or proximal segment. • Degenerated area may extend upwards for one or more nodes. • Degeneration my be followed by repair...... As this part is still attached to the cell body.

  9. REGENERATION: Regeneration of injured nerve fibres will take place in 2 cases: • If the injury was slight and/ or away from the cell body. • If the injured nerve fibre was part of the PNS. WHAT HAPPENS: • The nissl granules reappear & the nucleus resumes its central position. • Full recovery may take upto 3-6 months. • The endoneural tube is formed by the Schwann cells themselves. This tube guides the regenerating nerve fibre to its proper destination. • At the beginning of the process, axon in the central end of the cut nerve fibers elongate & give rise to large no. Of fibrils that enter into the endoneural tube.

  10. Steps of Regeneration:

  11. Steps of Regeneration:

  12. What is a Neuroma? If the gap between the 2 ends of a crushed nerve fibre is more than 3 mm, the nerve fibres tend to intermesh and form a tumor like swelling called Neuroma. This is very painful in the case of sensory nerves.

  13. NO REGENERATION IN CNS: • Regeneration DOES NOT take place in optic nerve and in the CNS due to the following reasons: • The endoneural tubes are absent in the CNS as there are no schwann cells are present; so the regenerating axons cannot be guided. • The oligodendrocytes cannot aid in regeneration as the schwann cells. • The activity of the astrocytes results in the formation of scar tissue.

  14. MULTIPLE SCLEROSIS:

  15. Multiple Sclerosis: Going, Going, Gone….. It is an auto-immune disease in which there is patchy loss of myelin sheath of nerve fibers leading to disruption of nerve impulse conduction. Cause: Antibodies mistakenly attack and destroy Schwann cells, thus also destroying the myelin sheath. Signs & symptoms: Patchy destruction of myelin in the CNS→ slow & abnormal conduction of the nerve impulses in the neurons ↓ • Visual disturbances • Tingling & numbness • Muscle weakness & Fatigue • Gradual paralysis • Bladder & bowel problems

  16. Treatment • Debilitating disease but not fatal. The quality of life is affected…. Death may occur when the paralysis reaches the respiratory muscles and the person cannot breathe. • No treatment as yet. • Only symptomatic treatment. • Immunosuppressive therapy: as autoimmune disease so you try to suppress the immune system to prevent further damage. • Corticosteroids • Alternative therapy: as homeopathy, ayurvedic treatment etc

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