pathophysiology of nerve
DESCRIPTION
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) - PowerPoint PPT PresentationTRANSCRIPT
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PATHOPHYSIOLOGY OF NERVE
Dr. Ayisha Qureshi Assistant Professor
MBBS, Mphil
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EFFECTS OF CUTTING A MIXED NERVE:
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What will happen if you cut a mixed nerve?
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1. 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.2. 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.4. LOSS OF TROPHIC ACTION: (growth-promoting action)• Atrophy (loss of mass & wasting) of the muscles that were supplied by the motor
nerves.
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DEGENERATION & REGENERATION OF NERVE FIBRES
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DEGENERATION:
• When a nerve fibre is cut or severely crushed, degenerative changes take place at 3 levels:
1.Changes in the nerve cell body2.Changes in the central/proximal stump
(RETROGRADE DEGENERATION)3.Changes in the distal stump
(WALLERIAN DEGENERATION also called the Secondary Degeneration)
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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....
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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.
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REGENERATION:Regeneration of injured nerve fibres will take place in 2 cases:1. If the injury was slight and/ or away from the cell body.2. 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.
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Steps of Regeneration:
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Steps of Regeneration:
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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.
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NO REGENERATION IN CNS:• Regeneration DOES NOT take place in optic nerve
and in the CNS due to the following reasons:1. The endoneural tubes are absent in the CNS as
there are no schwann cells are present; so the regenerating axons cannot be guided.
2. The oligodendrocytes cannot aid in regeneration as the schwann cells.
3. The activity of the astrocytes results in the formation of scar tissue.
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MULTIPLE SCLEROSIS:
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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↓
1. Visual disturbances2. Tingling & numbness
3. Muscle weakness & Fatigue4. Gradual paralysis
5. Bladder & bowel problems
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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