Regeneration of nerves after injury-+

Injury might occur in:

1) Central Nervous System

►Regeneration does not occur

►Permanent loss of function

2) Peripheral nerves

►Regeneration occurs

Injury to nerves is caused by:

►Trauma

►Diseases

►Multiple sclerosis, Diabetes mellitus, polio etc

Regeneration depends upon

►Intact neuronal cell body

►Active Schwann cell

Role of Schwann cells

►Form regeneration tube

►To guide new sprouts of nerve fiber

►Release neurotropic factors (in CNS oligodandrocytes release growth inhibitory factors)

Response of neuron to axonal injury

►Changes in cell body

►Chromatolysis

►Dispersal of Nissl bodies ino cytoplasm

►Nissl bodies become granular

►Cell swells

►Nucleus moves to periphery

►Changes in axon proximal to injury

►Retrograde degeneration

►Fragmentation of axon (up till first node of Ranvier)

►Fragmentation of myelin sheath

►Removal of fragmented parts by macrophages

Changes in axon distal to injury

►Wallerian degenration

►Fragmentation of axon (up till first node of Ranvier)

►Fragmentation of myelin sheath

►Removal of fragmented parts by macrophages