What ultimately happens to the distal end of axons that are cut?

Question

I understand the concept of wallerian degeneration (segmentation of axons after a lesion), but if I cut an axon near its terminal, how long will it take for that terminal and axon (distal to the lesion) to "go away"? ...or will something else happen?

Answer 1

Hey,

I think your idea of wallerian degeneration is wrong; in wallerian degenration, what happens is that an injury occurs to the axon, and the parts of the axon distal to the injury degenerate, basically the axon is fragmented, and macrophages and schwann cells phagocytose the myelin and cell debris.

If the axon was a peripheral axon then most likely it will regenerate with the help of the schwann cells as long as the schwann cells and the cell body is intact. Axons in the CNS tend not to regenerate because of inhibiting growth factor.

Regeneration: The schwann cells divide mitotically and release growth factors such as nerve growth factor and insulin like growth factor. The axon grows in the same way that it grows during embryological development i.e. it forms a growth cone that regenerates towards the targets and original contacts. Cell body synthesizes proteins to aid in growth. It 2 days after injury growth begins and takes a few days to complete i think. Regeneration is not complete.

If the cell body is too damaged or if schwann cells are not present, the axon is disintegrated due to lack of nutrients and die. They are then phagocytosed by macrophages.

I hope ive answered your Q..if not let me know!

Answer 2

It is degraded, how rapidly depends on a number of factors.