Ch. 12.5- Axon regeneration

Question 1

What are the factors that effect axon regeneration?

Answer 1

The amount of damage and the distance between the axon and the tissue it innervates. Increases in either of these two factors decreases the odds of successful healing.

Question 2

What type of glial cell helps with axon regeneration?

Answer 2

Neurolemocytes

Question 3

What are the steps of axon regeneration?

Answer 3

1) Axon is severed by some type of trauma
2) Proximal portion seals off by membrane fusion and swells. Swelling caused from axoplasmic flow. Axon severed from cell body and myelin sheath break down. Macrophages clear out debris, but the neurolemma at the distal end of the axon survives.
3) Neurolemma and remaining endoneurium form a regeneration tube.
4) Axon begins to regeneration and remyelination occurs.
Regeneration tube guides the axon sprout as it grows at 2-5 mm per day. Neurolemmacytes release nerve growth factors that encourage this growth.
5) Innervation is restored as the axon re-establishes functional contact with original structure. This is either a receptor for sensory neurons or an effector for motor control.

Question 4

Wallerian degeneration

Answer 4

When an axon sheath and axon break down after being severed from the cell body.