Term
|
Definition
| Axons intact but conduction ceases due to local ischaemia and demylination. Spontaeneous recovery. |
|
|
Term
|
Definition
| Axon damaged by compressoin or traction such that the distal portion degenerates. Investing sheaths remain intact and delayed recovery is likely. |
|
|
Term
|
Definition
| The axon is completely divided. Distal portion degenerates and proximal portion can only regenerate if the investing sheaths are repaired. |
|
|
Term
| Describe the process of axon degeneration. |
|
Definition
1) Motor terminal degenerates
2) Wallerian degeneration of distal segment
3) Muscle atrophy
4) Schwannn cells withdraw leaving myelin debris
5) Macrophages enter lesion site and phagocytose the distal axon/ myelin
6) Cell body nucleus displaced. Chromatolysis
7) Synaptic contacts removed. |
|
|
Term
| What is Wallerian degeneration? |
|
Definition
| Myelin sheath unravells and disintegrates coupled with the clumping of axons and neurofilaments . Axon swells and breaks up ino small, beaded segments. |
|
|
Term
| Describe the process of motor axon regeneration. |
|
Definition
1) The motoneurone synthesises proteins needed for axonal growth
2) It sprouts
3) Guided by ECM or schwann cell array
4) When it contacts a muscle retrograde signals influence gene expression to allow it to function as a transmitting neuron again. |
|
|
Term
| What is the difference between myelin produced by oligodendrocytes and schwann cells? |
|
Definition
| Oligodendrocyte myelin contains proteins that inhibit cell growth. |
|
|
