CSB332H1 Lecture Notes - Lecture 10: Wallerian Degeneration, Reinnervation, Myocyte
9 Aug 2012
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Most often synapse becomes weakened: either due to decrease in amt of transmitter released or in the density of postsynaptic recs. Retrograde signals cause many presynaptic terminals to retract. If neuron regenerates & re-innervates target synaptic inputs recover. The neuron synapsing onto the motoneuron & its target are also affected. Wallerian degeneration: characteristic seq of events following severing of a vertebrate peripheral nerve. Injury/lesion distal axon degenerates: schwann cells (had formed myelin sheath) dedifferentiate, proliferate, and w invading macrophages & microglia from blood, phagocytize the axonal & myelin debris. Recycle nutrients: cell body & nucleus of injured neuron swell. Several hrs later: axon sprouts near proximal region & begins to regenerate, schwann cells preserve endoneural tube so axon can grow back thru. If a connection is reestablished cell body resumes its normal position: axon regenerates along the column of schwann cells. If a connection not reestablished cell often dies rapidly.
