Repair and Regeneration of the Nervous System
What’s Capable of Being Repaired or Regenerated?
• Whole Neurons• Axons• Synaptic clefts
• Neuromuscular junction
• Receptors
Whole NeuronsDeath is programmed (apotosis) or immediated (necrosis)
If you had too much MSG…..
Axons (Peripheral Nerves)
Axons Derive From Growth Cones
How Do Axons Know Where To Go?
• Blueprint Hypothesis– Axons migrate towards a tissue in a pre-
determined manner
• Chemical Affinity Hypotheis– Axons migrate towards a tissue based on
feedback from “chemoattractants” and “chemorepellants”
– Ephrin (retractant), Semaphorins (both)
Signaling Disruption of Axon Growth
Synaptic Clefts (Neuromuscular Junction)
Principles of Neural Science (Kandel); Chapter 55
Formation of a Neuromuscular Junction
• Growth cone approaches a new formed myotube
• Forms an unspecialized contact• Multiple axons converge on a single site• All but one are eliminated
– Survival of the fittest
Principles of Neural Science (Kandel); Chapter 55
What Happens With a Loss of Nerve and Tissue?
Principles of Neural Science (Kandel); Chapter 55
Differentiation of Synaptic vs. Non-synaptic Regions
Principles of Neural Science (Kandel); Chapter 55
Receptor Aggregation
Neuregulin: enables the formation of AcH receptors at the neuromuscular junction
Cytoplasmic Proteins
• link receptors together
Macromolecular Complexes
Principles of Neural Science (Kandel); Chapter 55
• link pre- and post-synaptic membranes together
Neurotrophic Factors
• Guide neuron survival and outgrowth on neurons
• BDNF, NT-3, NT-4 and 5• Hot factor to study beyond
neuron repair and regeneration (drug addiction)
Case Study: Stroke, Chemical Warfare, and Neuregulin
Spinal Cord Regeneration with Channel Rhodopsin
• Achieved through optogenetics
http://www.scientificamerican.com/video.cfm?id=method-of-the-year-2010-12-22