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