23ConstructionCircuits

23ConstructionCircuits - Construction of Neural Circuits In...

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Unformatted text preview: Construction of Neural Circuits In order for neurons to properly form synapses, axons must find their way to their appropriate targets. How axons find their way Axonal growth cones Structure Lamellipodia Filopodia Function Explore environment Determine direction of growth Guide extension of axon Figure 23.1 Growth cones guide axons in the developing nervous system (Part 1) Figure 23.1 Growth cones guide axons in the developing nervous system (Part 2) Drawings by Ramon y Cajal of growth cones at different "decision" regions. Green = MT; red = MF Cultured DRG cell Figure 23.2 The structure and action of growth cones (Part 1) actin tyrosinated MT acetylated MT Figure 23.2 The structure and action of growth cones (Part 3) Calcium dynamics Figure 23.2 The structure and action of growth cones (Part 2) Non-diffusible signals for axon guidance ECM molecules and integrins ECM components Laminins Fibronectins Collagens Integrins Receptors for ECM proteins Signal transduction pathways Figure 23.3 The major classes of axon guidance molecules (Part 1) Ca 2+-independent cell adhesion molecules (CAMs) and Ca 2+-dependent cell adhesion molecules (cadherins) Present on growth cones, growing axons and surrounding cells Typically engage in homophilic binding Some assocd w/fasciculation of axons, e.g. L1 CAM Signal transduction is indirect. Figure 23.3 The major classes of axon guidance molecules (Part 2) Figure 23.3 The major classes of axon guidance molecules (Part 3) Figure 23.3 The major classes of axon guidance molecules (Part 6) Diffusible signals for axon guidance Tropism versus Trophism Chemoattractants versus Chemorepellants Figure 23.4 Signals in embryo affect growth cones and growing axons (Part 1) Chemoattractants, e.g. netrins IDd via biochemical purification from chick embryos Product of unc-6 gene ( C. elegans ) Highly homologous to laminin and may i/a w/ECM to influence directed axonal growth Netrin receptors incl. DCC protein Single TMD; no known EZ activity Presumably i/a's w/intracellular signaling proteins w/EZ activity Figure 23.3 The major classes of axon guidance molecules (Part 4) Secreted by cells of floorplate (Unc6) (co-receptor) (Unc40)...
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This note was uploaded on 11/09/2011 for the course CHEM 2341 taught by Professor Staff during the Fall '11 term at Texas State.

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23ConstructionCircuits - Construction of Neural Circuits In...

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