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Neuron structure

Neuron structure. Structure: How does the neuron maintain its complex extended shape? Transport: How are materials transported long distances from the cell soma? Growth & plasticity: How does a neuron acquire and modify its shape ?. The neuronal cytoskeleton Cytoskeletal components.

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Neuron structure

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  1. Neuron structure • Structure: How does the neuron maintain its complex extended shape? • Transport: How are materials transported long distances from the cell soma? • Growth & plasticity: How does a neuron acquire and modify its shape ?

  2. The neuronal cytoskeleton Cytoskeletal components • Structure: focus on neurofilaments (axons) and microtubules • Transport: focus on microtubules •Growth & plasticity: • focus on actin

  3. Intermediate filaments

  4. Neurofilaments

  5. Crosslinking provides strength and stiffness

  6. Neurofilament are crosslinked in axons • Crosslinked NFs provide • strength and stiffness, • especially important in • long axons. • NFs are highly enriched in • axons and are the principal • structural support in • axons. Increasing the • number of NFs increases • the diameter of the axon • (and consequently its • conduction velocity).

  7. Microtubules

  8. Microtubule polymerization & depolymerization

  9. Microtubulle-associated proteins (MAPs) • Assembly MAPs • Tublin-binding end facilitates assembly and stabilizes MT • Projection end crosslinks MTs to neuro-filaments to membranes or to other MTs

  10. Microtubulle-associated proteins (MAPs) • MAP Bridges • arrows show bridges between microtubules star shows bridge between microtubule and vesicle • Crosslinked microtubules • add structural stability to • axons and, especially, to • dendrites.

  11. Microtubulle-associated proteins (MAPs • Motor MAPs • • Tubulin-binding end is an • ATP-dependent motor that moves • along length of MT. • • kinesins toward plus end • • dyneins toward minus end • • projection end links MTs to • “cargos”: mainly different types • of membrane-enclosed organelles • (e.g., mitochondria, vesicles)

  12. Axonall Transport • • Most protein synthesis occurs in the soma or • dendrites. How are the axon & axon terminals • supplied with new proteins and organelles? • • Contact with other neurons occurs at the synapses. • How does information get back to the soma • regarding the experience of the synapse?

  13. Transport iin neurons In axons, all MTs are oriented so that the plus ends are distal (away from cell body). In dendrites, MTs are randomly oriented.

  14. terminal Soma axon – + + – + – + + – K – D • In axons, kinesin moves vesicles towards • the terminal (distal); dynein moves • vesicles toward the cell soma (proximal). – + – + polarized microtubules (+ ends distal )

  15. Fast anterograde axonal transport (≈300 μm/m, ≈400 • mm/day) • • mainly organelles, vesicles • • kinesin-based movement of cargos • • Fast retrograde axonal transport • • mainly vesicles carrying signaling molecules from the • axon terminals to the cell body • • dynein-based movement of cargos • • Slow axonal transport (≈7 μm/m, ≈10 mm/day) • •actin, soluble metabolic enzymes (glycolysis, • neurotransmitter synthesis) • • MTs, actin motility • • Slowest axonal transport (0.2-2 μm/m, 0.5-3 mm/day) • • Microtubules, neurofilaments

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