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Synaptic Transmission

Synaptic Transmission. Lesson 11. Synaptic Events. Action Potential reaches axon terminal Chemical substance released Neurotransmitter (NT) Diffuses across synapse Binds to receptor protein EPSP or IPSP ~. Synaptic Transmission Model. 1. Precursor transport 2. NT synthesis

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Synaptic Transmission

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  1. Synaptic Transmission Lesson 11

  2. Synaptic Events • Action Potential reaches axon terminal • Chemical substance released • Neurotransmitter (NT) • Diffuses across synapse • Binds to receptor protein • EPSP or IPSP ~

  3. Synaptic Transmission Model 1. Precursor transport 2. NT synthesis 3. Storage 4. Release 5. Activation 6. Termination ~

  4. Postsynaptic Membrane Presynaptic Axon Terminal Dendritic Spine Terminal Button

  5. 1. Precursor Transport

  6. 1. Precursor Transport

  7. 2. Synthesis Enzymes & cofactors ~ E

  8. 3. Storage E

  9. 3. Storage In vesicles Terminal Button Dendritic Spine Synapse

  10. Ca++ 4. Release • via exocytosis • diffusion

  11. AP Ca++ 4. Release • via exocytosis • diffusion Synapse

  12. Ca++ 4. Release • via exocytosis • diffusion

  13. Exocytosis: Membrane Fusion • Ca2+ influx • Ca2+ -Calmodulin • synapsin • SNAPs • soluble-NSF-attachment proteins • Cell membrane • SNAREs • SNAP receptors • Vesicle & cell membrane~

  14. 5. Activation • NT binds to receptor

  15. Activation • NT binds to postsynaptic receptor • opens ion channel • EPSP • Na+ into cell • or IPSP • K+ out of cell ~

  16. 6. Termination • 4 basic methods

  17. 6. Termination • diffusion

  18. 6. Termination • Enzymatic degradation

  19. 6. Termination • Presynaptic reuptake • active transport

  20. 6. Termination • autoreceptors A

  21. Autoreceptors • On presynaptic terminal • Binds NT • same as postsynaptic receptors • different receptor subtype • Decreases NT release & synthesis ~

  22. Termination • Must have discrete signal • What if ion channels continually open? • ions move toward equilibrium • membrane no longer polarized • no EPSPs or IPSPs • Disrupts neural communication • Termination  neuron repolarizes ~

  23. Axoaxonic Synapses • Modulation of NT release • Presynaptic Facilitation • Increases NT release • Presynaptic Inhibition • decreases NT release • Via modulation of Em • Ca2+, K+, and Cl- ~

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