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Understanding Synaptic Transmission: Events and Mechanisms

Explore the process of synaptic transmission from action potential to neurotransmitter release, activation, and termination. Learn the key steps and components involved in transmitting signals in the nervous system.

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Understanding Synaptic Transmission: Events and Mechanisms

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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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