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Synaptic Transmission

Synaptic Transmission. 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. Precursor transport NT synthesis Storage Release

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Synaptic Transmission

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  1. Synaptic Transmission

  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 • Precursor transport • NT synthesis • Storage • Release • Activation • Termination ~

  4. Postsynaptic Membrane Presynaptic Axon Terminal Terminal Button Dendritic Spine

  5. 1. Precursor Transport

  6. _ _ _ NT 2. Synthesis enzymes/cofactors

  7. 3. Storage in vesicles

  8. NT Vesicles Terminal Button Dendritic Spine Synapse

  9. 4. Release Terminal Button Dendritic Spine Synapse Receptors

  10. Terminal Button Dendritic Spine AP Synapse

  11. Exocytosis Ca++

  12. 5. Activation

  13. 6. Termination

  14. 6. Termination by... Diffusion

  15. 6. Termination by... Enzymatic degradation

  16. 6. Termination by... Reuptake

  17. 6. Termination by... Autoreceptors A

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

  19. Receptor Activation • Ionotropic channel • directly controls channel • fast • Metabotropic channel • second messenger systems • receptor indirectly controls channel ~

  20. Channel Ionotropic Channels neurotransmitter NT

  21. NT Pore Ionotropic Channels

  22. Ionotropic Channels NT

  23. NT Ionotropic Channels

  24. Metabotropic Channels • Receptor separate from channel • 2d messenger system • G proteins • cAMP • other types • Effects • Control channel • Alter properties of receptors • regulation of gene expression ~

  25. G protein: direct control • NT is 1st messenger • G protein binds to channel • opens or closes • relatively fast ~

  26. R G GDP G protein: direct control

  27. R G GTP G protein: direct control Pore

  28. G protein: Protein Phosphorylation • Open or close channels at resting Vm • NT = 1st messenger • Membrane-associated components • Receptor • Transducer • Primary effector • Intracellular • 2d messenger • Secondary effector ~

  29. Receptor Receptor b adrenergic -R trans- ducer trans- ducer primary effector primary effector adenylyl cyclase G protein: Protein Phosphorylation external signal: nt external signal: nt norepinephrine GS 2d messenger 2d messenger cAMP secondary effector secondary effector protein kinase

  30. A C R G GDP G protein: Protein Phosphorylation PK

  31. A C R G GTP G protein: Protein Phosphorylation ATP cAMP PK

  32. A C R G GTP Pore G protein: Protein Phosphorylation ATP P cAMP PK

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