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Synaptic transmission

Synaptic transmission

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Synaptic transmission

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  1. Synaptic transmission Communication between neurons and other body cells: Other neurons, glands, and muscles

  2. Chemical communication • Neurotransmitters • Neuromodulators and ectopic synapses • Hormones • Pheromones

  3. Structure of the synapse Terminal button and presynaptic membrane Synaptic vesicles: small and large Synaptic gap Post-synaptic membrane and receptor sites/ receptor density Autoreceptors

  4. Synaptic transmission

  5. The process: Presynaptic • Preparation: Docked vesicles • Arrival of the action potential • Opening of voltage-dependent calcium channels • Separation of docking proteins opens fusion pore • Wfigures

  6. The process: Postsynaptic • Momentary affinity and binding • Neurotransmitter-dependent ion channels • A. Ionotropic receptors • B. Metabotropic receptors • 1. G-proteins a subunit to ion channels • 2. G-proteins a subunit to second messengers • cAMP, cGMP to • a. ion channels, or • b. nucleus

  7. Postsynaptic potentials • EPSP • Na+ channels open, Na+ enters • If Cl- channels open, Na+ EPSP is limited • Ca2+ channels open, Ca2+ enters • This affects not only the EPSP, but also binds with proteins to activate enzymes • IPSP • K+ channels open, K+ leaves • Cl- channels open

  8. Summation • Temporal summation • Spatial summation • Graded potentials • Cable conduction

  9. Stopping the process • Reuptake • From cleft by transporters to sending cell • Assisted by glial cells? • Second step: Re-storing in vesicles • Enzyme action • Acetylcholine esterase (AChE) in cleft • MAO and COMT are inside terminal button, so are not involved in stopping transmission

  10. Axoaxonic synapses • Presynaptic inhibition • Presynaptic facilitation • Dendrodendritic synapses • Chemical • Ionic (Gap junctions) • Retrograde synapses • CO and NO feedback from postsynaptic cell to presynaptic cell: Agonistic effect

  11. Other chemical communication • Neuromodulators • Hormones • Peptides act on metabotropic receptors with second messengers • Steroids • act on receptors in the nucleus • act on synapses, with a rapid effect on synaptic transmission