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Synaptic Conduction

Synaptic Conduction

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Synaptic Conduction

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  1. Synaptic Conduction • What happens when an action potential reaches the axon terminals? • Depends on the nature of “synapse” • Synapse = special communication region between two adjacent neurons or neuron and effector cell (i.e., muscle)

  2. Electrical Synapse

  3. Chemical Synapse

  4. 1. action potential arrives at terminal 2. voltage-gated Ca channels open 3. Ca triggers exocytosis of vesicles 4. neurotransmitter is re- leased, binds to re- ceptor 5. ligand-gated Na or K channels open 6. neurotransmitter broken down, taken up 7. synaptic vesicles re- constituted 8. neurotransmitter stored, awaits next impulse Action potential Synaptic vesicle active uptake Ca2+ voltage- gated Ca channel Ca2+ docking protein K+ Postsynaptic cell Na+

  5. Neurotransmitters • Acetylcholine • Monoamines • Norepinephrine • Dopamine • Serotonin • Amino Acids • Polypeptides • Purines • Gases

  6. Cholinergic Synapse

  7. acetylcholine X atropine (antagonist) muscarine (agonist) Muscarinic cholinergic synapse

  8. acetylcholine botulinum toxin X X acetylcholinesterase curare (antagonist) nicotine (agonist) Neuromuscular Junction Nicotinic cholinergic synapse

  9. Transmission at an Adrenergic Synapse

  10. Antidepressants • Monoamine Oxidase Inhibitors (MAOIs) • Tricyclic Antidepressants (TCAs) • Selective Serotonin Reuptake Inhibitors (SSRIs) • Atypical Antidepressants

  11. Monoamine Oxidase Inhibitors • Inhibit the production of the enzyme monoamine oxidase • Increases amount of neurotransmitter at the synapses and alleviates depression • Examples: Nardil, Parnate

  12. Tricyclic Antidepressants • Inhibit the reuptake of neurotransmitters at the synapses and alleviates depression • Improve moods • Stimulate appetite • Increase activity levels • Help people sleep • Have fewer problems than MAOIs • Examples: Pamelor, Elavil

  13. Selective Serotonin Reuptake Inhibitors • More specific than other antidepressants—block the reuptake of Serotonin • Examples: Prozac, Zoloft, Paxil, Celexa

  14. Atypical Antidepressants • Work in a variety of different ways to inhibit breakdown or reuptake of selective neurotransmitters • Most similar to TCAs and SSRIs • Examples: Wellbutrin, Effexor • Side effects: dizziness, weight gain or loss, increased or decreased appetite, and dry mouth