BN12synaptictransmissionpptbn12突触transmissionppt.ppt

1、Synaptic Transmission,Lesson 12,Synapses,Communication b/n neurons Electrical Electrotonic conduction Chemical Ligand / receptor ,Electrical Synapses,Tight junctions Connexons Passive current & larger molecules (e.g., ATP) Synchronous activity Breathing Hormone release from hypothalamus ,Synaptic Ev

2、ents,Action Potential reaches axon terminal Chemical substance released Neurotransmitter (NT) Diffuses across synapse Binds to receptor protein EPSP or IPSP ,1. Precursor transport 2. NT synthesis 3. Storage 4. Release 5. Activation 6. Termination ,Synaptic Transmission Model,Presynaptic Axon Termin

3、al,Postsynaptic Membrane,Terminal Button,Dendritic Spine,1. Precursor Transport,E,2. Synthesis,Enzymes & cofactors ,3. Storage,E,Synapse,Terminal Button,Dendritic Spine,3. Storage,In vesicles,Synapse,4. Release,via exocytosis diffusion,Exocytosis: Membrane Fusion,Ca2+ influx 2d messenger Ca2+ -Calmo

4、dulin SNAPs soluble-NSF-attachment proteins SNAREs SNAP receptors ,5. Activation,NT binds to receptor,Activation,NT binds to postsynaptic receptor opens ion channel EPSP Na+ into cell or IPSP K+ out of cell ,6. Termination,4 Basic methods Diffusion Enzymatic degradation Presynaptic reuptake active t

5、ransport Autoreceptors ,6. Termination,autoreceptors,A,Autoreceptors,On presynaptic terminal Binds NT same as postsynaptic receptors different receptor subtype Decreases NT release & synthesis ,Termination,Must have discrete signal What if ion channels continually open? ions move toward equilibrium

6、membrane no longer polarized no EPSPs or IPSPs Disrupts neural communication Termination - neuron repolarizes ,Axoaxonic Synapses,Modulation of NT release *via or Ca2+ influx Presynaptic Facilitation Increases NT release Presynaptic Inhibition decreases NT release Via modulation of Em Ca2+, K+, and Cl- ,Drug Interaction Terms,Drugs effect on synaptic transmission Direct at postsynaptic receptor I