Synaptic Transmission Lesson 11 Synapses Signaling between neurons
Synaptic Transmission Lesson 11
Synapses Signaling between neurons l chemical l few electric n Chemical synapse types l axodendritic l axosomatic l axoaxonic l dendrodendritic ~ n
Synaptic Events Action Potential reaches axon terminal n Chemical substance released l Neurotransmitter (NT) n Diffuses across synapse n Binds to receptor protein l EPSP or IPSP ~ n
Synaptic Transmission Model 1. 2. 3. 4. 5. 6. Precursor transport NT synthesis Storage Release Activation Termination ~
Presynaptic Axon Terminal Button Postsynaptic Membrane Dendritic Spine
1. Precursor Transport
2. Synthesis l Enzymes & cofactors l Can be multiple steps ~ E
3. Storage In vesicles E
3. Storage In vesicles Terminal Button Dendritic Spine Synapse
4. Release AP Ca++ Synapse
4. Release diffusion Ca++
5. Activation l NT binds to receptor
Activation n NT binds to postsynaptic receptor l opens ion channel l EPSP l or IPSP ~
6. Termination n 4 Basic methods l Diffusion l Enzymatic degradation l Presynaptic reuptake uactive l transport Autoreceptors ~
6. Termination E A RU E
Autoreceptors On presynaptic terminal n Binds NT l same as postsynaptic receptors l different receptor subtype n Decreases NT release & synthesis l via 2 d messenger system ~ n
Termination Must have discrete signal n What if ion channels continually open? n Disrupts neural communication n Termination neuron repolarizes ~ n
Drug Interaction Terms Drug’s effect on synaptic transmission l Direct at postsynaptic receptor l Indirect at any other step n Agonist (AG) l mimics or NT effects n Antagonist (ANT) l blocks or ¯ NT effects ~ n
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