Synaptic Transmission Lesson 11

Synapses Signaling between neurons chemical few electric Chemical synapse types axodendritic axosomatic axoaxonic dendrodendritic ~

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 1. Precursor transport 2. NT synthesis 3. Storage 4. Release 5. Activation 6. Termination ~

Postsynaptic Membrane Presynaptic Axon Terminal Terminal Button Dendritic Spine

1. Precursor Transport

2. Synthesis Enzymes & cofactors Can be multiple steps ~ E

3. Storage In vesicles E

3. Storage In vesicles Terminal Button Dendritic Spine Synapse

4. Release AP Synapse Ca++

4. Release diffusion Ca++

5. Activation NT binds to receptor

Activation NT binds to postsynaptic receptor opens ion channel EPSP or IPSP ~

6. Termination 4 Basic methods Diffusion Enzymatic degradation Presynaptic reuptake active transport Autoreceptors ~

6. Termination E A RU E

Autoreceptors On presynaptic terminal Binds NT same as postsynaptic receptors different receptor subtype Decreases NT release & synthesis via 2d messenger system ~

Termination Must have discrete signal What if ion channels continually open? Disrupts neural communication Termination  neuron repolarizes ~

Drug Interaction Terms Drug’s effect on synaptic transmission Direct  at postsynaptic receptor Indirect  at any other step Agonist (AG) mimics or ­ NT effects Antagonist (ANT) blocks or ¯ NT effects ~