1. Synaptic Transmission
Lesson 11

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

3. Synaptic Events Action Potential reaches axon terminal
Chemical substance released
Neurotransmitter (NT)
Diffuses across synapse
Binds to receptor protein
EPSP or IPSP ~

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

5. Postsynaptic
Membrane
Presynaptic
Axon Terminal
Terminal
Button
Dendritic
Spine

6. 1. Precursor
Transport

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

8. 3. Storage
In vesicles E

9. 3. Storage
In vesicles
Terminal
Button
Dendritic
Spine
Synapse

10. 4. Release AP
Synapse
Ca++

11. 4. Release
diffusion
Ca++

12. 5. Activation
NT binds to receptor

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

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

15. 6. Termination E A RU E

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

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

18. 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 ~