1. Synaptic Transmission
Lesson 11

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

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

4. Postsynaptic
Membrane
Presynaptic
Axon Terminal
Terminal
Button
Dendritic
Spine

5. 1. Precursor
Transport

6. 1. Precursor
Transport

7. 2. Synthesis
Enzymes & cofactors ~ E

8. 3. Storage E

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

10. 4. Release
via exocytosis
diffusion
Ca++

11. 4. Release
via exocytosis
diffusion AP
Synapse
Ca++

12. 4. Release
via exocytosis
diffusion
Ca++

13. Exocytosis: Membrane Fusion
Ca2+ influx
Ca2+ -Calmodulin
synapsin
SNAPs
soluble-NSF-attachment proteins
Cell membrane
SNAREs
SNAP receptors
Vesicle & cell membrane~
NSF = NEM sensitive fusion protein
it is an ATPase

14. 5. Activation
NT binds to receptor

15. Activation NT binds to postsynaptic receptor opens ion channel EPSP
Na+ into cell
or IPSP
K+ out of cell ~

16. 6. Termination
4 basic methods

17. 6. Termination
diffusion

18. 6. Termination
Enzymatic degradation

19. 6. Termination
Presynaptic reuptake
active transport

20. 6. Termination
autoreceptors A

21. Autoreceptors On presynaptic terminal Binds NT
same as postsynaptic receptors
different receptor subtype
Decreases NT release & synthesis ~

22. Termination Must have discrete signal
What if ion channels continually open?
ions move toward equilibrium
membrane no longer polarized
no EPSPs or IPSPs
Disrupts neural communication
Termination  neuron repolarizes ~

23. Axoaxonic Synapses Modulation of NT release Presynaptic Facilitation
Increases NT release
Presynaptic Inhibition
decreases NT release
Via modulation of Em
Ca2+, K+, and Cl- ~