Synaptic Transmission Lecture 12
Synapses <ul><li>Communication b/n neurons </li></ul><ul><li>Electrical </li></ul><ul><ul><li>Electrotonic conduction </li...
Electrical Synapses <ul><li>Tight junctions </li></ul><ul><ul><li>Connexons </li></ul></ul><ul><ul><li>Passive current </l...
Synaptic Transmission <ul><li>Nature of signal across synapse? </li></ul><ul><li>Sherrington  </li></ul><ul><ul><li>electr...
Synaptic Transmission <ul><li>Otto Loewi had a dream  </li></ul><ul><ul><li>Chemical Signal? </li></ul></ul><ul><ul><li>Ho...
<ul><li>Stimulate Vagus </li></ul><ul><ul><li>Heart rate slows ~ </li></ul></ul>electrical  stimulation -
<ul><li>Stimulate A </li></ul><ul><ul><li>Collect fluid ~ </li></ul></ul>A B -
<ul><li>Perfuse heart B </li></ul><ul><li>Heart B slows </li></ul><ul><ul><li>chemical = vagusstoff  ~ </li></ul></ul>A B -
<ul><li>Repeat w/  accelerator nerve </li></ul><ul><ul><li>HR increases  </li></ul></ul><ul><ul><li>Acceleransstoff ~ </li...
The Chase Is On <ul><li>Search for chemical neurotransmitters (NT) </li></ul><ul><li>Criteria </li></ul><ul><li>Synaptic M...
Synaptic Events <ul><li>Action Potential reaches axon terminal </li></ul><ul><li>Chemical substance released </li></ul><ul...
<ul><li>1.  Precursor transport </li></ul><ul><li>2.  NT synthesis </li></ul><ul><li>3.  Storage </li></ul><ul><li>4.  Rel...
Presynaptic Axon Terminal 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  <ul><li>via exocytosis </li></ul><ul><li>diffusion </li></ul>Ca++ AP
Exocytosis: Membrane Fusion <ul><li>Ca 2+  influx </li></ul><ul><ul><li>2 d  messenger </li></ul></ul><ul><ul><li>Ca 2+  -...
<ul><ul><li>NT binds to receptor </li></ul></ul>5.  Activation
Activation <ul><li>NT binds to postsynaptic receptor </li></ul><ul><ul><li>opens ion channel </li></ul></ul><ul><ul><li>EP...
6. Termination <ul><li>4 Basic methods </li></ul><ul><ul><li>Diffusion </li></ul></ul><ul><ul><li>Enzymatic degradation </...
<ul><ul><li>autoreceptors </li></ul></ul>6.  Termination  A
Autoreceptors <ul><li>On  presynaptic  terminal </li></ul><ul><li>Binds NT </li></ul><ul><ul><li>same as postsynaptic rece...
Termination <ul><li>Must have discrete signal </li></ul><ul><li>What if ion channels continually open? </li></ul><ul><ul><...
Exocytosis: Membrane Fusion <ul><li>Ca 2+  influx </li></ul><ul><ul><li>2 d  messenger </li></ul></ul><ul><ul><li>Ca 2+  -...
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  • NSF = NEM sensitive fusion protein it is an ATPase
  • NSF = NEM sensitive fusion protein it is an ATPase
  • Transcript of "~BN12 synaptic transmission.ppt"

    1. 1. Synaptic Transmission Lecture 12
    2. 2. Synapses <ul><li>Communication b/n neurons </li></ul><ul><li>Electrical </li></ul><ul><ul><li>Electrotonic conduction </li></ul></ul><ul><li>Chemical </li></ul><ul><ul><li>Ligand / receptor ~ </li></ul></ul>
    3. 3. Electrical Synapses <ul><li>Tight junctions </li></ul><ul><ul><li>Connexons </li></ul></ul><ul><ul><li>Passive current </li></ul></ul><ul><ul><li>& larger molecules (e.g., ATP) </li></ul></ul><ul><li>Synchronous activity </li></ul><ul><ul><li>Breathing </li></ul></ul><ul><ul><li>Hormone release from hypothalamus ~ </li></ul></ul>
    4. 4. Synaptic Transmission <ul><li>Nature of signal across synapse? </li></ul><ul><li>Sherrington </li></ul><ul><ul><li>electrotonic transmission </li></ul></ul><ul><li>Most neural conduction too slow </li></ul><ul><ul><li>Delay in spinal reflexes ~ </li></ul></ul>
    5. 5. Synaptic Transmission <ul><li>Otto Loewi had a dream </li></ul><ul><ul><li>Chemical Signal? </li></ul></ul><ul><ul><li>How can it be demonstrated? </li></ul></ul><ul><li>Frog Heart Preparation ~ </li></ul>
    6. 6. <ul><li>Stimulate Vagus </li></ul><ul><ul><li>Heart rate slows ~ </li></ul></ul>electrical stimulation -
    7. 7. <ul><li>Stimulate A </li></ul><ul><ul><li>Collect fluid ~ </li></ul></ul>A B -
    8. 8. <ul><li>Perfuse heart B </li></ul><ul><li>Heart B slows </li></ul><ul><ul><li>chemical = vagusstoff ~ </li></ul></ul>A B -
    9. 9. <ul><li>Repeat w/ accelerator nerve </li></ul><ul><ul><li>HR increases </li></ul></ul><ul><ul><li>Acceleransstoff ~ </li></ul></ul>B A +
    10. 10. The Chase Is On <ul><li>Search for chemical neurotransmitters (NT) </li></ul><ul><li>Criteria </li></ul><ul><li>Synaptic Model ~ </li></ul>
    11. 11. Synaptic Events <ul><li>Action Potential reaches axon terminal </li></ul><ul><li>Chemical substance released </li></ul><ul><ul><li>Neurotransmitter (NT) </li></ul></ul><ul><li>Diffuses across synapse </li></ul><ul><li>Binds to receptor protein </li></ul><ul><ul><li>EPSP or IPSP ~ </li></ul></ul>
    12. 12. <ul><li>1. Precursor transport </li></ul><ul><li>2. NT synthesis </li></ul><ul><li>3. Storage </li></ul><ul><li>4. Release </li></ul><ul><li>5. Activation </li></ul><ul><li>6. Termination ~ </li></ul>Synaptic Transmission Model
    13. 13. Presynaptic Axon Terminal Postsynaptic Membrane Terminal Button Dendritic Spine
    14. 14. 1. Precursor Transport
    15. 15. E 2. Synthesis Enzymes & cofactors ~
    16. 16. 3. Storage E
    17. 17. Synapse Terminal Button Dendritic Spine 3. Storage In vesicles
    18. 18. Synapse 4. Release <ul><li>via exocytosis </li></ul><ul><li>diffusion </li></ul>Ca++ AP
    19. 19. Exocytosis: Membrane Fusion <ul><li>Ca 2+ influx </li></ul><ul><ul><li>2 d messenger </li></ul></ul><ul><ul><li>Ca 2+ -Calmodulin </li></ul></ul><ul><li>SNAPs </li></ul><ul><ul><li>soluble-NSF-attachment proteins </li></ul></ul><ul><li>SNAREs </li></ul><ul><ul><li>SNAP receptors ~ </li></ul></ul>
    20. 20. <ul><ul><li>NT binds to receptor </li></ul></ul>5. Activation
    21. 21. Activation <ul><li>NT binds to postsynaptic receptor </li></ul><ul><ul><li>opens ion channel </li></ul></ul><ul><ul><li>EPSP </li></ul></ul><ul><ul><ul><li>Na+ into cell </li></ul></ul></ul><ul><ul><li>or IPSP </li></ul></ul><ul><ul><ul><li>K+ out of cell ~ </li></ul></ul></ul>
    22. 22. 6. Termination <ul><li>4 Basic methods </li></ul><ul><ul><li>Diffusion </li></ul></ul><ul><ul><li>Enzymatic degradation </li></ul></ul><ul><ul><li>Presynaptic reuptake </li></ul></ul><ul><ul><ul><li>active transport </li></ul></ul></ul><ul><ul><li>Autoreceptors ~ </li></ul></ul>
    23. 23. <ul><ul><li>autoreceptors </li></ul></ul>6. Termination A
    24. 24. Autoreceptors <ul><li>On presynaptic terminal </li></ul><ul><li>Binds NT </li></ul><ul><ul><li>same as postsynaptic receptors </li></ul></ul><ul><ul><li>different receptor subtype </li></ul></ul><ul><li>Decreases NT release & synthesis ~ </li></ul>
    25. 25. Termination <ul><li>Must have discrete signal </li></ul><ul><li>What if ion channels continually open? </li></ul><ul><ul><li>ions move toward equilibrium </li></ul></ul><ul><ul><li>membrane no longer polarized </li></ul></ul><ul><ul><li>no EPSPs or IPSPs </li></ul></ul><ul><li>Disrupts neural communication </li></ul><ul><li>Termination ---> neuron repolarizes ~ </li></ul>
    26. 26. Exocytosis: Membrane Fusion <ul><li>Ca 2+ influx </li></ul><ul><ul><li>2 d messenger </li></ul></ul><ul><ul><li>Ca 2+ -Calmodulin </li></ul></ul><ul><li>SNAPs </li></ul><ul><ul><li>soluble-NSF-attachment proteins </li></ul></ul><ul><li>SNAREs </li></ul><ul><ul><li>SNAP receptors ~ </li></ul></ul>
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