The Synapse

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The Synapse

  1. 1. THE SYNAPSE Where the electrical signal becomes chemical
  2. 2. Nervous System Divisions  We discussed the nervous system as an input-output device both on the cellular level and system level  Remember that there are three types of neural cells: sensory neurons take in signals interneurons process signals motor neurons send out signals
  3. 3. Synaptic transmission: communication between neurons
  4. 4.  The synapse is the meeting point between two neurons.  The outgoing signal from the presynaptic neuron is passed to the postsynaptic neuron.  The signal comes from the presynaptic (axon / dendrite) and goes into the postsynaptic (axon / dendrite)
  5. 5.  There are two kinds of synapses that connect neurons.  Electrical synapses are direct connections between neurons.  Chemical synapses are small gaps between neurons where chemicals are triggered to diffuse. Electrical vs. Chemical Synapses
  6. 6. Electrical vs. Chemical Synapses
  7. 7. Electrical Synapses  Pores connect the two cells.  Ions from the presynaptic action potential diffuse directly into the postsynaptic neuron.  These signals are transmitted fast!
  8. 8. Chemical Synapse  When the action potential reaches the synapse, it triggers the release of little bubbles called vesicles.  The vesicles contain chemical signals called neurotransmitters. They are bigger, and diffuse slower, than ions.  Neurotransmitters must be received by specific receptors in the post-synaptic neuron.
  9. 9. Chemical Synapse 1. Action potential in presynaptic neuron. 2. Vesicle release is triggered. 3. Neurotransmitters release into synapse. 4. Neurotransmitters bind to receptors. 5. Ion channels are triggered to open.
  10. 10. 1. Action potential arrives at terminal button Membrane receptor for neurotransmitter Vesicle storing neurotransmitter © 2008 Paul Billiet ODWS
  11. 11. Ca2+ Ca2+ Ca2+ Ca2+ 2. Vesicles fuse with membrane 3. Neurotransmitter is released; diffuses across gap. © 2008 Paul Billiet ODWS
  12. 12. 5. Ion channels are triggered to open 4. Neurotransmitter binds to receptors on the postsynaptic neuron © 2008 Paul Billiet ODWS
  13. 13. 7. Neurotransmitter destroyed by enzymes in the cleft. Stops signal being perpetuated. 6. Action potential generated which travels down the postsynaptic cell. © 2008 Paul Billiet ODWS
  14. 14. Why Chemical Synapses?  Chemical synapses are slower than electrical synapses, so why does our body rely on them?  Check out your handout on neurotransmitters to see some ideas.

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