Synapses and neurotransmitters

Synapses and neurotransmitters

1. CNS synapses

   • Axodendritic
   • Axosomatic
   • Dendrodendritic

2. Synapses

   • Secretory granules contain soluble protein
     • Dense-core vesicles
   • Presynaptic neurone
     • Active zone
   • Postsynaptic neurone
     • Postsynaptic density

3. Electrical synapses

   • Fastest and most primitive
   • Direct transfer of ionic current
     • Synchronous activity
   • Gap junctions are bi-directional
     • Glia-neuron synapse
     • Glia-glia synapse
     • Cardiac myocytes

4. Chemical synapses

   • Action potential causes depolarisation
     • Voltage-gated calcium channels open
       • Influx of calcium ions
         • Vesicles fuse with presynaptic membrane
   • Neurotransmitters
     • Amino acids
     • Amines
     • Peptides

5. Ionotropic

   • Binding of transmitter causes conformational change
     • Receptor changes shape
   • Ligand-gated channels open
   • Fast transmission of action potential

6. Metabotropic

   • Binding of transmitter causes conformational change
     • G-protein changes shape
     • Activated G-protein activates effector systems
   • Slower transmission with longer lasting effects