4. Synaptic transmission

• Neural networks


  Neurons communicate with each other in groups
• Synapse


  Each neurone separated from the next by a synapse, includes the synaptic cleft, presynaptic terminal and post synaptic receptor sites
• Synaptic transmission


  Signals between neurons are transmitted chemically through the synapse
• How does synaptic transmission occur?

  1. Electrical impulse reaches the end of the neurone (presynaptic terminal)

  2. Triggers the release of a neurotransmitter from tiny sacs called synaptic vesicles
• Neurotransmitters


  Chemicals that are released from synaptic vessels
• Neurotransmitter release


  1. Diffuse across the synaptic cleft

  2. Taken up by post synaptic receptor sites – found on dendrites of the next neurone
• Receptor sites


  Each neurone has specific molecular structure which fits perfectly into receptor sites
• Excitatory neurotransmitter


  Increases the positive charge of the post synaptic neurone, increases the likelihood that the neurone will fire (pass on the electrical impulse), increases action potential
• Inhibitory neurotransmitter


  Makes the charge of the postsynaptic neurone more negative, decreases the likelihood that the neuron will fire (pass on the electrical impulse), reduces action potential
• Summation


  The action potential will only be generated in post synaptic neurone if the sum of excitatory and inhibitory signals reach the threshold