synaptic transmission

• Synaptic transmission


  The process by which neighbouring neurons communicate with each other by sending chemical messages across the gap that separates them.
• Neurotransmitter


  Chemicals released from synaptic vesicles that relay signals across the synapse from one neuron to the next. Can perform either excitatory or inhibitory functions
• A synapse between two neurones

  synapse

  A) vesicles

  B) pre-synaptic membrane

  C) synaptic cleft

  D) post-synaptic membrane

  E) neurotransmitter receptor

  
• Why does the message pass in one direction along a neuron?


  Action potential only travels in one direction to make the communication system fast & efficient. Vesicles which have the neurotransmitters are only on the pre-synaptic neuron terminal button whilst the receptors sites are only on the post synaptic dendrite to make sure this happens
• Process of synaptic transmission


  An impulse arrives at the end of the presynaptic neuron. Vesicles move towards & fuse with the pre-synaptic membrane this releases neurotransmitters into the synaptic cleft. Neurotransmitters diffuse across the synaptic cleft. Neurotransmitters attach to receptors on the post-synaptic membrane. This triggers an impulse which travels along the post-synaptic membrane. The neurotransmitters are recycled or destroyed once an impulse is sent
• Excitatory synapse

  Increases the chance of the next neuron to fire & pass on the impulse, the neuron becomes positively charged so more likely to fire
• Inhibitory synapse

  Decreases the chance of the next neuron to fire & pass on the impulse, the neuron remains negatively charged so less likely to fire
• Summation

  Each neurone brings an electrical charge to the synapse , these voltages add together- a summation. If the electrical charge reaches 1-2mv this will trigger the action potential to be triggered: excitatory synapse