Transmission

• (1) An action potential triggers Calcium Influx

  • An action potential arrives at the synaptic knob of the presynaptic neurone which stimulates voltage gated calcium ion channels in the presynaptic neurone to open.
  • Calcium ions diffuse into the synaptic knob.
• (2) Calcium Influx causes Neurotransmitter Release

  • The influx of calcium ions into the synaptic knob causes the synaptic vesicles to move to the presynaptic membrane. They then fuse with the presynaptic membrane.
  • The vesicles release the neurotransmitter into the synaptic cleft by exocytosis.
• (3) The Neurotransmutter Triggers and Action Potential in the Postsynaptic Neurone

  • Neurotransmitter diffuses across the synaptic cleft and binds to specific receptors on the postsynaptic membrane. This causes sodium ion channels to open in the postsynapse. This influx of sodium causes depolarisation. Generating an action potential is threshold is reached.