Synaptic transmission

• Step 1: An action potential arrives at synaptic knob. Depolarisation of synaptic knob leads to the Ca 2+ channels and Ca2+ diffuse into synaptic knob.
• Step 2: Vesicles containing neurotransmitter move towards and fuse with the pre-synaptic membrane. Neurotransmitter is released to the synaptic cleft.
• Step 3: Neurotransmitter diffuses down the concentration gradient across the synaptic cleft, to post-synaptic membrane; neurotransmitter binds to the complementary shape of receptors.
• Step 4: Na+ channels on the post-synaptic membrane open and Na+ diffuse in and from this post-synaptic neuron becomes depolarised.
• Step 5: Neurotransmitter is then broken down by an enzyme they can be reabsorbed back into the pre-synaptic neurone.