When an impulse comes to the synaptic bulb, vesicles containing neurotransmitter to move towards the presynaptic membrane, vesicles fuse with presynaptic membrane, neurotransmitter is released into the synaptic gap where it diffuses accross it and attaches to specific receptor sites on the post synaptic membrane, Receptor sites have a complementary shape to the neurotransmitter, binding of neurotransmitter triggers impulse to postsynaptic neurone, after neurotransmitter is broken down by enzyme in synaptic gap, mitochondria provides energy to reform neurotransmitter