Illustration of a close-up of the synaptic gap with the presynapse at top and the postsynapse at bottom. Both synapses are distinct regions in dendritic cells, responsible for signal transmission. In the background is a network of nerve cells. This is the moment of the action potential, when electric impulses from the presynapse release neurotransmitters from synaptic vesicles. They are able to bridge the synaptic gap, which consists of chemical substances and bind to specialised receptors on the postsynaptic neuron. Depending on the type of receptor, the signal is either excitatory or inhibitory. At the postsynaptic neuron the chemical transmission is converted back into an electric signal and the impulse is passed forward to the next neuron.