Synaptic transmission occurs at a synapse between a presynaptic neuron and a postsynaptic neuron, allowing them to communicate with each other. Once the electrical impulse, also known as an action potential, in the presynaptic neuron has travelled down the axon and reached the axon terminals, small sacs called vesicles release a neurotransmitter into the synaptic cleft. This neurotransmitter can be excitatory or inhibitory, and it will bind to receptors on the postsynaptic neuron, where either an electrical impulse continues down the neuron if it is excitatory, or the process stops if it is inhibitory.