The Neurotransmitters are endogenous chemicals which transmit signals from a neuron to the target cell across a synapse. The Neurotransmitters are packaged into synaptic vesicles clustered underneath the membrane in the axon terminal, on the presynaptic side of the synapse. They are released and diffuse across the synaptic cleft, where they bind to particular receptors in the membrane on the postsynaptic side of the synapse. The release of neurotransmitters generally follows entrance of an action potential at the synapse, but it may also follow graded electrical potentials. The low level "baseline" release also takes place without electrical stimulation. The Neurotransmitters are synthesized from plentiful and simple precursors, like amino acids, that are readily available from the diet and that need only a small number of biosynthetic steps to convert.