<Tr> <Th> Structure of a typical chemical synapse </Th> </Tr> <Tr> <Td> Postsynaptic density Voltage - gated Ca channel Synaptic vesicle Neurotransmitter transporter Receptor Neurotransmitter Axon terminal Synaptic cleft Dendrite </Td> </Tr> <P> Neurotransmitters are endogenous chemicals that enable neurotransmission . It is a type of chemical messenger which transmits signals across a chemical synapse, such as a neuromuscular junction, from one neuron (nerve cell) to another "target" neuron, muscle cell, or gland cell . Neurotransmitters are released from synaptic vesicles in synapses into the synaptic cleft, where they are received by neurotransmitter receptors on the target cells . Many neurotransmitters are synthesized from simple and plentiful precursors such as amino acids, which are readily available from the diet and only require a small number of biosynthetic steps for conversion . Neurotransmitters play a major role in shaping everyday life and functions . Their exact numbers are unknown, but more than 200 chemical messengers have been uniquely identified . </P> <P> Neurotransmitters are stored in a synapse in synaptic vesicles, clustered beneath the membrane in the axon terminal located at the presynaptic side of the synapse . Neurotransmitters are released into and diffused across the synaptic cleft, where they bind to specific receptors in the membrane on the postsynaptic side of the synapse . </P>

What are the areas of the neuron that secrete neurotransmitters called