Synapse
The Synapse is the junction between the presynaptic terminal button of one neuron and the dendrite, axon, or soma of another postsynaptic neuron.
A very small space called a synaptic gap or a synaptic cleft, approximately 5 nm (nanometers), exists between the presynaptic terminal button and the postsynaptic dendritic spine (hair is 80,000 nm).
In the presynaptic terminal button, there are synaptic vesicles that package together groups of chemicals called neurotransmitters. Neurotransmitters are released from the presynaptic terminal button, travel across the synaptic gap, and activate ion channels on the postsynaptic spine by binding to receptor sites.