ABSTRACT
A chemical synapse is formed from the close approximation of an axon terminal, which is the presynaptic component, with some region of the postsynaptic cell. There are two types of synapse, electrical and chemical, but chemical synapses far outnumber electrical ones. Synapses are made on all regions of a receiving cell and may be classified on the basis of where they are located. Particularly powerful synapses are made between axons and the cell body of a postsynaptic cell. These are called axosomatic synapses, the word somatic coming from the alternative term for the cell body, soma. Synapses between axon terminals and axons of postsynaptic neurons are said to be axoaxonal. The cell membrane of the dendrite in the region of the synapse appears thickened to form the postsynaptic density. This is caused by the accumulation of proteins, receptors, enzymes and the like, involved in the postsynaptic cells' response to transmitter.
