What is a synapse?
There are several types of synapses in the body. The most
commonly discussed type is the chemical synapse, but other
types of synapses include electrical synapses and
immunological synapses. Because chemical synapses are the
most commonly discussed synapses in general, that's probably what
this question is referring to.
A chemical synapse is a small gap, or commonly referred to as a
connection, between two cells that allows for the first cell (the
presynaptic cell) to communicate with the second cell (the
postsynaptic cell) through a chemical signal. These chemical
signals are called neurotransmitters, and once they are
released by the presynaptic cell, they act on the postsynaptic cell
through specialized protein molecules called neurotransmitter
The actions triggered by a neurotransmitter binding its receptor
on the postsynaptic cell are highly varied. They vary according to
the type, quantity, and frequency of neurotransmitter release, the
specific receptor involved, the type of cell that is receiving the
neurotransmitter signal, among other things. For example, a
neurotransmitter called glutamate typically causes activation of
the postsynaptic cell, while a neurotransmitter called GABA
typically inhibits postsynaptic cells. Likewise, if the
postsynaptic cell belongs to a gland, then activity in that cell
may promote secretion, while inhibition may hinder secretion. If
the postsynaptic cell is a muscle fiber, then activation triggers
muscle contraction, while inhibition causes relaxation.
A synapse is a connection which allows for the transmission of
nerve impulses. Synapses can be found at the points where nerve
cells meet other nerve cells, and where nerve cells interface with
glandular and muscular cells. In all cases, this connection allows
for the one-way movement of data. The human body contains trillions
of synapses, and at any given time, huge numbers of these
connections are active.