Role of Neurotransmitters

Neurons communicate with one another through the release of neurotransmitters,
chemical substances that transmit nerve impulses between
nerve cells. Numerous types of neurotransmitters have been identified.
Some of these transmitters act to excite neurons, while others inhibit
neuronal activity. The particular type of transmitter is synthesized within the
cell body of the neuron, travels along the axon, and is released into the
space between neurons, known as the synapse.
Among the most prominent neurotransmitters involved in the excitation
of neurons is acetylcholine. The same transmitter bridges the junctions between
nerves and skeletal muscles as well as glandular tissues in the body. In
the brain, acetylcholine bridges the synapses between neurons throughout
the central nervous system. The amino acids glutamic acid and aspartic acid
are also known to be involved in excitation of some neurons within the
brain. The neurotransmitter serotonin is released mainly within the brain
stem, where it appears to regulate activities such as sleep, moods, and body
temperature.
Certain neurotransmitters serve in the inhibition of neuronal activity.
The most common of these is gamma-aminobutyric acid (GABA), found
primarily in the diencephalon region of the brain. Here GABA acts to reduce
the activity within the region. Antianxiety drugs such as valium or librium
appear to work by enhancing the activity of GABA, resulting in the relaxation
of skeletal muscles. Antidepression compounds such as Prozac and
Zoloft appear to function through blockage of serotonin uptake by neurons.