The huge number of nerve cells and the even larger number of communication points between nerve cells makes the human brain the most complicated and mysterious machine that we know about, other than the universe itself. The complexity of the human brain makes it possible for our brains to produce emotional behavior and to carry out complex functions such as learning and the creation of new ideas, the very essence of being human. However, the complexity of the human brain makes it hard to study. Over the past decade neuroscientists have studied how nerve cells communicate with each other. Most drugs used today to treat neurodegenerative disease and mental illness, alter the communication between nerve cells to help people suffering from these brain diseases.
Nerve cells communicate with each other by making many connections with other nerve cells.
The point where they physically connect is called a synapse. At these connections or synapses nerve cells send off molecules, called neurotransmitters, which spread across the connection point or synapse. This means that many of the legal and illegal drugs that we use change the normal function of the communication between nerve cells and alter the way in which the brain functions. Under controlled conditions these drugs can be beneficial and help people with depression, schizophrenia and other neurological diseases. Hundreds of neurotransmitter receptor genes have been discovered, cloned and studied in some detail.