Originally Posted by GregD

As you may already know, certain nerve cells or neurons in a part of the brain called the substantia nigra die off or become impaired. Normally, these neurons produce an important brain chemical known as dopamine. Dopamine is a chemical messenger responsible for transmitting signals between the substantia nigra and the next "relay station" of the brain, the corpus striatum, to produce smooth, purposeful muscle activity. Loss of dopamine causes the nerve cells of the corpus striatum to fire out of control, leaving patients unable to direct or control their movements in a normal manner. Therefore we develop a tremor.

GregD