Parkinson's disease involves a breakdown of the nerve cells in the motor area of the brain. As the cells break down, there is a shortage of dopamine.
Dopamine is a neurotransmitter, or chemical that carries messages to the body.
When there is a shortage of dopamine, the messages that regulate movement aren't sent properly. It usually occurs when a person is still. It can worsen with stress . It usually goes away with sleep. The tremor can occur in one or all of the extremities.