Dopamine Dopamine plays several different roles in the brain. Dopamine is thought to release chemicals that allow us to feel pleasure. A lack of dopamine in the brain can produce Parkinson's Disease or schizophrenia. All of the functions of dopamine are not yet known. The sympathetic nervous system stimulates the heart, blood vessels, sweat glands, the large interior organs, and the adrenal medulla in the brain.
Norepinephrine causes physiological expressions of fear and anxiety.
People with anxiety disorders have been found to have an excess of norepinephrine.