 Norepinephrine is synthesized from the amino acid tyrosine by a series of enzymatic steps in the adrenal medulla and <unk> neurons of the sympathetic nervous system . While the conversion of tyrosine to dopamine occurs predominantly in the cytoplasm , the conversion of dopamine to norepinephrine by dopamine β @-@ monooxygenase occurs predominantly inside neurotransmitter vesicles . The metabolic pathway is : 
