CAROL & MIKE WERNER / VISUALS UNLIMITED, INC. / SCIENCE PHOTO LIBRARY CAROL & MIKE WERNER / VISUALS UNLIMITED, INC. / SCIENCE PHOTO LIBRARY
Biomedical illustration of the synthesis of norepinephrine in a nerve cell. The amino acid tyrosine is transported into the sympathetic nerve axon where it is converted to DOPA (L-3,4 dihydroxyphenylalanine) by tyrosine hydroxylase. DOPA is converted to dopamine by DOPA decarboxylase and dopamine can be converted to norepinephrine by dopamine beta-hydroxylase. An electric potential traveling down the axon depolarizes the membrane and causes calcium to enter the axon, which causes the vesicles to migrate to and fuse with the axon membrane, which permits the norepinephrine to diffuse out of the vesicle into the synapse where it binds to the postjunctional receptor and stimulates a response. This series of events, along with epinephrine production is.
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