<prompt> When the sympathetic nervous system is activatedNorepinephrine is released by the vascular smooth muscle cellsAcetylcholine is released onto vascular smooth muscle cellsNorepinephrine is released from axons onto the aeriolar wallThe aerioles constrict because nitric oxide production is suppressed  <response>: Nerve fibers, not vascular smooth muscle, release norepinephrine. The norepinephrine from the sympathetic nerves simply diffuses from the axons and binds to specific receptors on smooth muscle cells. 