Why does sympathetic activation produce longer-lasting effects than parasympathetic activation?

Sympathetic activation lasts longer because it releases adrenal medullary hormones, norepinephrine and epinephrine, into the blood, which reinforce and prolong sympathetic effects for several minutes until the liver destroys them. In contrast, parasympathetic fibers release acetylcholine, which is quickly destroyed by acetylcholinesterase, producing short-lived, localized effects.

Parasympathetic effects are brief and localized because acetylcholine is rapidly hydrolyzed by acetylcholinesterase, and each preganglionic parasympathetic neuron synapses with only one or a few postganglionic neurons. Sympathetic effects are diffuse and longer lasting because preganglionic sympathetic axons branch profusely and synapse with many postganglionic neurons. Sympathetic activation also stimulates adrenal medullary cells to secrete norepinephrine and epinephrine into the blood. These circulating hormones have essentially the same effects as norepinephrine released by sympathetic neurons, and they continue to act for several minutes until the liver destroys them. At any given time, these adrenal medullary hormones produce 25–50% of all sympathetic effects on the body.