Final answer:
In the sympathetic system, sweat glands are activated by the release of ACh instead of norepinephrine. ACh binds to muscarinic receptors in the sweat glands, leading to sweat production and secretion. There is no parasympathetic input to the sweat glands.
Step-by-step explanation:
In the sympathetic system, the postganglionic sympathetic fibers that contact sweat glands release ACh instead of norepinephrine. Sweat glands have muscarinic receptors and produce and secrete sweat in response to the presence of ACh. There is no parasympathetic input to the sweat glands.