Final answer:
Epinephrine is not both a hormone and neurotransmitter. It acts as a neurotransmitter in postganglionic sympathetic fibers but acts as a hormone when released by the adrenal medulla into the bloodstream.
Step-by-step explanation:
Epinephrine is not considered both a hormone and neurotransmitter because while it acts as a neurotransmitter in the postganglionic sympathetic fibers, it acts as a hormone when released by the adrenal medulla into the bloodstream. Acetylcholine, on the other hand, can be considered a neurotransmitter because it is released by axons at synapses.