Adrenal gland
The adrenal glands are named for their location relative to the kidneys. The term "adrenal" comes from "ad-" (Latin, "near") and "renes" (Latin, "kidney"). Similarly, "suprarenal", as termed by Jean Riolan the Younger in 1629, is derived from the Latin "supra" () and "renes" (). The suprarenal nature of the glands was not truly accepted until the 19th century, as anatomists clarified the ductless nature of the glands and their likely secretory role – prior to this, there was some debate as to whether the glands were indeed suprarenal or part of the kidney.
Muscarinic acetylcholine receptor
The adrenal medulla is considered a sympathetic ganglion and, like other sympathetic ganglia, is supplied by cholinergic preganglionic sympathetic fibers: acetylcholine is the neurotransmitter utilized at this synapse. The chromaffin cells of the adrenal medulla act as "modified neurons", releasing adrenaline and noradrenaline into the bloodstream as hormones instead of as neurotransmitters. The other postganglionic fibers of the peripheral autonomic system belong to the parasympathetic division; all are cholinergic fibers, and use acetylcholine as the neurotransmitter.