premise: Acetylcholine induces neuromodulation.
hypothesis: Acetylcholine ( ACh ) is an organic chemical that functions in the brain and body of many types of animals , including humans , as a neurotransmitter -- a chemical released by nerve cells to send signals to other cells . Acetylcholine is the neurotransmitter used at the neuromuscular junction -- in other words , it is the chemical that motor neurons of the nervous system release in order to activate muscles . Acetylcholine is also used as a neurotransmitter in the autonomic nervous system , both as an internal transmitter for the sympathetic nervous system and as the final product released by the parasympathetic nervous system . In the brain , acetylcholine functions as a neurotransmitter and as a neuromodulator . Neuromodulation . Major neuromodulators in the central nervous system include dopamine , serotonin , acetylcholine , histamine , and norepinephrine .