Pyridostigmine stops cholinesterase from breaking down acetylcholine at the junctions between the nerves and the muscle cells. This prolongs the action of acetylcholine at the nerve endings and gives it more chance to act on the remaining acetylcholine receptors. Pyridostigmine thus increases the likelihood of a nerve signal being successfully transmitted to the muscle. It improves nerve transmission both to muscles that are under voluntary control, as well as those that are not, for example the muscle in the gut. It thus allows these muscles to function normally.