The cause of fibromyalgia is unknown; however, it is believed to involve a combination of genetic and environmental factors with half the risk attributed to each. The condition runs in families and many genes are believed to be involved.
Agonist: A substance that acts like another substance and therefore stimulates an action. Agonist is the opposite of antagonist. Antagonists and agonists are key players in the chemistry of the human body and in pharmacology.
agonist - a muscle that contracts while another relaxes; when bending the elbow the biceps are the agonist antagonistic muscle - (physiology) a muscle that opposes the action of another; the biceps and triceps are antagonistic muscles