Migraine headache is a result of specific changes within the brain. It causes severe head pain that is often accompanied by sensitivity to light, sound, or smells. Other types of headaches can also cause severe pain, and not all headaches are migraines. For example, some people describe the pain of cluster headaches as the worst pain they have experienced. The exact cause of migraines is not known. Changes in neurotransmitter levels within the brain are thought to play a role.
United States Government - Independent Agencies. Independent Agencies of the Unites States government are tasked with administering the law as regarding specific areas such as the environment, social security, and veteran affairs. These Agencies are expert in the area they manage and are generally headed by a Board or Commission, while a few, such as the EPA, are headed by a single Administrator.
A government agency may be established by either a national government or a state government within a federal system. The term is not normally used for an organization created by the powers of a local government body.Agencies can be established by legislation or by executive powers.lso, most of the 50 U.S. states have created similar government agencies. The term government agency or administrative agency usually applies to one of the independent agencies of the United States government, which exercise some degree of independence from the President's control.