Through homeostasis, the body adapts to changes in the internal and external environment. With connections to other parts of the brain, the threshold acts as a switchboard, receiving information from the limbic system, where emotions are registered, from the hypothalamus, where hormones are regulated, from the cortex, where thoughts and fears are remembered, and from the muscles of the head and neck. Alterations in the environment, such as a weather front or chemicals from the diet, are also registered in the threshold. When the circuitry becomes overloaded, the system cannot maintain equilibrium. For those with the genetic susceptibility for headache, the change in chemical balance may lead to a headache.
Cost There are direct and indirect costs associated with severe headaches.
Direct costs consist of medical-care expenditures. Indirect costs include the loss of productivity and functioning at a less than optimal level due to migraine. There are approximately 150 million work days lost every year and 329,000 school days lost per month due to migraine. In a study that compared the impact of various types of pain on absenteeism, migraine produced the most disruption at work. In addition, headache sufferers who take medication to treat the pain or to prevent headaches may have more accidents, make more errors or mistakes, and over time may experience personal problems.