Fruit flies can shed light on sleep disorders in Alzheimer's patients.

The disks between the vertebrae are liable to displacement when put under strain. Heavy lifting may produce forces which cause a lumbar intervertebral disk to move out of place ("slipped disk").

Head injuries can range from a minor bump on the head to a devastating brain injury. Common causes of head injury include traffic accidents, falls, physical assault, and accidents at home, at work, outdoors, or while playing sports.

Athetosis, or constant writhing movements, is often caused by injury to deeply situated structures within the brain called the basal ganglia.

In a person with Alzheimer's disease, neurofibrillary tangles and plaques develop, causing both structural and chemical problems in the brain. Alzheimer's disease appears to disconnect areas of the brain that normally work together.

In Parkinson's disease, dopamine production becomes irregular and inadequate and nerve cells cannot properly transmit messages. This results in the loss of muscle function. By providing an even, adequate supply of medication that the body converts into dopamine, neurons are able to transmit messages and tremors improve.

In a severe impact to the head, the brain moves and hits the skull, causing injury. During a boxing match, the brain moves from side to side after the impact of a punch. Following a concussion head injury, confusion and disorientation due to temporary distortion of the brain may result.

A tension headache is pain or discomfort in the head, scalp, or neck, usually associated with muscle tightness in these areas. Tension headaches are one of the most common forms of headaches. They may occur at any age, but are most common in adults and adolescents.

Seven million Americans suffer from migraines, and 50 percent of them find no relief with available medications. This ABC News report investigates a new treatment that is showing some good results. TMS or Transcranial Magnetic Stimulation sends a magnetic pulse into the brain to disrupt the electrical storm that precedes a migraine.

A stroke may occur if an embolism travels from another part of the body and lodges within an artery in the brain. When an internal arterial wall becomes damaged, various types of emboli can form, such as one derived from platlets, thrombotic, cholesterol, or mixed. In this example, an embolism is formed in the internal carotid artery, breaks loose, travels towards the brain, and lodges in a cerebral artery. The blocked artery deprives the brain of...