Encyclopedia Health of Diseases and Disorders

Narcolepsy Definition Narcolepsy is a sleep disorder caused by the brain normal sleep/wake cycles. People with narcolepsy have sleep episodes in the daytime, hallucinations when falling asleep or awaking, and often awaken at night. ’ s inability to regulate Description Narcolepsy can affect people in any age group but may not be diagnosed for as long as ten years after onset. It can be a disabling condition. Because people with narcolepsy can fall asleep in the daytime in the middle of other activities equipment with narcolepsy can fall behind in school or be judged as lazy students even though they are of normal intelligence. Having narcolepsy does not mean that people with the disorder sleep more than other people. The disorder is better understood as a disturbance of the normal boundaries between sleeping and waking rather than simply sleeping too much. A normal adult who sleeps for about eight hours has between four and six sleep cycles during that time. A sleep cycle is a perio...

Malaria Definition Malaria is an infectious disease caused by a parasite that spends part of its life cycle in humans and part in mosquitoes. Description Malaria is a potentially fatal disease that has infected humans as far back as 50,000 Egypt in 2700 from the same period describe the symptoms of the disease. The English name of the disease comes from an eighteenth-century Italian doctor who wrote a textbook about it and attributed it to bad air, or BCE . There are records of mosquito netting being used in BCE to protect against malaria. Chinese medical records mal ’ aria in Italian. Humans develop malaria when they are infected with a protozoan called the bloodstream and are carried to the liver, where they infect liver cells and multiply. The mature parasites are released back into the bloodstream, where they infect red blood cells. The red cells burst in two to three days, releasing more parasites that, in turn, invade more red blood cells. Most of the symptoms of malaria (fev...

Lactose Intolerance Definition Lactose intolerance occurs when a person cannot digest lactose, a sugar found in milk and other dairy products. Lactose intolerance develops when lactase, an enzyme that is needed to break down milk sugar into simpler sugars, is less available or absent. Description Lactose intolerance is a very common chronic digestive disorder in which a person breaks down lactose, or milk sugar, into two simpler sugars that the body can use. A person can have a lactase deficiency without having the symptoms of lactose intolerance. Lactose intolerance is not the same as being allergic to cow An allergy to cow lactose intolerance has to do with the process of digestion. Lactose intolerance may be caused by any of three different factors. One is normal aging. As people get older, their small intestine produces lower amounts of lactase. After the lactase production drops below a certain point, the person may experience the symptoms of lactose intolerance. A second cause o...