Sleeplessness and Circadian Rhythm Disorder Glossary of Medical Terms

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These are medical definitions of medical terms from the MedTerms.com medical dictionary that appear in the Sleeplessness and Circadian Rhythm Disorder article.

Abnormal: Not normal. Deviating from the usual structure, position, condition, or behavior. In referring to a growth, abnormal may mean that it is cancerous or premalignant (likely to become cancer ).
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Alzheimer disease: See: Alzheimer's disease .
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Ambien: Brand name for the sedative hypnotic drug zolpidem used for sleep. For more information, see: zolpidem .
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Benzodiazepines: A class of drugs that act as tranquilizers and are commonly used in the treatment of anxiety. Benzodiazepines can cause drowsiness.
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Blind: 1. Unable to see. Without part or all of the sense of sight.
2. In a clinical trial, not to know the treatment given or received. The participant is not told whether they are in the experimental or control arm of the study. Also called masked.
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Brain: That part of the central nervous system that is located within the cranium ( skull ). The brain functions as the primary receiver, organizer and distributor of information for the body. It has two (right and left) halves called "hemispheres."
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Caffeine: A stimulant found naturally in coffee beans, tea leaves, cocoa beans (chocolate) and kola nuts (cola) and added to soft drinks, foods, and medicines. A cup of coffee has 100-250 milligrams of caffeine. Black tea brewed for 4 minutes has 40-100 milligrams. Green tea has one-third as much caffeine as black tea.
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Chronic: This important term in medicine comes from the Greek chronos, time and means lasting a long time.
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Circadian: Refers to events occurring within a 24-hour period, in the span of a full (24-hour) day, as in a circadian rhythm. Circadian rhythmicity is a fundamental property possessed by all organisms. These rhythms are driven by an internal time-keeping system: a clock. Changes in the external environment, particularly in the light-dark cycle, entrain this biologic clock. Under constant environmental conditions devoid of time cues, rhythms driven by the clock show a period near, but usually not exactly equal to, 24 hours.
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Cognitive: Pertaining to cognition , the process of knowing and, more precisely, the process of being aware, knowing, thinking, learning and judging. The study of cognition touches on the fields of psychology , linguistics, computer science, neuroscience , mathematics, ethology and philosophy.
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Contrast: Short for "contrast media." Contrast media are X-ray dyes used to provide contrast, for example, between blood vessels and other tissue.
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Dysfunction: Difficult function or abnormal function.
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Endocrine: Pertaining to hormones and the glands that make and secrete them into the bloodstream through which they travel to affect distant organs. The endocrine sites include the hypothalamus, pituitary gland, pineal gland, thyroid, parathyroids, heart (which makes atrial-natriuretic peptide), the stomach and intestines, islets of Langerhans in the pancreas, the adrenal glands, the kidney (which makes renin, erythropoietin , and calcitriol), fat cells (which make leptin). the testes, the ovarian follicle ( estrogens ) and the corpus luteum in the ovary). Endocrine is as opposed to exocrine. (The exocrine glands include the salivary glands, sweat glands and glands within the gastrointestinal tract.)
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Epilepsy (seizure disorder): When nerve cells in the brain fire electrical impulses at a rate of up to four times higher than normal, this causes a sort of electrical storm in the brain, known as a seizure. A pattern of repeated seizures is referred to as epilepsy . Known causes include head injuries, brain tumors, lead poisoning, maldevelopment of the brain, genetic and infectious illnesses. But in fully half of cases, no cause can be found. Medication controls seizures for the majority of patients.
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Exacerbate: To make worse. For example, smoking may exacerbate systemic lupus erythematosus .
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Excessive daytime sleepiness: A neurological disorder in which there is a sudden recurrent uncontrollable compulsion to sleep. Excessive daytime sleepiness is also known as narcolepsy.
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Family history: The family structure and relationships within the family, including information about diseases in family members.
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Fatigue: A condition characterized by a lessened capacity for work and reduced efficiency of accomplishment, usually accompanied by a feeling of weariness and tiredness. Fatigue can be acute and come on suddenly or chronic and persist.
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FDA: The Food and Drug Administration, an agency within the U.S. Public Health Service, which is a part of the Department of Health and Human Services.
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Food and Drug Administration: The FDA, an agency within the U.S. Public Health Service, which is a part of the Department of Health and Human Services.
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Gastrointestinal: Adjective referring collectively to the stomach and small and large intestines.
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Gland: 1. A group of cells that secrete a substance for use in the body. For example, the thyroid gland. 2. A group of cells that removes materials from the circulation. For example, a lymph gland.
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Herbal: 1. An adjective, referring to herbs, as in an herbal tea.
2. A noun, usually reflecting the botanical or medicinal aspects of herbs; also a book which catalogs and illustrates herbs.
The word "herbal" was pronounced with a silent "h" on both sides of the Atlantic until the 19th century but this usage persists only on the American side.
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Hormone: A chemical substance produced in the body that controls and regulates the activity of certain cells or organs.
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Hygiene: The science of preventive medicine and the preservation of health. From the name of Hygeia, the daughter of Asklepios, the Greek god of medicine (whose staff with entwined snake is the symbol of medicine). Asklepios (known to the Romans as Aesculapius) had a number of children including not only Hygeia but also Panaceia, the patroness of clinical medicine. Hygeia also followed her father into medicine. As the patroness of health, Hygeia was charged with providing a healthy environment to prevent illness. In Greek, "hygieia" means health.
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Immune: Protected against infection. The Latin immunis means free, exempt.
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Immunosuppressive: 1. Pertaining to immunosuppression , the suppression of the immune system .
2. An agent capable of suppressing the immune response .
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Insomnia: The perception or complaint of inadequate or poor-quality sleep because of one or more of the following: difficulty falling asleep; waking up frequently during the night with difficulty returning to sleep; waking up too early in the morning; or unrefreshing sleep. Insomnia is not defined by the number of hours of sleep a person gets or how long it takes to fall asleep. Individuals vary normally in their need for, and their satisfaction with, sleep. Insomnia may cause problems during the day, such as tiredness, a lack of energy, difficulty concentrating, and irritability.
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Internal medicine: A medical specialty dedicated to the diagnosis and medical treatment of adults. A physician who specializes in internal medicine is referred to as an internist. A minimum of seven years of medical school and postgraduate training are focused on learning the prevention, diagnosis, and treatment of diseases of adults. Subspecialties of internal medicine include allergy and immunology, cardiology (heart), endocrinology (hormone disorders), hematology (blood disorders), infectious diseases, gastroenterology (diseases of the gut), nephrology (kidney diseases), oncology (cancer), pulmonology (lung disorders), and rheumatology ( arthritis and musculoskeletal disorders).
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Intervention: The act of intervening, interfering or interceding with the intent of modifying the outcome. In medicine, an intervention is usually undertaken to help treat or cure a condition. For example, early intervention may help children with autism to speak. "Acupuncture as a therapeutic intervention is widely practiced in the United States," according to the National Institutes of Health. From the Latin intervenire, to come between.
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Jet lag : A temporary disorder that causes fatigue, insomnia, and other symptoms as a result of rapid air travel across time zones.
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Medical school: A school with a curriculum leading to a medical degree. The mission of every medical school includes medical teaching, research, and patient care. All medical schools share the goal of preparing students in the art and science of medicine, and providing them with the background necessary to enter the period of graduate medical education. The years of medical school preceding graduate medical education are typically divided into a preclinical phase and a clinical phase.
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Melatonin: A hormone produced by the pineal gland, melatonin is intimately involved in regulating the sleeping and waking cycles, among other processes. Melatonin supplements are sometimes used by people who have chronic insomnia. Always see your doctor before taking melatonin, as it is not recommended for all patients with sleep problems.
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Modafinil: An oral drug first approved by the FDA in 1998 for the treatment of narcolepsy , a condition in which there is an uncontrollable desire to sleep . Modafinil promotes wakefulness. In 2004 the FDA also approved modafinil for the treatment of obstructive sleep apnea and sleeping problems caused by shift work.
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MRI: Abbreviation and nickname for magnetic resonance imaging . For more information, see: Magnetic Resonance Imaging ; Paul C. Lauterbur ; Peter Mansfield .
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Narcolepsy: A neurological disorder marked by a sudden recurrent uncontrollable compulsion to sleep . Narcolepsy is often associated with cataplexy (a sudden loss of muscle tone and paralysis of voluntary muscles associated with a strong emotion), sleep paralysis (immobility of the body that occurs in the transition from sleep to wakefulness), what are called hypnagogic hallucinations (pre-sleep dreams) and automatic behaviors (such as doing something "automatically" and not remembering afterwards how one did it).
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Neurological: Having to do with the nerves or the nervous system.
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Neurology: The medical specialty concerned with the diagnosis and treatment of disorders of the nervous system -- the brain, the spinal cord, and the nerves.
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Objective: In a microscope, the objective (also called the objective lens) is the lens nearest to the object being examined whereas the lens closest to the eye is termed the ocular (the eyepiece).
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Onset: In medicine, the first appearance of the signs or symptoms of an illness as, for example, the onset of rheumatoid arthritis . There is always an onset to a disease but never to the return to good health. The default setting is good health.
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Pacemaker: A system that sends electrical impulses to the heart in order to set the heart rhythm. The pacemaker can be the normal "natural" pacemaker of the heart or it can be an electronic device.
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Pediatric: Pertaining to children.
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Pediatrics: "Pediatrics is concerned with the health of infants, children and adolescents, their growth and development, and their opportunity to achieve full potential as adults." (Richard E.Behrman in Nelson's Textbook of Pediatrics)
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Pharmacy: A location where prescription drugs are sold. A pharmacy is, by law, constantly supervised by a licensed pharmacist.
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Pineal gland: A small gland located deep within in the brain. It is believed to secrete melatonin, and may therefore be part of the body's sleep-regulation apparatus.
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Prescription: A physician's order for the preparation and administration of a drug or device for a patient. A prescription has several parts. They include the superscription or heading with the symbol "R" or "Rx", which stands for the word recipe (meaning, in Latin, to take); the inscription, which contains the names and quantities of the ingredients; the subscription or directions for compounding the drug; and the signature which is often preceded by the sign "s" standing for signa (Latin for mark), giving the directions to be marked on the container.
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Prescription drug: A drug requiring a prescription, as opposed to an over-the-counter drug, which can be purchased without one. The word "prescription" comes from the Latin "praescriptus" compounded from "prae", before + scribere, to write = to write before. Historically, a prescription was written before the drug was prepared and administered.
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Prognosis: 1. The expected course of a disease .
2. The patient's chance of recovery.
The prognosis predicts the outcome of a disease and therefore the future for the patient . His prognosis is grim, for example, while hers is good.
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Progressive: Increasing in scope or severity. Advancing. Going forward. In medicine, a disease that is progressive is going from bad to worse.
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Provigil: Brand name of the drug modafinil. See: Modafinil .
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Psychiatry: The medical specialty concerned with the prevention, diagnosis , and treatment of mental illness.
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Pulmonology: The study and science of the anatomy , physiology , and pathology of the lungs . See also: Pulmonary medicine .
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Rebound: Return of the original symptoms when maneuvers or treatment is discontinued.
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Sensitivity: 1. In psychology, the quality of being sensitive. As, for example, sensitivity training, training in small groups to develop a sensitive awareness and understanding of oneself and of ones relationships with others. 2. In disease epidemiology, the ability of a system to detect epidemics and other changes in disease occurrence. 3. In screening for a disease, the proportion of persons with the disease who are correctly identified by a screening test. 4. In the definition of a disease, the proportion of persons with the disease who are correctly identified by defined criteria.
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Sleep : The body's rest cycle.
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Sleep disorders: Any disorder that affects, disrupts, or involves sleep . The most common sleep disorder is probably snoring, although it is usually not medically significant. Insomnia, sleep apnea , restless leg syndrome , and sleepwalking are also sleep disorders. Most large medical centers have diagnostic and treatment facilities dedicated to sleep disorders.
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Sleeplessness: Insomnia . See also Fatal familial insomnia .
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Snoring: A rough rattling noise made on inspiration during sleep by vibration of the soft palate (the back of the roof of the mouth) and the uvula (the prominent structure dangling down at the back of the mouth).
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Stress: Forces from the outside world impinging on the individual. Stress is a normal part of life that can help us learn and grow. Conversely, stress can cause us significant problems.
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Sundowning: also known as Sundown Syndrome, a term used to refer to behavioral changes that often occur in the late afternoon or evening in people with Alzheimer's disease and similar conditions. The behavioral changes make take the form of aggression, agitation, delusions, hallucinations, paranoia, increased disorientation, or wandering and pacing about. Experts are not sure why these changes occur at this time of day; possible explanations include hormonal factors, reduced vision due to lower light levels, tiredness, boredom and the absence of planned activities, or stress and anxiety of the caregiver that is communicated to the patient.
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Syndrome: A set of signs and symptoms that tend to occur together and which reflect the presence of a particular disease or an increased chance of developing a particular disease.
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Systemic: Affecting the entire body. A systemic disease such as diabetes can affect the whole body. Systemic chemotherapy employs drugs that travel through the bloodstream and reach and affect cells all over the body.
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Therapeutic: Relating to therapeutics , that part of medicine concerned specifically with the treatment of disease . The therapeutic dose of a drug is the amount needed to treat a disease.
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Therapy: The treatment of disease .
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Wrist: The proximal segment (the near part) of the hand consisting of the carpal bones and the associated soft parts.
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Zeitgeber: An environmental agent or event that provides the cue for setting or resetting a biological clock. To be synchronized with our environment , we need the input of Zeitgebers. The most important Zeitgeber in nature is light. Social factors, chemical factors and activity can also serve as Zeitgebers. Light is a so-called photic type Zeitgeber, whereas activity, for example, is called a non-photic Zeitgeber for the biological clock.
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Zolpidem: Brand name: Ambien. A sedative hypnotic drug in a class closely related the benzodiazepines, affecting the central nervous system, used as a sleep drug. For more information, see: zolpidem .
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