Kids Research Express

Phobia, intense and persistent fear of a specific object, situation, or activity. Because of this intense and persistent fear, the phobic person often leads a constricted life. The anxiety is typically out of proportion to the real situation, and the victim is fully aware that the fear is irrational. Behavioral techniques have proved successful in treating phobias, especially simple and social phobias. One technique, systematic desensitization, involves gradually confronting the phobic person with situations or objects that are increasingly close to the feared ones. Exposure therapy, another behavioral method, has recently been shown more effective. In this technique, phobics are repeatedly exposed to the feared situation or object so that they can see that no harm befalls them; the fear gradually fades. Antianxiety drugs have also been used as palliatives. Antidepressant drugs have also proved successful in treating some phobias.

Phenytoin or Dilantin, drug used to treat the seizures, or violent muscle contractions, caused by epilepsy. The drug can also control seizures associated with surgery of the brain or spinal cord. Phenytoin influences the movement of sodium along nerve fibers, preventing or minimizing the abnormal electrical impulses that cause seizures. Phenytoin is available by prescription in tablet, capsule, and liquid form. Taken orally, except for one liquid form made for injection, the drug is usually prescribed in 100-mg doses taken once a day. The maximum recommended daily dosage is 600 mg. To avoid stomach irritation, oral phenytoin should be taken with food. The drug’s effectiveness is usually apparent after two to three weeks of treatment. Patients with impaired liver function, diabetes, or heart disease should use this drug with caution. Although long-term use of phenytoin is common, it may be associated with the development of cancers in the lymphatic system or the bone marrow (leukemia). ...

Pelvic Inflammatory Disease (PID), bacterial infection of the upper female genital tract, including the uterus , fallopian tubes , and ovaries . PID can be caused by several different aerobic (oxygen-requiring) and anaerobic (non-oxygen-requiring) bacteria. The two most important such bacteria are Neisseria gonorrhoeae, the bacterium that causes gonorrhea, and Chlamydia trachomatis, the bacterium that causes chlamydia. These bacteria are usually transmitted through sexual intercourse with an infected partner. The usual symptoms of acute PID are fever, chills, lower abdominal and pelvic pain, and vaginal discharge or bleeding. These symptoms often begin a few days after the start of a menstrual period, particularly when Neisseria gonorrhoeae is the cause of infection. Infections due to Chlamydia trachomatis usually progress more slowly than those caused by Neisseria gonorrhoeae. On physical examination by a doctor, the uterus, ovaries, and fallopian tubes of the infected person are usu...

Paralysis, loss of voluntary movement in a part of the human body, caused by disease or injury anywhere along the motor-nerve path from the brain to the muscle fiber. Paralysis may result from injury, poisoning, infection, hemorrhage, occluded blood vessels, or tumors. Occasionally paralysis is due to congenital deficiency in motor-nerve development. Permanent paralysis results from extensive damage to nerve cells or to a nerve trunk; severely damaged nerve cells cannot regenerate. Transient or incomplete paralysis, called paresis, is often caused by infections, trauma, or poisons that temporarily suppress motor activity but do not extensively damage nerve cells. Because most of the motor nerves from either half of the brain supply the opposite side of the body, lesions in one part of the brain usually produce paralyses in the opposite half of the body. Paralysis of one limb is known as monoplegia; paralysis of two limbs on the same side of the body as hemiplegia; paralysis of both l...

Panic Disorder, mental illness in which a person experiences repeated, unexpected panic attacks and persistent anxiety about the possibility that the panic attacks will recur. A panic attack is a period of intense fear, apprehension, or discomfort. In panic disorder, the attacks usually occur without warning. Symptoms include a racing heart, shortness of breath, trembling, choking or smothering sensations, and fears of “going crazy,” losing control, or dying from a heart attack. Panic attacks may last from a few seconds to several hours. Most peak within 10 minutes and end within 20 or 30 minutes.

Pain, unpleasant sensory and emotional experience caused by real or potential injury or damage to the body or described in terms of such damage. Scientists believe that pain evolved in the animal kingdom as a valuable three-part warning system. First, it warns of injury. Second, pain protects against further injury by causing a reflexive withdrawal from the source of injury. Finally, pain leads to a period of reduced activity, enabling injuries to heal more efficiently. Pain is difficult to measure in humans because it has an emotional, or psychological component as well as a physical component. Some people express extreme discomfort from relatively small injuries, while others show little or no pain even after suffering severe injury. Sometimes pain is present even though no injury is apparent at all, or pain lingers long after an injury appears to have healed.

Osteoporosis, bone condition characterized by a decrease in mass, resulting in bones that are more porous and more easily fractured than normal bones. Fractures of the wrist, spine, and hip are most common; however, all bones can be affected. White females are the most susceptible, but other risk factors include low calcium intake; inadequate physical activity; certain drugs, such as corticosteroids, and a family history of the disease. The most common form of the disease, primary osteoporosis, includes postmenopausal (see Menopause ), or estrogen-deficient, osteoporosis (Type I), which is observed in women whose ovaries have ceased to produce the hormone estrogen; age-related osteoporosis (Type II), which affects those over the age of 70; and idiopathic osteoporosis, a rare disorder of unknown cause that affects premenopausal women and men who are middle-aged or younger. Secondary osteoporosis may be caused by bone disuse as a result of paralysis or other conditions, including weight...

Osteomyelitis, term applied to any inflammation of bone or bone marrow, usually caused by infection by such microorganisms as Staphylococcus aureus, various streptococci, Mycobacterium tuberculosis, and a host of others, as well as several fungi. The microorganisms generally reach the bone through the bloodstream from infection elsewhere. Occasionally osteomyelitis occurs by direct infection after surgery, after a compound fracture, or as a result of trauma. Osteomyelitis, especially bacterial, may occur as an acute disease. Common symptoms include chills followed by fever, with acute pain and swelling above the site of inflammation. The inflammation begins in the marrow cavity and causes softening and erosion of the long bones, often with the formation of pus-containing abscesses, and soon spreads over the entire bone, with consequent death of the hard portions of the bone. Chronic osteomyelitis, as is often seen in tuberculosis, fungus infections, or in patients with bacterial infe...

Obsessive-Compulsive Disorder, mental illness in which a person experiences recurrent, intrusive thoughts (obsessions) and feels compelled to perform certain behaviors (compulsions) again and again. Most people have experienced bizarre or inappropriate thoughts and have engaged in repetitive behaviors at times. However, people with obsessive-compulsive disorder find that their disturbing thoughts and behaviors consume large amounts of time, cause them anxiety and distress, and interfere with their ability to function at work and in social activities. Most people with this disorder recognize that their obsessions and compulsions are irrational but cannot suppress them. Treatment for obsessive-compulsive disorder includes psychotherapy, psychoactive drugs, or both. Mental health professionals consider exposure and response prevention, a type of cognitive-behavioral therapy, to be the most effective form of psychotherapy for this disorder. Medications to treat obsessive-compulsive disorde...

Obesity, medical condition characterized by storage of excess body fat. The human body naturally stores fat tissue under the skin and around organs and joints. Fat is critical for good health because it is a source of energy when the body lacks the energy necessary to sustain life processes, and it provides insulation and protection for internal organs. But the accumulation of too much fat in the body is associated with a variety of health problems. A calorie is the unit used to measure the energy value of food and the energy used by the body to maintain normal functions. When the calories from food intake equal the calories of energy the body uses, weight remains constant. But when a person consumes more calories than the body needs, the body stores those additional calories as fat, causing subsequent weight gain. Consuming about 3,500 calories more than what the body needs results in a weight gain of 0.45 kg (1 lb) of fat. Obesity can become a chronic lifelong condition caused by ove...

Neuritis, inflammation of peripheral nerves, characterized by sensory or motor disturbances that may take the form of pain (often burning), numbness, tingling (or pins-and-needles) sensations, hypersensitivity, or anesthesia, in the area supplied by the involved nerve; weakness or paralysis of the muscles innervated by the involved nerve may also take place. It is generally the result of such localized causes as injuries, pressure from arthritis involving the spine at the area where the nerve root exits, adjacent tumors, or prolonged exposure to extreme cold. Neuritis may also involve several nerves in different parts of the body. This type of neuritis usually affects the extremities. Infectious diseases, such as typhoid fever, malaria, syphilis, or tuberculosis, and diabetes, heavy-metal poisoning, alcoholism, vitamin deficiencies associated with pregnancy, beriberi, and pellagra are among the causes of certain types of neuritis.

Neuralgia, recurrent pain along the path of a sensory nerve. Neuralgia may be caused by a disorder that affects a nerve, such as tooth decay or carpal tunnel syndrome, or it may accompany such diseases as diabetes mellitus or certain vitamin deficiencies. In some cases the cause of neuralgia cannot be determined. Whatever the cause, the affected nerve does not become inflamed and its tissues are not damaged or destroyed. Trigeminal neuralgia is one of the most common forms of neuralgia, involving the trigeminal nerve, which carries sensation from the face, eyes, nose, mouth, and jaws to the brain. Trigeminal neuralgia is characterized by overwhelming sensations of stabbing pain that may be momentary or may last for minutes or hours. When it is short-lived, the condition is also known as tic douloureux. Trigeminal neuralgia may be relieved by analgesics such as aspirin, ibuprofen, and acetaminophen. In severe cases, surgery may be performed to reduce pressure on the nerve or to sever i...

Myasthenia Gravis, chronic disease marked by progressive weakness and abnormally rapid fatigue of the voluntary muscles . The muscles affected include those used in walking, breathing, chewing, and talking. A characteristic sign of the disease is drooping eyelids. Myasthenia gravis most often affects women between the ages of 20 and 30, but it can strike anyone after adolescence; after 40, it actually afflicts more men than women. Myasthenia gravis is a noninherited autoimmune disease characterized by the presence of antibodies in the blood that destroy muscle-cell sites for the reception of acetylcholine molecules. Acetylcholine normally transmits signals between nerves and muscles, so when its receptors are destroyed it cannot induce muscle contractions. No cure for the disease yet exists, but it can be treated with drugs called anticholinesterases. These drugs are capable of inhibiting an enzyme, acetylcholinesterase, that breaks down acetylcholine in the body. Myasthenia gravis m...

Muscular Dystrophy, crippling disease characterized by gradual wasting of skeletal muscle . As the disease progresses, symptoms include increased weakness and loss of muscle mass and function. Eventually a person with muscular dystrophy needs to use a wheelchair to move around. Four clinical forms of the disease are recognized, based on pattern of inheritance, age when symptoms are first noted, and distribution of the muscles earliest involved. Microscopic abnormalities of skeletal muscle are found in each type. Muscular dystrophy has its origin in a genetic mutation, but the biochemical steps by which this genetic defect manifests itself in the degenerative process in the muscle are not known. Because specific treatment is not available, general measures, including physical and occupational therapy, are used. Genetic tests for mutations in the different genes causing muscular dystrophy provide rapid and accurate diagnosis for patients.

Malnutrition, dietary condition caused by a deficiency or excess of one or more essential nutrients in the diet. Malnutrition is characterized by a wide array of health problems, including extreme weight loss, stunted growth, weakened resistance to infection, and impairment of intellect. Severe cases of malnutrition can lead to death. Deficiency diseases are usually associated with lack of vitamins or minerals. The effects of a vitamin or mineral deficiency on the body depend on the function of the particular nutrient lacking. For example, vitamin A is important for good vision, and severe deficiency of this vitamin may cause blindness. Because some vitamins and minerals have many functions, prolonged nutritional deficiencies can therefore have wide-ranging effects on health. Diets that lack a wide variety of foods may result in vitamin deficiency diseases. For example, in countries where people eat maize as the staple food and only few other foods, diets may lack niacin, a B vitami...

Ketorolac, non-steroidal anti-inflammatory drug used in the short-term management of severe, acute pain, as well as for the short-term treatment of itchy eyes caused by seasonal allergies. Ketorolac relieves pain and reduces fever and inflammation by blocking the production of prostaglandins . It is sometimes used with a narcotic to provide better pain relief than either drug alone can offer. This drug is available by prescription only as an injectable liquid, tablets and eye drops. The effectiveness of all forms is usually apparent in 30 to 60 minutes. Ketorolac should be used with caution by patients with known bleeding disorders or sensitivities to other non-steroidal anti-inflammatory drugs as well as by patients with a history of alcohol abuse, diabetes mellitus, edema, kidney or liver disease, lupus erythematosus, asthma, colitis, heart disease, or high blood pressure. The safety of this drug for pregnant or breast-feeding women or for children has not been determined. The eyedro...

Ketoprofen, drug used to reduce the inflammation, fever, and pain associated with such diseases as arthritis, bursitis, tendinitis, and menstrual cramps. Ketoprofen is believed to work by preventing prostaglandins (chemicals that cause inflammation and contribute to the brain’s perception of pain) from concentrating in body tissues. Ketoprofen is available by prescription in capsule, tablet, and suppository form. The drug is taken daily in 3 or 4 doses for a total of 150 to 300 mg. It is most effectively absorbed if taken on an empty stomach, but it can be taken with food, milk, or an antacid to prevent stomach irritation. The patient must take ketoprofen for one to three weeks before physicians can evaluate its effectiveness. Possible side effects include drowsiness, fluid retention, skin rash, headache, depression, indigestion, and nausea. Men may experience problems with sexual performance and breast enlargement. Women may find their menstrual cycles affected, with increased blood ...

Ketoconazole, prescription drug used to treat fungal infections. It works by weakening fungal cell walls, thereby either killing the fungus or stopping its growth. Ketoconazole is also used to treat prostate cancer because it suppresses the production of testosterone, a hormone necessary for prostate cancer cell survival. Ketoconazole is available as a tablet, cream, or shampoo. Patients using the drug in tablet form take 200 to 400 mg once a day for fungal infections and 400 mg three times a day for prostate cancer. The drug should be taken with food for better absorption and to avoid stomach irritation. It must be taken for two to four weeks before a physician can evaluate its effectiveness as an antifungal agent. A cure may require many months of treatment. Common side effects of ketoconazole include reduced testosterone production (which may impair sexual function in males), skin irritation and rash, headache, nausea, diarrhea, and liver problems. Pregnant and nursing women, patien...

Irritable Bowel Syndrome (IBS), also known as spastic colon, recurring symptoms of constipation , diarrhea , and abdominal cramping that appear without a clear cause The diarrhea associated with IBS is not true diarrhea in that there is no increase in stool volume. Patients sometimes pass mucus with the stools and have a sensation of incomplete evacuation of the bowels following defecation. Recurring IBS has been associated with stress, although abdominal distress is a common reaction to anxiety in many people who do not suffer from IBS. Physicians diagnose IBS only after conducting a series of tests that rule out other gastrointestinal disorders, such as inflammatory bowel disease, intestinal parasites, and polyps. These tests include a barium enema, stool parasite culture, and sigmoidoscopy, examination of the lower intestines with a hollow, tubelike instrument passed through the anus. There is no cure for IBS and treatment focuses on alleviating symptoms. High fiber diets or antispa...

Influenza, also known as flu, contagious infection primarily of the respiratory tract. Influenza is sometimes referred to as grippe. Influenza is caused by a virus transmitted from one person to another in droplets coughed or sneezed into the air. It is characterized by coldlike symptoms plus chills, fever, headaches, muscle aches, and fatigue. Most people recover completely in about a week. But some people are vulnerable to complications such as bronchitis and pneumonia. This group includes children with asthma , people with heart or lung disease, and the elderly. Influenza is an acute disease with a rapid onset and pronounced symptoms. After the influenza virus invades a person’s body, an incubation period of one to two days passes before symptoms appear. Classic symptoms include sore throat, dry cough, stuffed or runny nose, chills, fever with temperatures as high as 39º C (103º F), aching muscles and joints, headache, loss of appetite, occasional nausea and vomiting, and fatigue. F...

Impetigo, contagious skin disease, which commonly appears in young children and infants, although adults may be affected. Usually caused by group A streptococci or by staphylococci, it appears on such exposed parts of the skin as the face, hands, arms, and legs and is spread to adjacent areas by scratching. It also spreads readily to other people by direct contact or by contact with articles used by the infected person. The infection produces pus -filled blisters that rupture and harden to form yellow crusts, from which fluid may ooze. Treatment consists of removing the crusts with soap and water and applying ointments containing antibiotics. When treated promptly, impetigo usually heals within a week without leaving scars.

Hypothermia, condition in which body temperature falls drastically as a result of exposure to cold. It may occur, for example, in hikers caught in a sudden cold front without sufficient clothing. The elderly can die from hypothermia at temperatures that would not harm younger persons. The condition involves a paradoxical response to sudden cold: the shutting off of blood flow to the body's surface. First aid may involve wrapping the victim in blankets (along with the rescuer, if necessary). Despite customary belief, alcohol causes loss of heat and should not be given. Treatment at a hospital involves slowly raising the body temperature by various means. Hypothermia may also be induced for medical purposes. Reduction in body temperature causes a slowing of the metabolism . This is useful in certain types of surgery and to reduce bleeding in a particular part of the body.

Hodgkin’s Disease or Hodgkin's Lymphoma, less severe form of two types of cancer that arise in the lymphatic system (network of small vessels that carry lymph, a fluid containing white blood cells of the immune system ). The other form is non-Hodgkin's lymphoma. Hodgkin's disease is characterized by usually painless but progressive enlargement of lymph nodes (or glands) and other lymphoid tissue. Diagnosis of Hodgkin's disease is made with a biopsy (removal of a small tissue sample for examination under a microscope). Hodgkin's disease is primarily distinguished from non-Hodgkin's lymphoma by the presence of Reed-Sternberg cells, large cells that contain several nuclei. If the disease is diagnosed at an early stage and has not metastasized (spread to other areas of the body), radiation therapy is commonly used. With advanced cases, the doctor will usually prescribe chemotherapy (anti-cancer drugs) for approximately six months, often in combination with radiation...

Heparin, substance produced by cells of the liver, lungs, and intestines that keeps blood from clotting. It normally inhibits the clotting of blood by interfering with the production of thrombin, an enzyme necessary for clot formation. Heparin obtained from animals is administered after surgery to reduce the risk of thrombosis, the formation of a blood clot in a blood vessel. It is also used after pulmonary embolism to ensure that no further clots form, as well as during kidney dialysis.

Ulcer, shallow sore produced by the destruction of skin or mucous membrane. Skin ulcers may occur in association with a number of chronic illnesses, such as diabetes, kidney and heart ailments, varicose veins , syphilis , leprosy , tuberculosis , and cancer . Gastrointestinal ulcers occur with chronic gastritis , ulcerative colitis, and typhoid fever . Peptic ulcers are ulcers of the stomach (gastric) or small intestine (duodenal). In addition to the pain caused by the ulcer itself, peptic ulcers give rise to such complications as hemorrhage from the erosion of a major blood vessel; perforation of the wall of the stomach or intestine, with resultant peritonitis ; or obstruction of the gastrointestinal tract because of spasm or swelling in the area of the ulcer. The direct cause of peptic ulcers is the destruction of the gastric or intestinal mucosal lining by hydrochloric acid, an acid normally present in the digestive juices of the stomach . Infection with the bacterium Helicobact...

Hemorrhage, excessive discharge of blood from blood vessels, caused by pathological condition of the vessels or by traumatic rupture of one or more vessels. Hemorrhage is a complication of many diseases. Peptic ulcer , for example, may cause hemorrhage by eroding a blood vessel. Stroke is sometimes due to hemorrhage in the brain. Hemophilia , a hereditary blood disease, is characterized by failure of the blood to coagulate. Sudden loss of more than about 1 liter (1 qt) of blood may lead to shock ; unless the blood is replaced by transfusion, this shock can be fatal. Bleeding normally stops through the process of coagulation, or clotting of the blood, and methods used to stop hemorrhage depend on stanching the flow of blood sufficiently for a clot to form. The hemorrhage is most effectively stopped by the application of pressure directly over the wound. Bleeding is also lessened by placing the body so that the wound is uppermost. A tourniquet should never be applied if there is another ...

Heartburn, condition characterized by a burning feeling in the chest and a sour or bitter taste in the mouth. Heartburn typically develops when the acidic contents of the stomach flow back, or regurgitate, into the esophagus, the muscular tube that carries food from the throat to the stomach. Heartburn is generally diagnosed with a complete description of the symptoms. In severe cases, a physician may order a barium X ray of the stomach and esophagus to rule out other problems. Alternatively, a physician may examine the esophagus with an endoscope, an instrument that can view the interior of the digestive tract, and take tissue and fluid samples. Treatments for heartburn in mild cases, over-the-counter medications such as antacids can relieve occasional bouts. Chronic heartburn can be treated with medications that prevent the production of acid in the stomach. Lifestyle changes, such as quitting smoking or losing weight, also can alleviate or prevent heartburn. Sleeping with the head o...

Pravastatin, drug used to lower cholesterol levels in the bloodstream in cases when dietary changes, weight loss, and exercise are ineffective in lowering cholesterol. Pravastatin works by blocking the liver enzyme that controls the manufacture of cholesterol. It is primarily effective against low-density lipoproteins (LDL), the form of cholesterol associated with increased risk of heart disease. Available only by prescription, tablets of pravastatin are taken with or without food, usually at bedtime. The typical dosage ranges between 10 and 40 mg per day. Typically, cholesterol levels begin falling four to six weeks after the medication is started. Pravastatin is often prescribed in combination with a cholesterol-lowering diet. Pregnant or nursing women, or children under the age of 18, should not take pravastatin. Patients with liver or kidney disease, muscular disorders, cataracts, or a history of alcohol abuse should use this drug with caution. Pravastatin can cause damage to the ...

Simvastatin, drug used to lower cholesterol levels. It is typically prescribed by a physician when dietary changes, weight loss, and exercise are not effective in reducing cholesterol. Simvastatin works by blocking the liver enzyme that controls the production of cholesterol. It is primarily effective against low-density lipoproteins (LDL), the form of cholesterol associated with increased risk of coronary heart disease. Tablets are taken with or without food, usually at bedtime. The typical dosage ranges between 5 and 40 mg per day. Effectiveness is usually apparent after four to six weeks of treatment. Simvastatin is usually prescribed in combination with a cholesterol-lowering diet. This drug should not be taken by patients with liver disease, by pregnant or nursing women, or by young people under the age of 20. Patients with impaired liver function, muscular disorders, cataracts, or a history of alcohol abuse should use this drug with caution. Possible side effects of this drug in...

Lovastatin, drug used to reduce high blood cholesterol levels and slow the progression of coronary atherosclerosis, or hardening of the heart’s arteries. Lovastatin interferes with an enzyme in the liver responsible for making cholesterol , a fatlike substance that can both harden and clog the arteries. This drug reduces low-density lipoproteins (LDL), the type of cholesterol that increases the risk of coronary heart disease, and increases high-density lipoproteins (HDL), the type of cholesterol thought to reduce the risk of heart disease. Available by prescription only, this drug is dispensed in 10-mg, 20-mg, and 40-mg tablets, which are taken orally. The initial adult dosage is 20 mg taken once a day, after which the dosage may be increased up to 40 mg twice a day. The maximum dosage should not exceed 80 mg daily. Effectiveness should be apparent within two weeks. This drug should be taken with food, preferably with evening meals. It should not be used by persons who have had an alle...

Coronary heart disease, the most common type of heart disease caused by atherosclerosis, the buildup of fatty material called plaque on the inside of the coronary arteries (see Arteriosclerosis ). Over the course of many years, this plaque narrows the arteries so that less blood can flow through them and less oxygen reaches the heart muscle. The most common symptom of coronary heart disease is angina pectoris , a squeezing chest pain that may radiate to the neck, jaw, back, and left arm. Angina pectoris is a signal that blood flow to the heart muscle falls short when extra work is required from the heart muscle. An attack of angina is typically triggered by exercise or other physical exertion, or by strong emotions. Coronary heart disease can also lead to a heart attack, which usually develops when a blood clot forms at the site of a plaque and severely reduces or completely stops the flow of blood to a part of the heart. In a heart attack, also known as myocardial infarction, part of ...

Gingivitis, painless inflammation or degeneration of the gum tissue, or gingiva, considered the first stage of gum disease. The gum tissue between the teeth becomes swollen and uneven; the tissue at the gum line becomes darker; and gums bleed easily. In advanced cases, the mouth will develop a noticeably unpleasant odor. Gingivitis is caused by the buildup of plaque, a film of bacteria that sticks to the teeth at the gum line. Toxins released from the bacteria irritate the gums, causing the gums to swell and bleed. This enables the bacteria to penetrate just below the gum line into an area known as the gingival sulcus. Warm, moist, and protected from the tongue and the chewing movement of the teeth, the gingival sulcus provides the perfect environment for bacteria to breed. Moreover, the delicate tissues of the sulcus are particularly vulnerable to the strong toxins produced by the bacteria. As the bacteria grow and continue to release toxins, they create a solid pocket of plaque ben...

Spasm, involuntary and abnormal violent contraction of muscles or muscle tissue. Tonic spasm, or cramp, is characterized by an unusually prolonged and strong muscular contraction, with relaxation taking place slowly. The extreme example of tonic spasm is tetanus , in which the spasms are so violent and so enduring that they may paralyze breathing. In the other form of spasm, called clonic spasm, contractions of the affected muscles take place repeatedly, forcibly, and in quick succession, with equally sudden and frequent relaxations. The most typical examples of clonic spasm are epilepsy and convulsive hysteria. The medicines used to counteract spasmodic muscular activity are termed antispasmodics. These are used in certain surgical procedures because they block transmission of nervous impulses to the muscles. Derivatives of hemlock and some 50 other plants have a relaxing effect on muscles.

Emphysema, progressive respiratory disease characterized by coughing, shortness of breath, and wheezing, developing into extreme difficulty in breathing, and sometimes resulting in disability and death. Although the exact cause is unknown, bronchial spasm , infection , irritation, or a combination of the three seem to be contributory. The highest degree of occurrence is among heavy cigarette smokers, especially those exposed to polluted air. Children who suffer from bronchitis or asthma are also susceptible. In the course of the disease the passages leading to the air sacs of the lungs become narrowed. Air is trapped in the sacs, and the tissues of the lungs lose their natural elasticity and undergo destructive changes. Symptoms akin to the common cold or asthmatic wheezing may result. As the disease progresses the volume of residual air trapped in the lungs increases, and the volume of each breath decreases. The lungs increase in size, and in severe cases the patient develops a ch...

Elephantiasis, disease of the lymphatic system , characterized by an enormous enlargement of the infected area. The hardened skin of this area resembles the hide of an elephant. The disease is usually the result of blockage of the lymphatic system by threadlike filarial worms, usually Wuchereria bancrofti. The parts of the body most frequently affected are the limbs and the genitals. The disease is treated with the antifilarial drug diethylcarbamazine (Hetrazan) and with surgery .

Dysentery, acute or chronic disease of the large intestine of humans, characterized by frequent passage of small, watery stools, often containing blood and mucus, accompanied by severe abdominal cramps. Ulceration of the walls of the intestine may occur. Although many severe cases of diarrhea have been called dysentery, the word properly refers to a disease caused by either a specific amoeba, Entamoeba histolytica, or a bacillus that infects the colon. Amoebic dysentery, caused by the parasite Entamoeba histolytica, is endemic in many tropical countries, but is attributable more to unsanitary conditions than to heat. It is most commonly spread by water or contaminated, uncooked food or from carriers. Flies may carry the cysts to spread the amoeba from the feces of infected persons to food. Various drugs, including metronidazole, ementine, and iodine-containing preparations, have been useful in treating severe cases of the disease. Bacillary dysentery is caused by certain nonmotile bact...

Drowning, death by suffocation due to the presence of water in the respiratory system. Resuscitation by artificial respiration can prevent the death of a person with water in the lungs if instituted quickly. Because of the constant need of body tissues for oxygen, even a few minutes of suffocation can result in brain damage or death. The exception to this appears in persons who have been submerged in cold water. Some victims have been completely revived, without brain damage, after having been underwater for as long as a half hour. This phenomenon, the so-called diving reflex, has long been observed in sea mammals. Activated when the face is plunged into water below 21° C (70° F), it slows body processes so that oxygen-bearing blood is diverted to the heart and brain.

Doxycycline, antibiotic drug used to treat various types of bacterial infections including urinary tract infections, traveler’s diarrhea, Rocky Mountain spotted fever, trachoma , and syphilis. It is also sometimes used to treat early Lyme disease and to prevent the spread of malaria. Doxycycline belongs to a group of antibiotics known as tetracyclines. It works by interfering with the invading bacteria’s ability to form essential proteins, thereby halting their growth. This drug is available by prescription in capsules, tablets, and liquid forms, which are taken orally, although one form of liquid is made for injection. Typical dosages range from 100 to 200 mg per day, taken in one or two doses, with a recommended maximum dose of 300 mg a day. Unless this drug causes stomach upset, it should be taken on an empty stomach (one hour before or two hours after a meal) with a full glass of water. Doxycycline usually relieves symptoms after 48 hours of treatment, but it should be taken for t...

Psychoactive Drugs, chemical substances that alter mood, behavior, perception, or mental functioning. Throughout history, many cultures have found ways to alter consciousness through the ingestion of substances. In current professional practice, psychoactive substances known as psychotropic drugs have been developed to treat patients with severe mental illness. Psychoactive substances exert their effects by modifying biochemical or physiological processes in the brain. The message system of nerve cells, or neurons, relies on both electrical and chemical transmission. Neurons rarely touch each other; the microscopic gap between one neuron and the next, called the synapse, is bridged by chemicals called neuroregulators, or neurotransmitters. Psychoactive drugs act by altering neurotransmitter function. The drugs can be divided into six major pharmacological classes based on their desired behavioral or psychological effect: alcohol, sedative-hypnotics, narcotic analgesics, stimulant-eupho...

Lysergic Acid Diethylamide (LSD), potent hallucinogenic drug, also called a psychedelic (see Psychoactive Drugs ), first synthesized from lysergic acid in Switzerland in 1938. Lysergic acid is a component of the mold of ergot, a fungus that forms on rye grain. The drug evokes dreamlike changes in mood and thought and alters the perception of time and space. It can also create a feeling of lack of self-control and extreme terror. Physical effects include drowsiness, dizziness, dilated pupils, numbness and tingling, weakness, tremors, and nausea. Transient abnormal thinking induced by LSD, such as a sense of omnipotence or a state of acute paranoia, can result in dangerous behavior. Long-term adverse reactions such as persistent psychosis, prolonged depression, or faulty judgment have also been reported following LSD ingestion, but whether these are a direct result of ingestion is difficult to establish. Physiologically, LSD may cause chromosomal damage to white blood cells; no hard evid...

Cyst, in medicine , encapsulated sac, having no opening, and enclosing liquid or semisolid pathological or foreign material. The cyst wall, formed of fibrous connective tissue or of muscular fibers, has an inner surface lined with epithelium . Retention cysts arising from distension of preexisting spaces result from the closure of a duct such as that of a sebaceous gland. An effusion of blood into a body cavity may result in an exudation cyst. Dermoid cysts are due to faulty development during the embryonic period. Adventitious cysts develop around foreign bodies or parasites introduced into deep tissue . When an inert body such as a metal or glass splinter is embedded in muscle tissue, it may become encysted. Another type of adventitious cyst is formed by the larvae of certain parasitic worms. Treatment of cysts is by surgical removal of the entire sac.

Crohn’s Disease, sometimes called regional enteritis, a chronic inflammation of the intestines resulting from an extreme reaction of the immune system . The cause is unknown, although there is a genetic tendency to develop this disease and environmental factors are also thought to play a part. It may occur at any age but is most common in young adults, with most people first affected during their teens or twenties. The symptoms of Crohn's disease include diarrhea, abdominal pain, weight loss, and fever. Anemia is also common due to bleeding from the intestine but such hemorrhaging is rare. The lining of the intestine becomes inflamed and ulcers form. Parts of the lining also become swollen, forming a characteristic “cobble-stoned” appearance. The muscle wall of the intestine becomes toughened and fibrous and some areas may become obstructed. Abnormal passages, called fistulae, may form when the inflammation spreads from the intestine through its wall and makes a hole, allowing part...

Colorectal Cancer, malignancy of the large intestine , the lower portion of the intestinal tract, which consists of the colon and rectum. Although colon cancer can occur in any segment of the colon, it is most common in the sigmoid colon, the section closest to the rectum. Two simple tests can detect most colorectal tumors while they are still in an early, easy-to-treat stage. The first test is the digital rectal examination, during which the physician uses a gloved finger to gently check the smoothness of the rectal lining. The second test is the fecal occult blood test, in which a small sample of the patient’s feces is smeared on a card coated with a chemical called guaiac, which reacts with blood. The card is analyzed in a laboratory for occult (hidden) blood. A positive result does not necessarily indicate the presence of cancer. Although most colorectal cancers bleed, so do benign conditions such as hemorrhoids. Another test is fiberoptic sigmoidoscopy, in which a flexible instrum...

Bulimia, an eating disorder in which persistent overconcern with body weight and shape leads to repeated episodes of binging (consuming large amounts of food in a short time) associated with induced vomiting, use of laxatives, fasting, and/or excessive exercise to control weight. Sometimes bulimic behavior is observed in cases of anorexia nervosa , or abnormal dieting, but bulimia in itself does not result in severe weight loss. It can, however, cause gastrointestinal problems and serious potassium depletion, and teeth may be damaged due to the acid nature of the regurgitated food. Bulimia usually develops during adolescence (most commonly among females) as a result of various psychological pressures, the most obvious one being the social emphasis on the desirability of slimness. Various modes of group and behavioral therapy are used in treating the disorder. Because patients with bulimia often suffer from depression as well, antidepressant drugs may be effective

Carcinoma, cancer that develops in the inner and outer surfaces of the body, such as the skin, the lining of the gastrointestinal tract, the inside of blood vessels, and the lungs. Like all cancers, carcinomas are malignant tumors in which cells grow uncontrollably, eventually crowding out normal cells. Also, like other cancers, carcinomas often spread to other areas of the body or metastasize via the blood or lymphatic system. Different kinds of carcinomas include breast cancer, cervical cancer, prostate cancer, lung cancer, colon cancer, liver cancer, and skin cancer. Carcinoma is one of four types of cancer. The other types are cancer in muscle, connective, or bone tissue (sarcoma), cancer in blood forming, or vascular, tissues (lymphoma, leukemia , and myeloma), and cancer in nerve tissues (neuroma, glioma, and neuroblastoma). Diagnostic techniques include endoscopy , pap test, blood tests, biopsy, and imaging techniques such as X rays, CT scans (X rays that give a three-dimensi...

Breast Cancer, malignant tumor in the glandular tissues of the breast . Such tumors, also called carcinomas , form when the processes that control normal cell growth break down, enabling a single abnormal cell to multiply at a rapid rate. Carcinomas, which tend to destroy an increasing proportion of normal breast tissue over time, may spread, or metastasize, to other parts of the body. Scientists do not understand exactly what causes breast cancer. Studies suggest that several categories of women are at increased risk for the disease: those with a long menstrual history (menstrual periods that started before age 12 and ended after age 50); those who never gave birth or who waited until after age 30 to have children; and those who have used birth control pills or hormone replacement therapy. Such risk factors, all of which relate to hormone-based life events, suggest that breast cancer is somehow affected by prolonged exposure to female sex hormones, such as estrogen . X-ray examinati...

Biopsy, surgical removal of living body tissue for study and diagnosis with a microscope . Biopsies are performed on organs to analyze the cause and nature of disease, and on tumors, or abnormal tissue growths, to determine if they are a type of cancer . For patients diagnosed with certain diseases, follow-up biopsies are used to study the effectiveness of a chosen course of medical treatment. Biopsies are vital in diagnosing and monitoring a wide range of illnesses, including muscular dystrophy, characterized by gradual wasting away of skeletal muscle, and Crohn’s disease , the chronic inflammation of the intestines. An external biopsy specimen is taken by cutting or scraping a piece of tissue from an affected area of skin . When a sample is needed from an area well below the surface of the skin, the procedure is called internal biopsy, and viewing techniques such as ultrasound or computer axial tomography are often used to help the physician guide a hollow needle to the exact locati...

Beriberi, diet-deficiency disease caused by a lack of vitamin B1. Chronic deficiency is known to cause two distinct forms of beriberi. When associated with low calorie intake and inactivity, the disease tends to affect the nervous system . This form, termed dry beriberi, is characterized by neuritis in the lower extremities, often with muscle atrophy, poor coordination, and eventually paralysis . The second form of beriberi, known as wet beriberi, is usually associated with extremely high activity levels and a high carbohydrate intake. Symptoms of wet beriberi include sweating, warm skin, and elevated heart rate; heart failure and death may follow. Beriberi is especially prevalent in those parts of the world where the diet consists mainly of polished rice. Recovery is complete in about 50 percent of cases when adequate amounts of vitamin B1 are restored to the diet.

Anorexia Nervosa, mental illness in which a person has an intense fear of gaining weight and a distorted perception of their weight and body shape. People with this illness believe themselves to be fat even when their weight is so low that their health is in danger. A person with anorexia nervosa severely restricts food intake and usually becomes extremely thin. People with anorexia nervosa—who are sometimes known as anorectics or anorexics—have a preoccupation with food, weight, dieting, and body image. They are dissatisfied with their bodies, perceive themselves to be fat regardless of their actual weight, and are obsessed with becoming thin. Many are so focused on outward appearance that they have little awareness of internal sensations such as hunger and fullness. Anorexics usually undertake strict diets, severely restricting food intake and avoiding certain foods they deem taboo. They may also undergo intense, strenuous exercise regimens and weigh themselves frequently.

Addiction, habitual repetition of excessive behavior that a person is unable or unwilling to stop, despite its harmful consequences. People can be physically addicted to a drug, meaning they may suffer ill physical effects if they stop taking the drug. They also can be psychologically addicted to drugs, gambling, or other behaviors, meaning they feel overwhelmingly deprived if they attempt to stop.