Реферат: Drugs 3 Essay Research Paper DrugsDrugs are
Drugs 3 Essay, Research Paper
Drugs are 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-euphoriants, hallucinogens, and psychotropic agents.
Alcohol has always been the most widely used psychoactive substance. In most countries it is the only psychoactive drug legally available without prescription. Pleasant relaxation is commonly the desired effect, but intoxication impairs judgment and motor performance. When used chronically, alcohol can be toxic to liver and brain cells and can be physiologically addicting, producing dangerous withdrawal syndromes.
Sedative-hypnotics, such as the barbiturates and diazepam (widely known under the brand name Valium), include brain depressants, which are used medically to help people sleep (sleeping pills), and antianxiety agents, which are used to calm people without inducing sleep. Sedative-hypnotics are used illegally to produce relaxation, tranquillity, and euphoria. Overdoses of sedative-hypnotics can be fatal; all can be physiologically addicting, and some
can cause a life-threatening withdrawal syndrome. Narcotic analgesics opiates such as morphine and heroin are prescribed to produce analgesia. Because the relief of pain is one of the primary tasks of medical treatment, opiates have been among the most important and valuable drugs in medicine. Illegal use of narcotic analgesics involves injecting these substances, particularly heroin, into the veins to produce euphoria. Opiates are physiologically addicting and can produce a quite unpleasant withdrawal syndrome. Stimulant-euphoriants, such as amphetamines, are prescribed by
physicians to suppress the appetite and to treat children often diagnosed as
hyperactive. Although amphetamines stimulate adults, they have a paradoxically calming effect on certain children who have short attention spans and are hyperactive. Concaine is used medically as a local anesthetic. Amphetamines and cocaine are used illegally to produce alertness and euphoria, to prevent drowsiness, and to improve performance in physical and mental tasks such as athletic events and college examinations. Hallucinogens psychedelic drugs such as LSD, mescaline, and PCP thus far have little medical use. They are taken illegally to alter perception and thinking patterns. Marijuana is a weak hallucinogen that may be medically useful in suppressing the nausea caused by cancer treatments and possibly in reducing eye pressure in certain severe glaucomas. Psychotropic drugs have been in use since the early 1950s. Antipsychotic drugs decrease the symptoms of schizophrenia, allowing many schizophrenic patients to leave the hospital and rejoin community life. Antidepressant drugs help the majority of patients with severe depression recover from their disorder. Lithium salts eliminate or diminish the episodes of mania and depression experienced by manic-depressive patients.