6 Biological Bases of Behavior
STEP 4 Review the Knowledge You Need to Score High
Do you drink coffee, tea, cocoa, or cola in the morning to get you going? Lots of people do. These beverages contain a psychoactive drug called caffeine. Psychoactive drugs are chemicals that can pass through the blood-brain barrier into the brain to alter perception, thinking, behavior, and mood, producing a wide range of effects from mild relaxation or increased alertness to vivid hallucinations. The effect a person expects from a drug partly determines the effect of the drug on that person. That person may experience different effects, depending on his or her mood and social situation. Psychoactive drugs stimulate or inhibit different regions of the brain by interacting with neurotransmitter systems. Psychological dependence develops when the person has an intense desire to achieve the drugged state in spite of adverse effects. If a person uses a drug repeatedly, the intensity of effects produced by the same dose may decrease, causing the person to take larger doses. This decreasing responsivity to a drug is called tolerance. Tolerance for drugs partly depends on environmental stimuli associated with taking the drug. Physiological dependence or addiction develops when changes in brain chemistry from taking the drug necessitate taking the drug again to prevent withdrawal symptoms. Typically, withdrawal symptoms include intense craving for the drug and effects opposite to those the drug usually induces. Although hundreds of psychoactive drugs differ in their chemical composition, drugs can be classified into broad categories. One classification system categorizes drugs by their main effects: depressants, narcotics, stimulants, and hallucinogens.
• Depressants are psychoactive drugs that reduce the activity of the central nervous system and induce relaxation. Depressants include sedatives, such as barbiturates, tranquilizers, and alcohol. Among the barbiturates are secobarbital (Seconal) and phenobarbital (Luminal). Sedatives are taken to induce sleep and prevent seizures. Tranquilizers include the benzodiazepines Valium, Xanax, and Rohypnol (“roofies”), as well as quaaludes. Rohypnol has been dubbed the “date rape drug.” Tranquilizers relieve anxiety, induce sleep, and prevent seizures. Because more people use alcohol than any other depressant, alcohol has been the most studied psychoactive chemical. It acts at many sites, including the reticular formation, spinal cord, cerebellum, and cerebral cortex, and on many neurotransmitter systems. Alcohol increases transmission of the neuroinhibitor GABA, decreases transmission of the excitatory neurotransmitter acetylcholine, and increases production of beta-endorphins. In low doses, alcohol produces a relaxing effect, reduces tension, lowers inhibitions, impairs concentration, slows reflexes, impairs reaction time, and reduces coordination. It lowers inhibitions by depressing activity in the frontal lobes, which usually control expression of emotions. In medium doses, alcohol produces slurred speech, drowsiness, and altered emotions. In high doses, alcohol produces vomiting, depressed breathing, unconsciousness, coma, and even death. Chronic drinking can lead to addiction. Withdrawal symptoms include shaking (tremors), sleep problems, nausea, hallucinations, and even seizures.
• Narcotics are analgesics (pain reducers) that work by depressing the central nervous system. They can also depress the respiratory system. Narcotics include the opiates and synthetic opiates: codeine, heroin, morphine, opium, Percodan, Darvon, Talwin, Dilaudid, methadone, and Demerol. People take narcotics to induce feelings of euphoria, relieve pain, and induce sleep. Their chemical properties are very similar to the endorphins that our brains produce. Opiates are very physically and psychologically addictive.
• Stimulants are psychoactive drugs that activate motivational centers and reduce activity in inhibitory centers of the central nervous system by increasing activity of serotonin, dopamine, and norepinephrine neurotransmitter systems. Stimulants include caffeine, nicotine, amphetamines, and cocaine. Stimulants are used to treat hyperactivity and narcolepsy. Among the amphetamines are methamphetamine, benzedrine, Ritalin, ephedrine (Ephedra), and ecstasy (MDMA), made popular at “all-night raves.” Amphetamines stimulate the sympathetic nervous system and speed up the metabolism, reducing appetite and making a person feel alert, energetic, and elated. Recent research indicates that MDMA damages brain cells. Cocaine and “crack cocaine” that is sniffed, smoked, swallowed, and injected are powerfully addicting drugs that produce feelings of euphoria, excitement, and strength and reduce hunger. Various doses of cocaine can also produce neurological and behavioral problems, such as dizziness, headache, movement problems, anxiety, insomnia, depression, hallucinations, high blood pressure, and stroke. Overdose results in death; comedian John Belushi died from a cocaine/heroin overdose.
• Hallucinogens, also called psychedelics, are a diverse group of psychoactive drugs that alter moods, distort perceptions, and evoke sensory images in the absence of sensory input. Hallucinogens include lysergic acid diethylamide (LSD), phencyclidine (PCP), marijuana (THC), psilocybin from mushrooms, and mescaline (Peyote). Some users report profound, dreamlike feelings.