Hockenbury Discovering Psychology 5th txtbk

52 CHAPTER 2 Neuroscience and BehaviorTable 2.1Summary of Important NeurotransmittersNeurotransmitter Primary Roles Associated DisordersAcetylcholine Learning, memory Alzheimer’s diseaseMuscle contractionsDopamine Movement Parkinson’s diseaseThought processesSchizophreniaRewarding sensations Drug addictionSerotonin Emotional states DepressionSleepSensory perceptionNorepinephrine Physical arousal Depression, stressLearning, memoryRegulation of sleepGABA Inhibition of brain activity Anxiety disordersEndorphins Pain perception Opiate addictionPositive emotionsBotulism: Blocking Acetylcholine forCosmetic Reasons How does Botoxeliminate facial wrinkles? Botox injectionscontain very minute amounts ofbotulinum, a toxin that causes muscleparalysis around the injection site by blockingthe release of acetylcholine from motorneurons. Because the muscles can’tcontract, the skin smoothes out, and facialwrinkles are diminished or eliminated.Produced by bacteria, botulinum toxin isextremely lethal, and can produce death ifingested in food, if inhaled, or if the toxinenters the bloodstream through brokenskin (Arnon & others, 2001). But whenpurified and properly administered ininfinitesimal amounts, botulinum toxin cansafely be used for cosmetic purposes and tohelp treat a variety of conditions, includingmigraine headaches and severe musclespasms (Montecucco & Molgó, 2005).Important NeurotransmittersAcetylcholine, the first neurotransmitter discovered, is found in all motor neurons.It stimulates muscles to contract, including the heart and stomach muscles. Whetherit is as simple as the flick of an eyelash or as complex as a back flip, all movementinvolves acetylcholine.Acetylcholine is also found in many neurons in the brain, and it is important inmemory, learning, and general intellectual functioning. People with Alzheimer’sdisease, which is characterized by progressive loss of memory and deterioration ofintellectual functioning, have a severe depletion of several neurotransmitters in thebrain, most notably acetylcholine.The neurotransmitter dopamine is involved in movement, attention, learning,and pleasurable or rewarding sensations. Evidence suggests that the addictiveness ofmany drugs, including cocaine and nicotine, is related to their ability to increasedopamine activity in the brain (Koob & Volkow, 2009; Volkow & others, 2007).The degeneration of the neurons that produce dopamine in one brain area causesParkinson’s disease, which is characterized by rigidity, muscle tremors, poor balance,and difficulty in initiating movements. Symptoms can be alleviated by a drug calledL-dopa, which converts to dopamine in the brain.Excessive brain levels of dopamine are sometimes involved in the hallucinationsand perceptual distortions that characterize the severe mental disorder called schizophrenia.Some antipsychotic drugs that relieve schizophrenic symptoms work byblocking dopamine receptors and reducing dopamine activity in the brain. Unfortunately,these antipsychotic drugs can also produce undesirable side effects. Becausethe drugs reduce dopamine in several different areas of the brain, long-term usesometimes produces symptoms that are very similar to those of Parkinson’s disease.In the chapters on psychological disorders (Chapter 13) and therapies (Chapter 14),we’ll discuss schizophrenia, dopamine,and antipsychotic drugs in more detail.The neurotransmitters serotonin andnorepinephrine are found in many differentbrain areas. Serotonin is involved inthe sleep, sensory perceptions, moods,and emotional states, including depression.Antidepressant drugs such as Prozacincrease the availability of serotonin incertain brain regions. Norepinephrine is