4 2) How does the brain adapt to the presence of drugs? The brain adapts to the presence of drugs by developing tolerance for the drug.Tolerance may develop because:the body may become more efficient at eliminating the chemical from the bodythe cells of the body and brain become less responsive to the effect of the drug (decrease in number of recepetors
5Dopamine D2 Receptors are Decreased by Addiction CocaineMethDA D2 Receptor AvailabilityRepeated drug exposure also changes brain function. Positron emission tomography (PET) images show similar changes in brain dopamine receptors resulting from addiction to different substances. Dopamine D2 receptors are one of five types of receptors that bind dopamine in the brain. The brain images on the left are those of controls, while those on the right are from individuals addicted to cocaine, methamphetamine, alcohol, or heroin. The striatum (which contains the reward and motor circuitry) shows up as bright red and yellow in the controls (in the left column), indicating numerous D2 receptors. Conversely, the brains of addicted individuals (in the right column) show a less intense signal, indicating lower levels of D2 receptors. This reduction likely stems from repeated over-stimulation of the dopamine receptors. Brain adaptations such as this contribute to the compulsion to abuse drugs.AlcoholHeroinControlAddicted
61) What are some of the ways that drugs cause long-term changes in the brain? The continued use of drugs may cause the brain to become resistant to the effects of the drug (tolerance).Some drugs, such as alcohol and MDMA, can kill brain cells.
7Why are large amounts of alcohol bad for the brain? In large doses, alcohol kills neurons in 2 specific brain areas:the mammillary bodies (important for memory) the cerebral cortex (controls mental functions)
121) What are some of the ways that drugs cause long-term changes in the brain? The continued use of drugs may cause the brain to become resistant to the effects of the drug (tolerance).Some drugs, such as alcohol and MDMA, can kill brain cells.Cocaine can cause the activity level of the brain to decrease for a long period of time after drug use is stopped.
13How does cocaine affect the brain? It reduces glucose metabolism up to three months after the last use of the drugThis indicates that the neurons of cocaine addicts are less active 3 months after they have stopped using the drug
153) How may the abuse of drugs relate to the plasticity of the brain? Plasticity means that the brain can modify connections (synapses) in response to experiences.Drugs that cause neuronal death can decrease the plasticity of the brain because neurons are not present to form new connections and because existing connections are lost.
174) What are some problems that scientists have when they investigate the effects of drugs on the brain?Many drug abusers abuse more than one drug.Drugs taken in combination may have different effects.Also, many drug abusers have other medical conditions
18Summary: Drugs Change Brain Chemistry! Long term drug abuse and addiction can lead to changes in the brain’s anatomy and chemistryLoss of neurons in hippocampus results in memory lossDecrease in glucose metabolism results in a reduction of the brain’s processing abilitiesThese changes in the brain cause drug addicts to loose the ability to control their drug use