by Lisa Frederiksen
The following provides a brief overview of the effects on the brain of alcohol, marijuana and cocaine. The image of the ’3-Brain’ Brain Complex helps one see where these brain impacts
Image Courtesy: Jessica Scott
are occurring and which neural network activities are being effected.
Cocaine. When someone snorts, injects, or smokes cocaine, it travels to the brain very quickly. It reaches all areas of the brain but has its greatest effects in the front part of the cerebral cortex and on part of the limbic system.
A very complicated process takes place in the brain after it is exposed to cocaine. In a normal brain, the neurotransmitter dopamine is released by neurons to carry messages in the limbic system. After the message has been carried to the next neuron, dopamine is reabsorbed from the synapse back into the neuron that released it. Cocaine blocks the reabsorption of dopamine, leaving too much dopamine in the synapse. The excess dopamine is what causes the pleasurable feelings associated with taking cocaine and the increased motor activity seen with higher doses.
After a person abuses cocaine for a while, the brain tries to compensate for the excess dopamine, and the normal processes that take place are disrupted. The brain will no longer function normally without cocaine.
Marijuana. The active ingredient in marijuana that produces changes in brain messages is called tetrahydrocannabinol (THC). The brain has receptors for a specific chemical, anandamide, which is naturally produced by the brain. THC is able to attach to and activate these same receptors. When a person uses marijuana, the chemicals in the drug travel through the bloodstream and attach to the THC receptors, activating them and interfering with normal neurotransmission.
The areas of the brain with the most THC receptors are the cerebellum, the cerebral cortex, and the limbic system. This is why marijuana affects thinking, problem solving, sensory perception, movement, balance, and memory.
Alcohol. The parts of the brain affected by alcohol are the cerebral cortex, limbic system, and brain stem [Cerebellum]. Alcohol interferes with messages carried by many neurotransmitters in the brain. Because these neurotransmitters are found throughout the brain, alcohol affects many functions, including thinking, coordination, and emotions.
Source: NIDA, “How Drugs Affect the Brain,” National Institute on Drug Abuse (NIDA) of the National Institutes of Health (NIH), last updated 9/19/08, <http://www.drugabuse.gov/JSP/MOD6/page3.html>
