A - E, F - O, P - Z

forebrain: The largest division of the brain, which includes the cerebral cortex and basal ganglia. It is credited with the highest intellectual functions.

frontal lobe: One of the four divisions of each cerebral hemisphere. The frontal lobe is important for controlling movement and associating the functions of other cortical areas.

GABA (gamma-amino-butyric acid): The major inhibitory neurotransmitter in the brain.

glial cells (glia): Brain cells that support neurons by performing a variety of "housekeeping" functions in the brain.

glutamate: The most common excitatory neurotransmitter in the brain.

hallucinogens: A diverse group of drugs that alter perceptions, thoughts, and feelings. Hallucinogenic drugs include LSD, mescaline, MDMA (ecstasy), PCP, and psilocybin (magic mushrooms).

heroin: The potent, widely abused opiate that produces addiction. It consists of two morphine molecules linked together chemically.

hippocampus: A brain structure that is involved in emotions, motivation, learning, and memory.

homeostasis: The process of keeping the internal environment of the body stable by making adjustments to changes in the external environment.

hypothalamus: The part of the brain that controls many bodily functions, including feeding, drinking, and the release of many hormones.

ingestion: The act of taking food or other material into the body through the mouth.

inhalant: Any drug administered by breathing in its vapors. Inhalants commonly are organic solvents, such as glue and paint thinner, or anesthetic gases, such as ether and nitrous oxide.

inhalation: The act of administering a drug or combination of drugs by nasal or oral respiration. Also, the act of drawing air or other substances into the lungs. Nicotine in tobacco smoke enters the body by inhalation.

inhibitory neurotransmitter: A neurotransmitter that acts to prevent a neuron from firing an action potential.

injection: A method of administering a substance such as a drug into the skin, subcutaneous tissue, muscle, blood vessels, or body cavities, usually by means of a needle.

limbic system: A set of brain structures that generates our feelings, emotions, and motivations. It is also important in learning and memory.

localization of function: A principle of brain organization that states that specific places (circuits) in the brain carry out specific functions.

LSD (lysergic acid diethylamide): An hallucinogenic drug that acts on the serotonin receptor.

magnetic resonance imaging (MRI): An imaging technique that uses magnetic fields to take pictures of the structure of the brain.

marijuana: A drug, usually smoked but can be eaten, that is made from the leaves of the cannabis plant. The main psychoactive ingredient is THC.

medication: A drug that is used to treat an illness or disease according to established medical guidelines.

metabolism: The processes by which the body breaks things down or alters them so they can be eliminated.

methadone: A synthetic opiate used to treat cancer pain and heroin addiction.

methamphetamine: A commonly abused, potent stimulant drug that is part of a larger family of amphetamines.

morphine: The most potent natural opiate compound produced by the opium poppy. Morphine is a very effective medicine for treating pain.

myelin: Fatty material that surrounds and insulates axons of some neurons.

naloxone: A short-acting opiate antagonist that binds to opiate receptors and blocks them, preventing opiates from binding to these receptors.

naltrexone: An opiate antagonist used to treat heroin addiction, and more recently for the treatment of alcohol addiction.

neuron (nerve cell): A unique type of cell found in the brain and body that is specialized to process and transmit information.

neurotransmitter: A chemical produced by neurons to carry messages to other neurons.

neurotransmission: The process that occurs when a neuron releases neurotransmitters to communicate with another neuron across the synapse.

nicotine: The addictive drug in tobacco. Nicotine activates a specific type of acetylcholine receptor.

norepinephrine: A neurotransmitter and a hormone. It is released by the sympathetic nervous system onto the heart, blood vessels, and other organs, and by the adrenal gland into the bloodstream as part of the fight-or-flight response. Norepinephrine in the brain is used as a neurotransmitter in normal brain processes.

nucleus: A cluster or group of nerve cells that is dedicated to performing its own special function(s). Nuclei are found in all parts of the brain but are called cortical fields in the cerebral cortex.

nucleus accumbens: A part of the brain reward system, located in the limbic system, that processes information related to motivation and reward. Virtually all drugs of abuse act on the nucleus accumbens to reinforce drug taking.

occipital lobe: The lobe of the cerebral cortex at the back of the head that includes the visual cortex.

opiate receptors: Receptors that recognize both opiates and endogenous opioids. When activated, they slow down or inhibit the activity of neurons on which they reside.

opiates: Any of the psychoactive drugs that originate from the opium poppy or that have a chemical structure like the drugs derived from opium. Some opiates (such as opium, codeine, and morphine) are derived from the plant, while others were first synthesized by chemists.

opioid: Any chemical that has opiate-like effects; commonly used to refer to endogenous neurochemicals that activate opiate receptors.

A - E, F - O, P - Z