consciousness-altering drugs
Summary
Consciousness-altering (psychoactive) drugs change awareness, mood, or perception by altering neurotransmitter activity at synapses. The MCAT sorts them into depressants, stimulants, opiates, and hallucinogens, and tests which neurotransmitter or pathway each one acts on.
Detail
Meaning: These drugs act at synapses. They can mimic a neurotransmitter (agonist), block its receptor (antagonist), or change its release or reuptake. The usual groups are:
Depressants (alcohol, barbiturates, benzodiazepines) reduce nervous system activity, largely by enhancing the inhibitory transmitter GABA. Stimulants (caffeine, nicotine, cocaine, amphetamines) raise arousal. Cocaine blocks reuptake of dopamine, norepinephrine, and serotonin, while amphetamines increase their release. Opiates (heroin, morphine) bind endorphin receptors and relieve pain. Hallucinogens (LSD, psilocybin) distort perception, and LSD and psilocybin act on serotonin receptors. Marijuana is often placed here, though some texts treat it separately.
Many drugs of abuse raise dopamine in the mesolimbic reward pathway (ventral tegmental area to nucleus accumbens), which drives reinforcement.
On the MCAT: A passage describes a drug's effect on a synapse or behavior. You classify the drug, predict the result, or link repeated use to tolerance (a larger dose is needed for the same effect), dependence, and withdrawal.
Common confusion: "Depressant" means it slows nervous system activity, not that it causes sadness. Alcohol is a depressant even though early drinking can look stimulating, because it first reduces activity in brain regions that restrain behavior.
Sources
- Psychology (Myers and DeWall)
- Discovering Psychology (Hockenbury and Hockenbury)
Written for the MCAT and checked before it was published. For study reference only. Spotted an error? Let us know.