Final answer:
Amphetamine acts as an agonist to increase dopamine activity in the brain, alcohol enhances the inhibitory effects of GABA, and opiates like heroin act as agonists to increase the release of endogenous opioids.
Step-by-step explanation:
Amphetamine, alcohol, and opiates like heroin all work by affecting brain chemistry and altering the activity of neurotransmitters in the synapse.
Amphetamine acts as an agonist, increasing the activity of dopamine neurotransmitters in the brain. It does this by promoting dopamine synthesis, reducing its reuptake, and mimicking its action by binding to dopamine receptors.
Alcohol, on the other hand, acts as a depressant and enhances the inhibitory effects of the neurotransmitter GABA. It increases GABA activity, leading to sedation and relaxation.
Opiates like heroin bind to opioid receptors in the brain and act as agonists, increasing the release of endogenous opioids. This leads to pain relief, euphoria, and a sense of well-being.