Final answer:
Stimulants are drugs that create an excitatory condition by increasing neural activity and alertness, often by acting as agonists of the dopamine system.
Step-by-step explanation:
Drugs that create an excitatory condition within the body are known as stimulants. These are a type of psychoactive drug that stimulates the brain, leading to increased alertness, wakefulness, and neural activity. Many stimulants act as agonists of the dopamine neurotransmitter system and include substances such as cocaine, amphetamines (including methamphetamine), cathinones (e.g., bath salts), MDMA (ecstasy), nicotine, and caffeine. They affect dopamine neurotransmission, which is often associated with reward and craving, thus many of these drugs have a high potential for abuse. On the cellular level, stimulants may enhance the activity of neurotransmitters by promoting synthesis, reducing reuptake at synapses, or mimicking neurotransmitter action.