Which drug is known as a stimulant?

Cocaine is classified as a stimulant, which means it acts on the central nervous system to increase alertness, attention, and energy levels. Stimulants typically enhance the activity of certain neurotransmitters, such as dopamine and norepinephrine, leading to heightened feelings of euphoria and increased physical activity. The effects of cocaine can include elevated heart rate, increased blood pressure, and improved mood, all of which are characteristic of stimulant substances.

In contrast, the other substances listed are classified differently. MDMA, while sometimes considered a stimulant, is more accurately described as an empathogen or entactogen due to its effects on mood and perception combined with some stimulant properties. Heroin and morphine are opioids and are primarily depressants, meaning they slow down the central nervous system, leading to sedative effects rather than stimulation. This distinction makes cocaine the clear answer as a stimulant among the options provided.