Answer:
Alkaloids are nitrogen-based organic compounds that are commonly made from plants, which are nitrogen based. Demethyltryptamine (DMT) is a good example of an alkaloid made by plants, and is the only alkaloid naturally made by the human body. DMT has highly psychedelic properties, allowing us to dream at night and is ultimately responsible for the near-death experiences that people feel when they come close to dying.
We are carbon-based lifeforms, so when nitrogen-based compounds are introduced into our bodies, they heighten the perception of our senses and can be overwhelming depending on the alkaloid.
Some alkaloids are totally toxic and deadly, like nicotine. 50mg and you're dead.
Other alkaloids take you into la-la land, such as tryptamine.
Other alkaloids make you feel invisible and comfy, like cocaine.
Other alkaloids are so toxic that one molecule will kill you.
Many of the alkaloids that don't kill you instantly are converted by manufacturers into salts, such as hydrochlorides, after they are extracted.