too, have nAChRs that can be overstimulated by nicotine. In humans,
nicotine poisoning produces disruptions in heart rhythm, blood pres-
sure, and respiration.
Alcohol and the sedative-hypnotic drugs. Used in the context of human
consumption, alcohol refers to the two-carbon ethyl alcohol or
ethanol. All organic alcohols are poisons, but ethanol appears to be
the least poisonous to the human body. Ethanol in alcohol-containing
beverages is formed by the metabolic action of yeast on sugars coming
from various plant materials. The yeasts consume the sugars—a bio-
chemical process called fermentation—and excrete ethanol as a waste
product. A piece of fruit sitting around will ferment from the action
of wild yeasts that settle upon it. And because yeasts are living all over
the place, humans probably serendipitously discovered the intoxicat-
ing properties of alcohol a very long time ago.
Ethanol is a member of a larger class of drugs known as sedative-
hypnotics, so named because in low doses they produce sedative or re-
laxing effects and in higher doses they produce a hypnotic or sleep-in-
ducing effect. This spectrum of effects for alcohol and other sedative-
hypnotics is well known: from the relaxation of mild intoxication, to
impaired judgment and coordination, to grossly impaired movement,
to loss of consciousness (passing out), to death. Along the way, people
may also experience what is called a blackout—loss of memory with-
out loss of consciousness (see Chapter 19).
While ethyl alcohol may be the most ancient and widely used of the
sedative-hypnotic drugs, there are many other representatives of this
category, mostly from the world of pharmaceuticals—synthetic drugs
manufactured and sold for medical use. Among these are the barbi-
turates, first introduced into medicine in the early twentieth century
and for many decades widely prescribed by physicians to treat anxi-