A drug that causes hallucinations (profound distortions in a person’s perceptions of reality). Under the influence of hallucinogens, people see images, hear sounds, and feel sensations that seem real but do not exist. Some hallucinogens also produce rapid, intense emotional swings. Hallucinogens cause their effects by disrupting the interaction of nerve cells and the neurotransmitter serotonin. Distributed throughout the brain and spinal cord, the serotonin system is involved in the control of behavioral, perceptual, and regulatory systems, including mood, hunger, body temperature, sexual behavior, muscle control, and sensory perception.
LSD (an abbreviation of the German words for “lysergic acid diethylamide”) is the drug most commonly identified with the term “hallucinogen” and the most widely used in this class of drugs. It is considered the typical hallucinogen, and the characteristics of its action and effects apply to the other hallucinogens, including mescaline, psilocybin, and ibogaine.
A drug that induces hallucinations. (This is incorrect usage; the noun is hallucinogen.)
- Hallux valgus
A condition in which the big toe (hallux) is bent outward (toward the midline of the foot; valgus) so that it overlaps the second toe. Hallux valgus may be accompanied by a bunion (localized painful swelling) and is frequently associated with inflammation. It can be related to inflammation of the nearby bursa (bursitis) or degenerative […]
- Hallux varus
A condition in which the joint of the big toe is bent inward (away from the midline of the foot; varus).
A benign (noncancerous) tumor-like growth consisting of a disorganized mixture of cells and tissues normally found in the area of the body where the growth occurs.
- Hamartoma, hypothalamic
A benign tumor of the hypothalamus, the area of the brain that controls body temperature, hunger, and thirst. (In technical terms, the hypothalamus lies beneath a structure known as the thalamus and forms the floor of the third ventricle of the brain.) A small hypothalamic hamartoma can cause the patient to feel as though they […]