quadriplegia: Paralysis of all limbs, often caused by a severe neck injury.

quantitative computed tomography: A modification of computed tomography that provides measurements of bone mass as well as an image.

quarantine: A period of time in which a sick person is kept away from others to prevent the spread of disease.

quick relievers: Medications that quickly open the bronchial tubes by relaxing the muscles surrounding these airways.

quiet sleep: Any sleep other than REM sleep, in which thinking and most physiological activities slow, but movement still occurs. Also called non-REM sleep.