Reflex action

Reflex action, automatic response of the human body to stimuli. If a part of the body such as the hand touches a hot object, it pulls away involuntarily, without conscious decision. Reflex action is caused by sensitive nerve endings transmitting messages to the brain which, in turn, sends a message about corrective action to the body part receiving the stimuli. Reflex action involves 4 stages—reception, conduction, transmission, and response—all occurring in a fraction of a second. Often the action is taken before pain is felt. Some types of reflex action can become “conditioned reflexes,” in which association or anticipation, rather than actual stimulus, causes a certain reaction in the body.

See also: Nervous system.