AskDefine | Define reflex

Dictionary Definition

reflex adj : without volition or conscious control; "the automatic shrinking of the pupils of the eye in strong light"; "a reflex knee jerk"; "sneezing is reflexive" [syn: automatic, reflex(a), reflexive] n : an automatic instinctive unlearned reaction to a stimulus [syn: instinctive reflex, innate reflex, inborn reflex, unconditioned reflex, physiological reaction]

User Contributed Dictionary



from reflexus (past participle of reflectere verb)


  1. An automatic response to a simple stimulus which does not require mental processing.
  2. A corresponding phoneme in a daughter language.


automatic response


  1. bent, turned back or reflected
  2. produced automatically by a stimulus


to reflex
  1. to bend, turn back or reflect
  2. to respond to a stimulus

Extensive Definition

A reflex action is involuntary and almost instant movement in response to stimulus. In most contexts, especially involving humans, a reflex action is mediated via the reflex arc (although this is not always true in other animals, or in more casual usage of the term 'reflex'.)
Reflexes are tested as part of a neurological examination to assess damage to or functioning of the central and peripheral nervous system.
Reflexes may be trained, such as during repetition of motor actions during sport practice, or the linking of stimuli with autonomic reactions during classical conditioning.

Reaction time

For a reflex, reaction time or latency is the time from the onset of a stimulus until the organism responds.
In humans, reaction time to visual stimuli is typically 150 to 300 milliseconds.

Human reflexes

Reflex actions include:

Tendon reflexes

The deep tendon reflexes provide information on the integrity of the central and peripheral nervous system. Generally, decreased reflexes indicate a peripheral problem, and lively or exaggerated reflexes a central one.
While the reflexes above are stimulated mechanically, the term H-reflex refers to the analogous reflex stimulated electrically, and Tonic vibration reflex for those stimulated by vibration.

Reflexes involving cranial nerves

Reflexes in infants only

Newborn babies have a number of other reflexes which are not seen in adults, referred to as primitive reflexes. These include:
Processes such as breathing, digestion, and the maintenance of the heartbeat can also be regarded as reflex actions, according to some definitions of the term.


reflex in Catalan: Reacció reflexa
reflex in Czech: Reflex
reflex in Danish: Refleks
reflex in German: Reflex
reflex in Estonian: Refleks
reflex in Spanish: Reflejo
reflex in Esperanto: Reflekso
reflex in French: Réflexe (réaction motrice)
reflex in Galician: Reacción reflexa
reflex in Hebrew: רפלקס
reflex in Italian: Riflesso
reflex in Lithuanian: Refleksas
reflex in Dutch: Reflex (biologie)
reflex in Japanese: 反射 (生物学)
reflex in Norwegian: Refleks
reflex in Polish: Odruch
reflex in Portuguese: Reflexo
reflex in Romanian: Reflex
reflex in Russian: Рефлекс (биология)
reflex in Slovak: Reflex
reflex in Finnish: Refleksi
reflex in Swedish: Reflex (medicinsk term)
reflex in Turkish: Refleks
reflex in Chinese: 反射 (生理学)

Synonyms, Antonyms and Related Words

Pavlovian conditioning, action and reaction, adumbration, answer, antiphonal, arch, automatic, automatic reaction, automatic response, autonomic reaction, back, backlash, backward, backwash, behavior, bend, bend back, blind, blind impulse, bounceback, bow, brain wave, brainstorm, casual, clout, compulsive, conditioned, conditioned response, conditioning, counter, crook, curl, curve, decurve, deflect, dome, drive, echo, embow, fancy, flash, fleeting impulse, flex, force, forced, gut, gut response, hook, hump, hunch, ill-advised, ill-considered, ill-devised, impact, impress, impression, imprint, impulse, impulsive, inadvertent, incurvate, incurve, indeliberate, inflect, inspiration, instinct, instinctive, instrumental conditioning, involuntary, involuntary impulse, loop, mark, mechanical, natural impulse, negative reinforcement, notion, operant conditioning, outline, positive reinforcement, predictable response, print, psychagogy, quick hunch, reacting, reaction, reactionary, reactive, recoil, recurve, reeducation, reflect, reflection, reflex action, reflexive, refluence, refluent, reflux, reinforcement, reorientation, repercussion, reply, respondence, respondent, responding, response, responsive, retroaction, retroactionary, retroactive, retroflex, return, reverberation, reversed, revulsion, revulsive, rise, round, sag, shadow, silhouette, snap, spontaneous, sudden thought, swag, sweep, turn, turned around, unadvised, uncalculated, unconditioned reflex, unconscious, unconsidered, undeliberate, undeliberated, undesigned, unintended, unintentional, unmeditated, unpremeditated, unstudied, unthinking, unthinking response, unwilled, unwilling, unwitting, urge, vault, wind, wrong-way, wrong-way around
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