High Quality Content by WIKIPEDIA articles! A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. In most contexts, in particular those involving humans, reflex actions are mediated via the reflex arc; this is not always true in other animals, nor does it apply to casual uses of the term 'reflex'. For a reflex, reaction time or latency is the time from the onset of a stimulus until the organism responds. In animals, reaction time to visual stimuli is typically 150 to 300 milliseconds.