Reflex action is the nearly instantaneous movement in response to a stimulus. The reason why the response is instantaneous is due to the brain not being involved in the process. Instead, the nerve signals follow the reflex arc (a neural pathway that controls a reflex) to the synapse in the spinal cord. Hence, reaction times are much quicker. For instance, the average reaction time for a touch stimulus in humans is about 150 milliseconds. This means that humans can react to a touch stimulus in just under 0.15 seconds.
Though the information is processed in the spinal cord and the brain stem, information is sent still to the brain during the reflex action and the analysis of the signal is carried out, post the reaction.
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