A reflex arc in human physiology refers to the physiological processes involving the afferent, interneuron and efferent neurons in response to an event that requires an immediate action. A reflex arc allows a immediate action to take place prior to the afferent neurons reaching the cerebral cortex (command center).
The simplest example of a reflex arc in practice is when a person stands on a sharp thumb tack, an afferent message will be sent from the foot to the spinal cord, where an interneuron will identify that a reflex arc is required and consequently an efferent message is sent directly to the foot to move, causing the person to jump.
What is the Purpose of the Reflex Arc?
The purpose of the reflex arc is to avoid further damage to cells while the afferent messages are sent to the cerebral cortex. By producing a reflex arc the interneurons are able to initiate the immediate reflex action required.