A reflex action is a way for the body to automatically and rapidly respond to a stimulus. It is able to work so fast because it bypasses the brain. The process is as follows:The stimulus (e.g Pressure, Temperature) is detected by a receptor which generates an electrical signal known as an impulse.This impulse is conducted by a sensory neurone towards the spinal cord where it synapses with a relay neurone. A synapse is a connection between neurones which chemicals cross to conduct an electrical impulse. The relay neurone conveys the impulse to a motor neurone which sends the impulse to the effector.The effector produces a response. For example, the effector could be a muscle in the arm which contracts to move the hand away from a hot surface.