What is a reflex arc and why is it important?

A reflex arc is made up of a receptor (which detects a stimulus), a sensory neurone, a relay neurone, a motor neurone and an effector (which brings about a response). The neurones are not joined to each other, there is a small gap between them called a synapse. Impulses travel through the reflex arc and cross the synapse by means of a chemical diffusing through the gap.The reflex arc brings about a reflex action, which is a fast, automatic response to a stimulus. This is important as it helps us avoid harm or danger.