A reflex arc is the pathway by which a reflex travels, which at its simplest includes a sensory nerve and a motor nerve with a synapse in between.
A reflex action is an involuntary and almost instantaneous movement in response to a stimulus. It usually does not require any thought or input and therefore does not directly involve the brain.
The path taken by the nerve impulses in a reflex action is called a reflex arc. Most reflex arcs involve three neurons. There are two types of reflex arcs namely autonomic reflex arc which involves the inner organs of the body, and somatic reflex arc, which involves muscles.