In a reflex arc, a stimulus felt by the skin, muscles or organs transmits to the central nervous system (usually the spinal cord). The central nervous system relays the signal to initiate an action from the organism in response to the stimulus.
The reflex arc is a part of the peripheral nervous system and is responsible for actions performed in response to certain stimuli, such as pulling a hand away from a hot object. Its components include a receptor that receives the initial stimulus, such as skin, muscles or organs, a sensory neuron that carries the signal to the central nervous system (the spinal cord), an interneuron that relays the information within the central nervous system, and one or more motor neurons that relay the information to the final component of the arc, the effector. The effector could be a muscle, a gland or both.