The reflex arc: pulling away from a hot pan

A reflex action is a fast, automatic response that protects the body, such as pulling your hand away from something hot or blinking when dust flies at your eye. The pathway is called a reflex arc. A receptor detects the stimulus and starts an electrical impulse. A sensory neuron carries it to the spinal cord, where a relay neuron passes it straight to a motor neuron. The motor neuron carries the impulse to an effector, a muscle, which contracts to make the response. Because the impulse does not have to go to the brain first, the reflex is very quick; the brain finds out a moment later and you feel the pain.