A reflex arc is a neural pathway that controls a reflex action. It typically involves a sensory neuron that detects a stimulus, such as heat or pain, and sends a signal to the spinal cord. In response, the spinal cord activates a motor neuron, which triggers a quick reaction, like pulling your hand away from a hot surface. Reflex arcs are important for protecting the body from harm and enabling quick responses without the need for conscious thought. They often involve sensory neurons, interneurons, and motor neurons, allowing for rapid communication within the nervous system.