Final answer:
Reflex arcs are rapid because they involve local synaptic connections and bypass the brain. This saves time in potentially dangerous situations. For example, when touching a hot object, the reflex arc allows the hand to quickly withdraw without conscious thought.
Step-by-step explanation:
Reflex arcs are rapid because they involve local synaptic connections. When a sensory message meets certain parameters, the spinal cord initiates an automatic reflex, bypassing the brain. Messages don't have to travel all the way to the brain, be processed, and sent back, saving precious time in potentially dangerous situations. For example, when you accidentally touch a hot object, the reflex arc allows your hand to quickly withdraw without conscious thought.