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 muscle contraction, allowing the body to react swiftly without needing to think about it. This process usually bypasses the brain for speed, making reflexes faster than voluntary movements. Common examples of reflex arcs include the knee-jerk reaction and the withdrawal reflex when touching something hot. These automatic responses help protect the body from harm.