Video narration
How can your hand pull away from something hot before you even feel the pain? Touch a hot object, and receptors in your skin detect heat. This reflex action is rapid and automatic, not a conscious decision. The signal travels along a sensory neuron to the spinal cord. A relay neuron passes it to a motor neuron, carrying the command to the muscles. They contract, and your hand jerks away. Here's the key: the brain is not the first stop. The spinal cord connects the incoming signal to the outgoing muscle command, making the response fast. This route is the reflex arc. Your brain still receives the signal, so you become aware of the pain, but the protective movement has already begun. So why does your hand move before you consciously feel it? Because the reflex arc sends the signal through the spinal cord to your muscles first.