Touch something hot and your hand yanks back before you even think — the signal raced up nerves, through the spinal cord, and back. The nervous system is the body's wiring, firing electrical messages faster than thought.
The body's electrical network
Neurons are cells that carry electrical signals. Sensory neurons report from the skin and eyes; motor neurons command muscles. The brain interprets and decides, while the spinal cord relays signals and handles fast reflexes without waiting for the brain.
In a reflex arc, the signal loops through the spinal cord straight back to the muscle, skipping the slower trip to the brain. That's why you pull your hand off a hot stove before you feel the pain.
- Touch something sharp: which neuron fires first?
- Follow the signal to the spinal cord.
- Trace the command back out to the muscle.
What you should see: Sensory neuron → spinal cord → motor neuron → muscle. The brain is informed after, which is why the withdrawal comes before the 'ouch'.