Science
How does a reflex work?
A reflex works as an automatic, near-instant response to a stimulus that bypasses conscious thought. When you touch something hot, signals shortcut through your spinal cord to pull your hand away before your brain even registers the pain.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how a reflex works.
Step by step
- 1A sensor detects a stimulus, like heat or a tap.
- 2The signal travels to the spinal cord, not all the way to the brain first.
- 3The spinal cord sends an immediate command back to the muscles.
- 4You react before consciously feeling it — saving crucial time.
- 5This shortcut is called a reflex arc.
Frequently asked questions
- Why are reflexes so fast?
- They skip the brain's slower decision-making, routing the signal through the spinal cord straight back to the muscles.
- What is a reflex arc?
- The short nerve pathway of a reflex: sensor to spinal cord to muscle, which produces a response before conscious thought.
- Why does the doctor tap your knee?
- It triggers a stretch reflex; a normal kick shows the nerve pathway from leg to spinal cord and back is working.