If you sit in a chair with your legs bent, toes not touching the floor, and tap your knee just below your kneecap, the bottom half of your leg gives a little kick. Hold your hand to a flame and your arm recoils. Present a puff of air to your cornea and you blink. Each of these examples is a reflex: sensation leading directly to motion. Reflexes in your peripheral nervous system have sensory neurons wired directly to motor neurons. We call the resulting actions “involuntary” because there is one, and only one, specific behavior for a specific sensory stimulation due to the direct wiring.11
