External stimuli are communicated to the brain by means of electrical signals propagating along nerve cells at a speed of approximately 32 m/s. similarly, electrical messages are sent at the same speed from the brain along nerve cells to the muscles. reflex actions are controlled by a relatively simple nerve circuit from a muscle to the spine and back to the muscle. estimate the reflex time for a stimulus at the knee. (assume that the signal resulting from the stimulus must travel a distance δs = 1 m.