1- Receptor cells in sense organs detect stimuli (change in the surrounding of the body) 2- A receptor cell produces electrical impulses that travel along nerve cells in nerve to the spinal cord, and then usually to the brain 3- The brain processes the information in the impulses 4- The brain sends electrical impulses through nerves in the spinal cord to effectors such as muscles and glands 5- Muscles respond to impulses by contracting; glands respond by releasing hormones