The esophagus is surrounded by a central nerve ring, which sends nerves into each of the arms, often parallel with the branches of the water vascular system. These all connect to form a brain. They are sensitive to touch, light, temperature,, and water around them. The tube feet, spines, and pedicellariae found on starfish are sensitive to touch, while eyespots on the ends of the rays are light sensitive. The tube feet, especially those at the tips of the rays, are also sensitive to chemicals.