The nervous system of the sea turtle is composed of the brain, nerves and spinal cord. In addition, specialized cells called neurons are the signal transmitters throughout the system. The brain is the center of a sea turtle's nervous system and it is there that the impulses carried by the nerves from the sensory organs are processed.  Although the brain of turtles is more advanced than an amphibian's it is primitive in regards to birds and mammals. The spinal cord of the turtle extends down it's back and is protected by the carapace vertebrae.  It is through the spinal cord that the information is carried to and from the brain. Turtles exhibit all the same senses as most organisms but the sense of smell is most advanced. Sea turtles even have the ability to smell underwater. (Dawson 2000).