The three stages in the processing of information by the nervous system are the sensory input, the integration and the motor output.
During the sensory output, the sensory neurons carries information for the external stimuli such heat, smell and tastes, and other internal conditions, to the central nervous system for processing. The the CNS analyzes and interprets the input from the sensory neuron and then decides how to respond to the stimuli. Then the motor neuron carries the information from the CNS to the effector cells , that is the muscles and the endocrine glands which then exert the output.
