Primate sensory systems
share elements across many species of mammals and more.
all involve sensory transduction--transforming specific stimuli such as movement, molecules, light...-into neural impulses transmitted to the brain for integration and interpretation.
adaptively significant inputs tend to use up a lot of brain space
receptors may report external (sound, smell..) and internal (blood pressure, proprioception...) conditions.
receptors may combine in cross-model, multisensory patterns
e,g, eyes may move toward source of sound

                                     receptor neurons                                

the end  
read more about basic sensory functions.