Sensory systems are specialized cells of plants and animals sensitive to swift variations in the environment. To Aristotle's five human senses (vision, hearing, taste, smell and touch) comparatively recent research added many more structures with the capacity to react upon internal or external events or stimuli. Beyond his senses man has several extrasensory ways to gather knowledge such as reason, intuition, introspection, the mind's eye and mysticism. The combined activity of sensory systems and the brain leads to assembly of information from the environmental bombardment of 4-D stimuli. This results in experience most of which remains unconscious. As a relatively late spandrel like phenomenon of evolution consciousness arose. This brain's action does not cause consciousness, it ìs consciousness.
