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"So there may be an input that isnt strong enough to cause a reaction/output. Otherwise an organism would constently be reacting, and having an output for every small input that occurs."

     When you think about it though, this is exactly what occurs in the body.  In our last class, Prof. Grobstein described an input or perception as a pattern of activity in sensory neurons, and an output or reaction as a pattern of activity in motor neurons.  Unless a person is completely isolated from all possible stimuli, sensory neurons will experience some kind of activity, even if the person is unaware of it.  For example, our bodies are constantly sensing the temperature of the room that we are in, and regulating internal temperature accordingly, even if we "think" that we have adjusted to the room, and ceased to be aware of how warm/cold it is. 

     Another thing that comes to mind is the phenomenon of "spinal shock" that came up during the paralysis discussion.  As I understand it, spinal shock is the period of time following the severing of the spinal chord during which it adjusts to a LACK of signals from the upper portions of the nervous system.  Such a severe reaction to a disruption of signals (signals that the person was probably "unaware" of) shows that it is quite possible for nervous system activity to go unnoticed by the person, or organism, in whom the signals are being transmitted.