In the autonomous case we use acetylcholine as well as in some cases epinephrine and norepinephrine. So now let's discuss the sympathetic and the parasympathetic divisions of the autonomic nervous system. Now let's begin with our sympathetic case. Let's suppose we're casually walking in the park and all of a sudden we have a dog that begins to chase us. Now, if we choose to run away from that dog or if we choose to fight that dog off, in either case it's the sympathetic nervous system that actually kicks in. So let's suppose we decide to run away.