The human body is composed of one nervous system that can be subdivided into a central nervous system (CNS) and a peripheral nervous system (PNS) (see figure below). The actions on your heart, lungs, pupils, digestive system, and urinary system have occurred without your conscious awareness and are controlled involuntarily by the autonomic nervous system ( ANS). During this response, your nervous system also slows down organs of digestion, urination, and defecation, so that all available energy may be used for running away. seeing the bear, hearing the bear, and maybe even smelling the bear).
Your body's reactions to the bear can be summed up as a "fright, flight, or fight" reaction elicited by your central nervous system in response to incoming sensory information from the environment (i.e. Almost instantly your pupils dilate, your heart begins racing, the hair on the back of your neck stands up, and you feel a surge of energy as your adrenaline rises and you high tail it in the opposite direction. Thirty minutes into the hike you are confronted by a giant, grizzly mama bear and her cubs. The weekend you've been anticipating for months is finally here-the big hiking trip with your pals in Grand Teton National Park. ORGANIZATION OF THE NERVOUS SYSTEM INTRODUCTION