Final answer:
The sympathetic nervous system prepares the body for emergency 'fight-or-flight' responses, activating changes like increased heart rate and adrenaline release.
Step-by-step explanation:
The part of the nervous system that prepares the body to deal with an emergency is the sympathetic nervous system. When you are faced with a stressful situation, your sympathetic nervous system triggers the fight-or-flight response, increasing your heart rate, dilating your pupils, and causing your adrenal glands to release adrenaline, among other physiological changes. This is opposed to the parasympathetic nervous system, which is responsible for resting and digesting activities.
The autonomic nervous system includes both the sympathetic and parasympathetic nervous systems and controls unconscious body functions. The nervous system is wonderfully complex, with the central nervous system (comprised of the brain and spinal cord) and the peripheral nervous system, which includes the autonomic and sensory-somatic nervous systems.