Central Nervous System (CNS): The part of the nervous system consisting of the brain and spinal cord.
Peripheral Nervous System (PNS): The part of the nervous system that lies outside the central nervous system.
Parasympathetic Nerves: Branches of the PNS that conserve energy by slowing down the heart rate and increasing intestinal and gland activity.
Sympathetic Nerves: Branches of the PNS that prepare the body for intense physical activity and are often referred to as the fight-or-flight response.