The PNS helps to maintain internal balance, or "homeostasis," by the Parasympathetic division of the Autonomic Nervous System (ANS). Sometimes referred to as the "rest and digest" system, the Parasympathetics keep our internal activities regular throughout the day and night, such as a steady heart rate, slow breathing, digestion of food, filtration of blood, and excretion of wastes.
It means they constantly interact with each other and with their environment and are dependent upon each other for survival.
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