The autonomic nervous system (ANS) is a part of the nervous system that controls involuntary functions in the body, such as heart rate, digestion, and breathing. It operates automatically, meaning we don't have to think about these processes for them to happen. The ANS is divided into two main branches: the sympathetic and parasympathetic systems, which work together to maintain balance in the body. The sympathetic system prepares the body for "fight or flight" responses during stressful situations, while the parasympathetic system promotes "rest and digest" activities when the body is relaxed. Together, these systems help regulate essential functions, ensuring our bodies respond appropriately to different situations.