The system that controls processes such as balance of hormones, temperature, and the width of blood vessels is called the Autonomic Nervous System. This system is responsible for regulating the body's internal organs and maintaining homeostasis. It is divided into two branches: the sympathetic nervous system, which is responsible for the "fight or flight" response, and the parasympathetic nervous system, which is responsible for the "rest and digest" response. The autonomic nervous system controls functions such as blood pressure, heart rate, and digestion, among others.