What is the part of the nervous system that controls involuntary activities such as heart rate and digestion called?

The part of the nervous system responsible for controlling involuntary activities, such as heart rate, digestion, and other essential bodily functions, is known as the Autonomic Nervous System. This system operates automatically and is divided into two main branches: the sympathetic and parasympathetic nervous systems. The sympathetic division typically prepares the body for "fight or flight" responses, increasing heart rate and redirecting blood flow, while the parasympathetic division promotes "rest and digest" activities, slowing the heart rate and facilitating digestion.

In contrast, the Central Nervous System consists of the brain and spinal cord, which are primarily involved in processing sensory information and coordinating voluntary movement. The Peripheral Nervous System includes all the nerves outside the central nervous system, serving as a communication link between the CNS and the rest of the body but does not specifically control involuntary functions. The Somatic Nervous System is responsible for voluntary movements and reflex actions, which are under conscious control. Thus, the Autonomic Nervous System is the correct answer, as it specifically regulates involuntary activities critical to maintaining homeostasis.