What system consists of the parasympathetic and sympathetic branches and facilitates communication between non-skeletal muscles and internal organs?

The autonomic nervous system is the correct answer because it specifically regulates involuntary functions within the body, managing the activity of non-skeletal muscles, glands, and internal organs. This system operates without conscious control and is divided into two branches: the sympathetic branch, which prepares the body for 'fight or flight' responses during stressful situations, and the parasympathetic branch, which promotes 'rest and digest' activities when the body is at rest. Together, these systems ensure that essential bodily functions such as heart rate, digestion, and respiratory rate are maintained according to the body's needs.

The central nervous system primarily consists of the brain and spinal cord and is responsible for processing and transmitting information but does not facilitate direct communication with non-skeletal muscles or organs. The peripheral nervous system includes all nerves outside the central nervous system and encompasses both the autonomic and somatic nervous systems. The somatic nervous system, on the other hand, controls voluntary movements of skeletal muscles and is not involved in regulating the functions of internal organs. Therefore, the autonomic nervous system is the specialized system focused on involuntary control of physiological processes.