Which branch of the Peripheral Nervous System is concerned with the internal environment?

• A. Central Nervous System
• B. Peripheral Nervous System
• C. Somatic
• D. Autonomic

Answer: (D)

Regulating the internal environment is done by the autonomic nervous system, a part of the peripheral nervous system that controls involuntary functions of viscera, smooth muscle, and glands. It keeps the body's internal milieu stable by adjusting heart rate, digestion, respiration, pupil size, and gland secretions, all without requiring conscious input. Its sympathetic and parasympathetic divisions work in concert to meet current needs—speeding things up in readiness for action, or promoting quiet, restorative activities. In contrast, the central nervous system (the brain and spinal cord) isn’t a peripheral branch, and the somatic system governs voluntary control of skeletal muscles and conscious sensation, not the regulation of the internal environment.