Which two primary branches comprise the autonomic nervous system?

The autonomic nervous system is primarily composed of two branches: the sympathetic and parasympathetic systems. The sympathetic nervous system is responsible for the body's 'fight or flight' responses, preparing it for action during stressful situations by increasing heart rate, dilating bronchial passages, and inhibiting digestion. On the other hand, the parasympathetic nervous system supports 'rest and digest' activities, promoting relaxation and energy conservation by slowing the heart rate, enhancing digestion, and facilitating body maintenance functions.

Understanding these two branches helps to illustrate how the autonomic nervous system regulates involuntary functions and maintains homeostasis within the body, responding appropriately to changing internal and external environments. The other options do not accurately represent the subdivisions of the autonomic nervous system.