What does the autonomic nervous system control?

The autonomic nervous system is primarily responsible for controlling involuntary bodily functions that are essential for survival and homeostasis. This includes the regulation of cardiac muscle, which makes up the heart, and smooth muscles, which are found in various organs and structures throughout the body. These involuntary actions include heartbeat regulation, blood vessel contraction, digestion, and respiratory rates.

While voluntary muscle movements are controlled by the somatic nervous system, and maintenance of posture generally involves both voluntary and involuntary systems, neither of these falls under the direct control of the autonomic nervous system. Reflex actions are typically mediated by the spinal cord and brain, activating muscles and glands in response to a stimulus, again not specifically tied to the autonomic control. Therefore, the correct answer highlights the autonomic nervous system's crucial role in managing bodily functions that occur without conscious thought, focusing on the heart and various smooth muscles.