Final answer:
The autonomic nervous system controls involuntary functions like digestion, breathing, and vessel dilation but not voluntary actions such as breath holding which is controlled by the cerebral cortex.
Step-by-step explanation:
The autonomic nervous system (ANS) controls various involuntary functions of the body such as digestion, breathing, vessel dilation for blood flow, and heartbeat regulation but does not control voluntary actions like breath holding. The ANS is divided into the sympathetic and parasympathetic nervous systems, which often have opposing effects on the organs they innervate.
For example, the parasympathetic nervous system is involved in promoting digestion and slowing the heart rate, whereas the sympathetic nervous system prepares the body for 'fight or flight' responses such as increasing the heart rate and dilating airways. However, breath holding is a voluntary action that is not controlled by the ANS but rather by the conscious control of the brain, specifically the cerebral cortex.