Which part of the peripheral nervous system (PNS) is responsible for involuntary movements such as controlling the glands and internal organs?

The autonomic nervous system is the correct choice because it specifically regulates involuntary physiological functions, including the activity of glands, internal organs, and smooth muscle. This system operates without conscious control, managing processes such as heart rate, digestion, and respiratory rate. It is divided into two main branches: the sympathetic nervous system, which prepares the body for stressful situations ("fight or flight"), and the parasympathetic nervous system, which promotes relaxation and energy conservation ("rest and digest").

In contrast, the somatic nervous system is responsible for voluntary movements and the relay of sensory information, while the central nervous system comprises the brain and spinal cord, integrating sensory information and controlling responses. The sympathetic nervous system is just one part of the autonomic nervous system, and does not encompass the entirety of involuntary bodily functions.