The body's functions that occur without conscious effort are regulated by the _________ nervous system.

The autonomic nervous system is responsible for controlling bodily functions that occur automatically and without conscious effort. This includes processes such as heart rate, digestion, respiratory rate, and reflexes. The autonomic system operates independently of the individual's conscious control, allowing the body to maintain homeostasis and respond to internal and external stimuli effectively.

While the sensory nervous system pertains to transmitting sensory information to the central nervous system, and the somatic nervous system controls voluntary muscle movements, these systems involve conscious decision-making and motor control. The voluntary nervous system, as the name implies, requires conscious thought to activate skeletal muscles. Thus, the autonomic nervous system stands out as the correct answer, as it encompasses all functions that the body performs automatically, without the need for conscious awareness.