Which division of the autonomic nervous system calms the body and promotes rest?

The division of the autonomic nervous system that calms the body and promotes rest is the parasympathetic nervous system. This system is often referred to as the "rest and digest" system, as it is primarily responsible for conserving energy and facilitating bodily functions that occur when the body is at rest.

When the parasympathetic nervous system is activated, it induces a variety of physiological responses that help to promote relaxation, such as decreasing heart rate, reducing blood pressure, and stimulating digestive processes. For example, following a meal, the parasympathetic system helps the body focus on digestion and absorption of nutrients, thereby enhancing overall metabolic efficiency in a restful state.

The sympathetic nervous system, in contrast, is responsible for the "fight or flight" response, preparing the body for situations that require quick reactions and increased energy expenditure. Meanwhile, the somatic nervous system primarily controls voluntary movements and sensory information from the external environment, and the central nervous system consists of the brain and spinal cord, which processes and integrates information but is not directly responsible for the calming effects of the autonomic systems.