The autonomic nervous system is divided into two primary components: the sympathetic division and the parasympathetic division. These divisions work together to maintain a balance known as autonomic tone, responding dynamically to environmental stimuli and emotional states. When faced with stress or perceived threats, the sympathetic division becomes dominant, activating the body's fight or flight response. This physiological reaction mobilizes energy resources, preparing the body to confront danger or escape from it. For instance, during a stressful situation like an important presentation, the sympathetic system triggers similar responses as it would in a life-threatening scenario, such as increased heart rate and heightened alertness.

In addition to responding to stress, the sympathetic division plays a crucial role in maintaining homeostasis during physical activities. For example, during a soccer or basketball game, it ensures that the body remains physiologically aroused, facilitating increased blood flow to muscles and enhanced oxygen intake.

Conversely, the parasympathetic division is activated during periods of relaxation and calmness, often referred to as the rest and digest system. This division is essential for promoting healthy digestion and maintaining homeostasis when the body is at rest. It works to lower heart rate, slow breathing, and redirect energy towards digestive processes.

Both divisions innervate the same organs but typically have opposing effects. For example, while the sympathetic division increases heart rate, the parasympathetic division decreases it. Understanding the interplay between these two systems is vital for comprehending how the body responds to various stimuli and maintains balance in different states of activity and rest.