Autonomic division of peripheral nervous system

The autonomic nervous system (ANS), formerly referred to as the vegetative nervous system, is a division of the peripheral nervous system that supplies smooth muscle and glands, and thus influences the function of internal organs.

The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions, such as the heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal.

This system is the primary mechanism in control of the fight-or-flight response.

The autonomic nervous system is regulated by integrated reflexes through the brainstem to the spinal cord and organs.

Autonomic functions include control of respiration, cardiac regulation (the cardiac control center), vasomotor activity (the vasomotor center), and certain reflex actions such as coughing, sneezing, swallowing and vomiting.

Those are then subdivided into other areas and are also linked to autonomic subsystems and the peripheral nervous system.

The hypothalamus, just above the brain stem, acts as an integrator for autonomic functions, receiving autonomic regulatory input from the limbic system.

The autonomic nervous system has three branches:

the sympathetic nervous system, the parasympathetic nervous system and the enteric nervous system.

Some textbooks do not include the enteric nervous system as part of this system.

The sympathetic nervous system is often considered the "fight or flight" system, while the parasympathetic nervous system is often considered the "rest and digest" or "feed and breed" system.