The autonomic nervous system, or ANS, is a component of the peripheral nervous system that is responsible for regulating involuntary body functions.

The autonomic nervous system has two main divisions:

  • Sympathetic – regulates the “flight or fight” responses. This division also performs such tasks as relaxing the bladder, speeding up heart rate, and dilating eye pupils.
  • Parasympathetic – helps maintain normal body functions and conserves physical resources. This division also performs such tasks as controlling the bladder, slowing down heart rate, and constricting eye pupils.

After the ANS receives information about the body and external environment, it responds by stimulating body processes.

The ANS controls internal body processes such as the following:

  • Blood pressure
  • Heart and breathing rates
  • Body temperature
  • Digestion
  • Metabolism (thus affecting body weight)
  • The balance of water and electrolytes (such as sodium and calcium)
  • The production of body fluids (saliva, sweat, and tears)
  • Urination
  • Defecation
  • Sexual response
nervous system