Autonomic nervous system

The ANS consists of two antagonistic systems:

  • sympathetic:
    • also known as fight or flight
    • increases rate of energy expenditure
    • prepares the body for action
  • parasympathetic:
    • also known as rest and digest
    • decreases rate of energy expenditure
    • the body enters a calm state
Sympathetic (fight or flight)Parasympathetic (rest and digest)
Heart RateIncrease in rate of contraction of cardiac muscle - cardiac output increasesDecrease in rate of contraction of cardiac muscle - cardiac output decreases
Breathing RateSmooth muscle of bronchioles relaxes - intake of air increasesSmooth muscle of bronchioles contracts - intake of air decreases
PeristalsisSmooth muscle of digestive tract contracts less - rate of peristalsis decreasesSmooth muscle of digestive tract contracts more - rate of peristalsis increases
Intestinal SecretionsAction of glands is inhibited - decrease in production of secretionsAction of glands is stimulated - increase in production of secretions