Skip to main content
Medicine LibreTexts

14: Autonomic Nervous System

  • Page ID
  • The autonomic nervous system (ANS) is often associated with the “fight-or-flight response,” which refers to the preparation of the body to either run away from a threat or to stand and fight in the face of that threat with the “rest and digest” which refers to maintaining homeostasis. In this chapter, you will look at the two divisions of the ANS (sympathetic and parasympathetic), their reflexes and the control on the ANS exercised by the central nervous system. 

    • 14.1: Introduction to the Autonomic Nervous System
      The autonomic nervous system is not just about responding to threats. Besides the fight-or-flight response, there are the responses referred to as “rest and digest.” If that lioness is successful in her hunting, then she is going to rest from the exertion. Her heart rate will slow. Breathing will return to normal. The digestive system has a big job to do. Much of the function of the autonomic system is based on the connections within an autonomic, or visceral, reflex.
    • 14.2: Divisions of the Autonomic Nervous System
      The nervous system can be divided into two functional parts: the somatic nervous system and the autonomic nervous system. The somatic nervous system causes contraction of skeletal muscles. The autonomic nervous system controls cardiac and smooth muscle, as well as glandular tissue. The somatic nervous system is associated with voluntary responses and the autonomic nervous system is associated with involuntary responses.
    • 14.3: Autonomic Reflexes
      The autonomic nervous system regulates organ systems through circuits that resemble the reflexes described in the somatic nervous system. The main difference between the somatic and autonomic systems is in what target tissues are effectors. Somatic responses are solely based on skeletal muscle contraction. The autonomic system, however, targets cardiac and smooth muscle, as well as glandular tissue.
    • 14.4: Integration of Autonomic Function
      Autonomic control is based on the visceral reflexes, composed of the afferent and efferent branches. These homeostatic mechanisms are based on the balance between the two divisions of the autonomic system, which results in tone for various organs that is based on the predominant input from the sympathetic or parasympathetic systems. Coordinating that balance requires integration that begins with forebrain structures like the hypothalamus and continues into the brainstem and spinal cord.